工程日志🛠

参数取值范围错误

使用 CLion，强烈推荐，比 Qt Creator 好用。调试终止在 solvePnPRansac 函数：

OpenCV Error: Assertion failed (confidence > 0 && confidence < 1) in run, file /Users/zhangjixiang/Downloads/opencv-3.3.1/modules/calib3d/src/ptsetreg.cpp, line 178`
`libc++abi.dylib: terminating with uncaught exception of type cv::Exception: /Users/zhangjixiang/Downloads/opencv-3.3.1/modules/calib3d/src/ptsetreg.cpp:178: error: (-215) confidence > 0 && confidence < 1 in function run

程序源码：

cv::solvePnPRansac( pts_obj, pts_img, cameraMatrix, cv::Mat(), rvec, tvec, false, 100, 1.0, 100, inliers );

错误原因：参数 confidence 超出了 (0, 1) 范围。

程序改为：

cv::solvePnPRansac( pts_obj, pts_img, cameraMatrix, cv::Mat(), rvec, tvec, false, 100, 1.0, 0.99, inliers );

可正常运行。

多余的括号

Bug来源：多余的括号

string value = str.substr((pos+1, str.length()));

运行时错误：

OpenCV Error: Assertion failed (npoints >= 4 && npoints == std::max(ipoints.checkVector(2, 5), ipoints.checkVector(2, 6))) in solvePnPRansac, file /Users/zhangjixiang/Downloads/opencv-3.3.1/modules/calib3d/src/solvepnp.cpp, line 252
libc++abi.dylib: terminating with uncaught exception of type cv::Exception: /Users/zhangjixiang/Downloads/opencv-3.3.1/modules/calib3d/src/solvepnp.cpp:252: error: (-215) npoints >= 4 && npoints == std::max(ipoints.checkVector(2, 5), ipoints.checkVector(2, 6)) in function solvePnPRansac

程序可修改为：

string value = str.substr(pos+1, str.length());

macOS 线程与 UI

导致异常的代码：

pcl::visualization::CloudViewer viewer("viewer");
viewer.showCloud(output);
while(!viewer.wasStopped())
{

}

运行时出错提示：

2018-01-31 19:30:31.598 joinPointCloud[57826:4712504] *** Assertion failure in +[NSUndoManager _endTopLevelGroupings], /BuildRoot/Library/Caches/com.apple.xbs/Sources/Foundation/Foundation-1450.16/Foundation/Misc.subproj/NSUndoManager.m:361
2018-01-31 19:30:31.599 joinPointCloud[57826:4712504] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '+[NSUndoManager(NSInternal) _endTopLevelGroupings] is only safe to invoke on the main thread.'
*** First throw call stack:
(
 0   CoreFoundation                      0x00007fff551cc00b __exceptionPreprocess + 171
 1   libobjc.A.dylib                     0x00007fff7be59c76 objc_exception_throw + 48
 2   CoreFoundation                      0x00007fff551d1da2 +[NSException raise:format:arguments:] + 98
 3   Foundation                          0x00007fff572de260 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 193
 4   Foundation                          0x00007fff5726cdb4 +[NSUndoManager(NSPrivate) _endTopLevelGroupings] + 469
 5   AppKit                              0x00007fff5271de56 -[NSApplication run] + 997
 6   libpcl_visualization.1.8.dylib      0x0000000105611c50 _ZN3pcl13visualization13PCLVisualizer8spinOnceEib + 318
 7   libpcl_visualization.1.8.dylib      0x00000001056323a1 _ZN3pcl13visualization11CloudViewer16CloudViewer_implclEv + 699
 8   libboost_thread-mt.dylib            0x00000001017902ac _ZN5boost12_GLOBAL__N_1L12thread_proxyEPv + 156
 9   libsystem_pthread.dylib             0x00007fff7ccd46c1 _pthread_body + 340
 10  libsystem_pthread.dylib             0x00007fff7ccd456d _pthread_body + 0
 11  libsystem_pthread.dylib             0x00007fff7ccd3c5d thread_start + 13
)
libc++abi.dylib: terminating with uncaught exception of type NSException

解决方法：用PCLVisualizer代替CloudViewer

#include <pcl/visualization/pcl_visualizer.h>
...
pcl::visualization::PCLVisualizer viewer("viewer");
viewer.addPointCloud<pcl::PointXYZRGBA>(output);
while(!viewer.wasStopped())
{
 viewer.spinOnce();
}

类似的错误同样发生在ORB_SLAM2

auto resultFuture = async(launch::async, processing, argv, &SLAM);

异常原因：

线程Thread
UI

PCL 显示问题

导致异常的代码：

pcl::visualization::CloudViewer viewer("viewer");
...
if ( visualize == true )
 viewer.showCloud( cloud );

解决方法：用PCLVisualizer代替CloudViewer

参考程序：

pcl::visualization::PCLVisualizer viewer("viewer");
...
if ( visualize == true )
{
 viewer.removeAllPointClouds();
 viewer.addPointCloud( cloud, "hello");
 viewer.updatePointCloud( cloud, "hello" );
 viewer.spinOnce(0.0000000000001);
}

附赠一个bug：漏写函数返回值，运行时异常停止，提示函数的参数错误：

OpenCV Error: Assertion failed (npoints >= 4 && npoints == std::max(ipoints.checkVector(2, 5), ipoints.checkVector(2, 6))) in solvePnPRansac, file /Users/zhangjixiang/Downloads/opencv-3.3.1/modules/calib3d/src/solvepnp.cpp, line 252
libc++abi.dylib: terminating with uncaught exception of type cv::Exception: /Users/zhangjixiang/Downloads/opencv-3.3.1/modules/calib3d/src/solvepnp.cpp:252: error: (-215) npoints >= 4 && npoints == std::max(ipoints.checkVector(2, 5), ipoints.checkVector(2, 6)) in function solvePnPRansac

修改建议：

inline static CAMERA_INTRINSIC_PARAMETERS getDefaultCamera()
{
    ParameterReader pd;
    CAMERA_INTRINSIC_PARAMETERS camera;
    camera.fx = atof(pd.getData("camera.fx").c_str());
    camera.fy = atof(pd.getData("camera.fy").c_str());
    camera.cx = atof(pd.getData("camera.cx").c_str());
    camera.cy = atof(pd.getData("camera.cy").c_str());
    camera.scale = atof(pd.getData("camera.scale").c_str());
    return camera;// Bug
}

用好调试器 lldb/gdb

CLion IDE 优点和缺点一样明显：

代码补全
支持CMake
跳转
方便代码查看
慢，不能容忍！

故提出替代方案：CMake + GCC + LLDB + Sublime Text

替代方案的优点：

快，爽！
灵活
支持基本调试功能

IDE 不过是偷偷地帮你调用了 GCC，LLDB……

调试方法

$ gdb ./my_program          # Start GDB on your program
> run                       # Start running your program
...                         # Now reproduce the crash!
> bt                        # Obtain the backtrace

资料与参考文献：

The LLDB Debugger

编译器优化

slambook/project/0.4/CMakeLists.txt

set( CMAKE_BUILD_TYPE "Debug" )
set( CMAKE_CXX_FLAGS "-std=c++11 -march=native -O3" )

导致运行时错误

Assertion failed: (( ((internal::UIntPtr(m_data) % internal::traits<Derived>::Alignment) == 0) || (cols() * rows() * innerStride() * sizeof(Scalar)) < internal::traits<Derived>::Alignment ) && "data is not aligned"), function checkSanity, file /usr/local/include/eigen3/Eigen/src/Core/MapBase.h, line 191.

修改CMakeLists.txt为

set( CMAKE_BUILD_TYPE "Release" )
set( CMAKE_CXX_FLAGS "-std=c++11" )

可正常运行。原因：编译器优化导致的内存对齐错误？

但运行终止于

****** loop 347 ******
extract keypoints cost time: 0.008442
descriptor computation cost time: 0.008491
good matches: 10
match cost time: 0.001327
pnp inliers: 8
T_c_w_estimated_:
-0.0794355  -0.220607   0.972123    2.80445
 0.0189232   0.974695   0.222737    4.95924
  -0.99666  0.0360889 -0.0732508  -0.908356
         0          0          0          1
reject because inlier is too small: 8
VO costs time: 0.021043

****** loop 348 ******
extract keypoints cost time: 0.009256
descriptor computation cost time: 0.007454
good matches: 2
match cost time: 0.000996
OpenCV Error: Assertion failed (npoints >= 4 && npoints == std::max(ipoints.checkVector(2, 5), ipoints.checkVector(2, 6))) in solvePnPRansac, file /Users/zhangjixiang/Downloads/opencv-3.3.1/modules/calib3d/src/solvepnp.cpp, line 252
libc++abi.dylib: terminating with uncaught exception of type cv::Exception: /Users/zhangjixiang/Downloads/opencv-3.3.1/modules/calib3d/src/solvepnp.cpp:252: error: (-215) npoints >= 4 && npoints == std::max(ipoints.checkVector(2, 5), ipoints.checkVector(2, 6)) in function solvePnPRansac

原因：匹配点数目不够导致的程序终止。

Solution：增加匹配数目，将 100 增加为 200

if ( match_2dkp_index_.size() < 200 )
        addMapPoints();

OpenGL 头文件

#if defined(__APPLE__)
#include <OpenGL/gl.h>
#include <OpenGL/glu.h>
#else
#include <GL/gl.h>
#include <GL/glu.h>
#endif

LaTeX 排版技巧

插入源代码

\usepackage{listings}
\usepackage{xcolor}
\lstset{
% numbers=left,
 numberstyle= \tiny,
 keywordstyle= \color{ blue!70},
 commentstyle= \color{red!50!green!50!blue!50},
 frame=shadowbox, % 阴影效果
 rulesepcolor= \color{ red!20!green!20!blue!20} ,
 escapeinside=``, % 英文分号中可写入中文
% xleftmargin=2em,xrightmargin=2em, aboveskip=1em,
% framexleftmargin=2em
}
...
\begin{lstlisting}
Hello World!
\end{lstlisting}
...

插入参考文献

\cite{...}
...
\bibliographystyle{ieeetr}
\bibliography{name-of-bibtex-file}

插入摘要关键字

\usepackage{abstract}
\providecommand{\keywords}[1]{\textbf{\textit{Index terms---}} #1}
...
\begin{abstract}
There is the abstract...
\end{abstract}
\begin{keywords}
Some keywords...
\end{keywords}

正下方插入文字

\mathop{XXX}\limits_{XXX}

subfigures 插图

\documentclass{article}
\usepackage{graphicx}
\usepackage{caption}
\usepackage{subcaption}
\begin{document}
    \begin{figure}
        \centering
        \begin{subfigure}{0.4\textwidth} % width of left subfigure
            \includegraphics[width=\textwidth]{rncalt.png}
            \caption{RNC} % subcaption
        \end{subfigure}
        \vspace{1em} % here you can insert horizontal or vertical space
        \begin{subfigure}{0.4\textwidth} % width of right subfigure
            \includegraphics[width=\textwidth]{dncalt.png}
            \caption{DNC} % subcaption
        \end{subfigure}
        \caption{Wordcloud of national conventions} % caption for whole figure
    \end{figure}
\end{document}

大括号方程组

\begin{equation}
\left\{
\begin{aligned}
a_{x}&=K_{A}\theta_{x}+K_{AV}\dot{\theta}_{x}+K_{T}(x-x_{0})+K_{V}v_{x}\\
a_{y}&=K_{A}\theta_{y}+K_{AV}\dot{\theta}_{y}+K_{T}(y-y_{0})+K_{V}v_{y}
\end{aligned}
\right.
\end{equation}

收藏链接目录

\usepackage{hyperref}

文中添加横线

\rule{\textwidth}{1mm}

插入空行

\vspace{3ex}

表格线加粗

\usepackage{booktabs}
\toprule[2pt]
\midrule[1pt]

\bottomrule[2pt]

下括号

\underbrace{\frac{\Delta x_1}{\Delta p_1}}_{\text{Tot eff}}

左上标

{}^{e}\dot{p}

计算运行时间(单线程)

#include <ctime>
...
clock_t time_stt = clock(); // 计时
...
cout <<"time use is " << 1000* (clock() - time_stt)/(double)CLOCKS_PER_SEC << "ms"<< endl;

C++ 多线程计时勿用 clock()

clock()函数的功能: 这个函数返回从“开启这个程序进程”到“程序中调用C++ clock()函数”时之间的CPU时钟计时单元（clock tick）数当程序单线程或者单核心机器运行时，这种时间的统计方法是正确的。但是如果要执行的代码多个线程并发执行时就会出问题，因为最终end-begin将会是多个核心总共执行的时钟嘀嗒数，因此造成时间偏大。

Solution

#include <chrono>
std::chrono::steady_clock::time_point t1 = std::chrono::steady_clock::now();
...
std::chrono::steady_clock::time_point t2 = std::chrono::steady_clock::now();
        chrono::duration<double> time_used = chrono::duration_cast<chrono::duration<double>>( t2-t1 );
        cout<<"time use in Tracking is "<< time_used.count() * 1000 <<"ms "<<endl;

固定翼—恒速—编队与跟踪

孙师兄回国给大家分享他博士期间的科研成果，强调矩阵论的重要性。讲座笔记

https://matheecs.tech/images/20180523.jpeg

第二天上午师兄给课题组组织分享会，几点收获：掌握矩阵和优化，Just do it 赶走拖延症，英语很重要！

双目测距模块实现方案（TODO 暑假）

Zynq + xfOpenCV + Stereo Vision Pipeline
GPU TX2

在此基础上设计一款双目视觉教育机器人。

FPGA重新学习需要时间，但不想在硬件上面花太多时间，还是专注算法和创意。

每一个领域（双目视觉）都是坑，一不小心就跳下去出不来了～

思索 SLAM 的真正目的

生成高精度地图
用于导航，但导航真的需要高精度的地图吗
同理，里程计的高精度对于一般的robot重要吗

或许robot不需要高精度的里程计和地图，robot应更像人一样，而不是机器。

所以想到设计一个 low resolution vision 的 autonomous navigation mobile robot～

OpenCV 3.4 编译

树莓派需要先修改软件源、安装依赖库。

$ cmake \
-DCMAKE_BUILD_TYPE=RELEASE \
-DCMAKE_INSTALL_PREFIX=/usr/local \
-DOPENCV_EXTRA_MODULES_PATH=/Users/zhangjixiang/Downloads/opencv_contrib-3.4.0/modules \
-DWITH_CUDA=OFF \
-DBUILD_DOCS=OFF \
-DBUILD_EXAMPLES=OFF \
-DBUILD_TESTS=OFF \
-DBUILD_PERF_TESTS=OFF \
..

$ make -j4
$ sudo make install

C++11/17 编译命令

clang++ -std=c++11 edX.cpp
clang++ -std=c++17 edX.cpp

Valgrind安装(macOS High Sierra)

$ brew edit valgrind
 'https://sourceware.org/git/valgrind.git'->'git://sourceware.org/git/valgrind.git'
$ brew update
$ brew install --HEAD valgrind

参考 How to Install Valgrind on macOS High Sierra

使用方法

gcc main.cpp -g
valgrind --tool=memcheck --leak-check=full --show-reachable=yes ./a.out

libcreate安装(macOS)

文件 libcreate/src/serial_query.cpp 中

tcflush(port.lowest_layer().native(), TCIFLUSH);

修改为

tcflush(port.lowest_layer().native_handle(), TCIFLUSH);

文件 libcreate/src/data.cpp 中添加

#include <iostream>

否则提示错误

error: no member named 'cout' in namespace 'std'

Google Test安装

make
make install

InstallingGoolgeTestForMac.wiki

LattePanda 启动后显示屏信号中断

推测原因：电流 (1.8A) 不足。

Any standard USB adapter (such as a cell phone wall charger) with at least 2A of current can be used as a power supply for the LattePanda.

LattePanda

Pixhawk 创建 App

添加 CMakeLists.txt 和 C 程序源文件后，需要修改文件：/Firmware/cmake/configs/nuttx_px4fmu-v2_default.cmake

examples/px4_simple_app

MYNTEYE 相机使用参考文件 CMakeLists

cmake_minimum_required(VERSION 2.8)
project(mynteye_sdk_samples)

include(${PROJECT_SOURCE_DIR}/cmake/Common.cmake)
include(${PROJECT_SOURCE_DIR}/cmake/DetectCXX11.cmake)
include(${PROJECT_SOURCE_DIR}/cmake/DetectOpenCV.cmake)

# flags
SET(CMAKE_BUILD_TYPE Release)
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -O3")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -O3")

# variables
set(SDK_DIR /Users/zhangjixiang/mynteye-1.8-mac-x64-opencv-3.4.0)
set(SDK_LIB_DIR ${SDK_DIR}/lib)
set(LIB_MYNTEYE_CORE ${CMAKE_SHARED_LIBRARY_PREFIX}mynteye_core${CMAKE_SHARED_LIBRARY_SUFFIX})

message(STATUS "SDK_DIR: ${SDK_DIR}")
message(STATUS "SDK_LIB_DIR: ${SDK_LIB_DIR}")
message(STATUS "LIB_MYNTEYE_CORE: ${LIB_MYNTEYE_CORE}")

# required
include_directories( ${SDK_DIR}/include )

# camera
add_executable(camera camera.cc)
target_link_libraries(camera
  ${SDK_LIB_DIR}/${LIB_MYNTEYE_CORE}
  ${OpenCV_LIBS}
)

C++ 源代码：

#include <iomanip>
#include <iostream>

#include <opencv2/highgui/highgui.hpp>

#include "camera.h"
#include "utility.h"

using namespace std;
using namespace mynteye;

int main(int argc, char const *argv[]) {
    std::string name;
    if (argc >= 2) {
        name = argv[1];
    } else {
        bool found = false;
        name = FindDeviceName(&found);
    }
    cout << "Open Camera: " << name << endl;

    Camera cam;
    InitParameters params(name);
    cam.Open(params);

    if (!cam.IsOpened()) {
        std::cerr << "Error: Open camera failed" << std::endl;
        return 1;
    }
    std::cout << "\033[1;32mPress ESC/Q on Windows to terminate\033[0m\n";

    double t, fps = 0;
    ErrorCode code;
    cv::Mat img_left;
    for (;;) {
        t = (double)cv::getTickCount();

        code = cam.Grab();

        if (code != ErrorCode::SUCCESS) continue;

        if (cam.RetrieveImage(img_left, View::VIEW_LEFT_UNRECTIFIED) == ErrorCode::SUCCESS)
        {
            // top left: width x height
            stringstream ss;
            ss << img_left.cols << "x" << img_left.rows;
            DrawInfo(img_left, ss.str(), Gravity::TOP_LEFT);
            // top right: fps
            ss.str(""); ss.clear();
            ss << fixed << setw(7) << setprecision(2) << setfill(' ') << fps;
            DrawInfo(img_left, ss.str(), Gravity::TOP_RIGHT);
            cv::imshow("left", img_left);
        }

        char key = (char) cv::waitKey(1);
        if (key == 27 || key == 'q' || key == 'Q') {  // ESC/Q
            cv::imwrite("left.jpg",img_left);
            cout << "Saved Images!" << endl;
            break;
        }

        t = (double)cv::getTickCount() - t;
        fps = cv::getTickFrequency() / t;
    }

    cam.Close();
    cv::destroyAllWindows();
    return 0;
}

在 macOS 上安装 TensorFlow

pip install tensorflow      # Python 2.7; CPU support

Host key verification failed

ssh-keygen -R hostname

禁用 Win10 驱动签名

点击通知，找到并进入“所有设置”
在所有设置中找到并进入“更新和安全”
找到恢复，点击“高级启动”下的“立即重启”，重启电脑
重启后选择“疑难解答”
选择“高级选项”
选择“启动设置”
点击“重启”
按提示输入“7”禁用驱动程序强制签名

用pandoc实现LaTeX转Word

pandoc -s document.tex -o word.docx

LaTeX导入pdf文档

\usepackage{pdfpages}
...
\includepdf[pages=-,pagecommand={},width=\textwidth]{file.pdf}

树莓派软件源配置

$ sudo nano /etc/apt/sources.list

deb http://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/ stretch main non-free contrib
deb-src http://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/ stretch main non-free contrib

Raspbian Lite to Raspbian PIXEL

sudo apt-get install --no-install-recommends xserver-xorg
sudo apt-get install --no-install-recommends xinit
sudo apt-get install raspberrypi-ui-mods
sudo apt-get install lightdm

修改树莓派swap分区大小

$ sudo vim /etc/dphys-swapfile
...
修改 CONF_SWAPSIZE=2048
...
$ sudo /etc/init.d/dphys-swapfile restart

树莓派USB相机驱动

相机设备 /dev/video0

sudo modprobe bcm2835-v4l2

图像窗口打开后马上关闭

if ( (char) cv::waitKey(33) >= 0 )
   break;

修改为：

if ( cv::waitKey(33) >= 0 )
   break;

掌握 gdb 单步调试

打开swf文件

<html>
 <body>
  <embed src="/Users/zhangjixiang/Downloads/dirtran_mintime_double_integrator_fine.swf" width="100%" height="100%"></embed>
 </body>
</html>

Flask + Arduino Web应用程序

import serial
from time import sleep
from flask import request

from flask import Flask
app = Flask(__name__)
ser = serial.Serial('/dev/tty.usbmodem1411', 9600, timeout=1)

@app.route("/", methods = ['POST', 'GET'])
def hello():
 if request.method == 'POST':
  print request.form['submit']
  # ser = serial.Serial('/dev/tty.usbmodem1411', 9600, timeout=1)
  if request.form['submit'] == 'ON':
   print '1'
   ser.write(b'1')
  elif request.form['submit'] == 'OFF':
   print '0'
   ser.write(b'0')
  else:
   pass # unknown
 return '<form action="/" method="POST"><input type="submit" name="submit" value="ON"><input type="submit" name="submit" value="OFF"></form>'

if __name__ == "__main__":
 # app.run()
 app.run(host='0.0.0.0')

Arduino串口测试程序

import serial
import time
from struct import *

mega = serial.Serial(port='/dev/cu.usbmodem1421',
    baudrate=9600, timeout = 3.0)

try:
    while True:
        raw = raw_input('input a char: ')
        mega.write(pack('c',raw))
        # read a '\n' terminated line
        line = mega.readline()
        print line
except Exception as e:
    mega.close()

手动添加Appimage应用图标

需要添加两个文件：文件和图标

/usr/share/applications/xxx.desktop，例如

[Desktop Entry]
Name=KDEnlive
Comment=Non Linear Video Editor
GenericName=Video Editor
Exec=/home/ajith/Applications/Kdenlive-17.12.0d-x86_64.AppImage   #make sure to change the below path to the path in your system
Icon=kdenlive   #the icon name for your application will be different
Type=Application
StartupNotify=true
Categories=Qt;KDE;AudioVideo;AudioVideoEditing;
MimeType=application/x-kdenlive;

/usr/share/icons/hicolor/512x512/apps/xxx.png

利用FileZilla SFTP传文件

SFTP = SSH File Transfer Protocol

打开Ubuntu SSH

sudo apt-get update
sudo apt-get install openssh-server
sudo ufw allow 22

LaTeX 格式转换 Markdown

pandoc -s example4.tex -o example5.text

Bochs启动黑屏

原因：debug模式

Solution：输入c，然后回车执行

<bochs:1> c

Vim 调试：termdebug 入门

ImportError in system pip wrappers after an upgrade

python -m pip uninstall pip

How do you calculate program run time in python?

import timeit
start = timeit.default_timer()

#Statements

stop = timeit.default_timer()
print('Time: ', stop - start)

WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED

ssh-keygen -R <host>

Catch a Ctrl-C Event (C++)

#include <signal.h>
...

void myfunction(int sig) {
  ...
  exit(1);
}

int main(int argc, char** argv) {
  signal(SIGINT, myfunction);
  ...
}

How do I find all files containing specific text on Linux?

查找所有文件中的内容
$ grep -rnw '/path/to/somewhere/' -e 'pattern'
$ grep -Ril "text-to-find-here" /

查找指定文件名
$ find /home/username/ -name "*.err"

设置代理服务器允许局域网的其他设备共享

ss 偏好设置->HTTP->HTTP代理监听地址->修改为0.0.0.0。

代理服务器主机名写运行 ss 的电脑的 IP 地址。

Ubuntu创建sudo用户

sudo adduser username
usermod -aG sudo username
su - username

ROS生成msg/srv/action后编译package

catkin_make messages_generate_messages
catkin_make

Ubuntu系统下查看OpenCV版本

dpkg -l | grep libopencv

查看CUDA版本

nvcc --version

查看CuDNN版本

cat /usr/local/cuda/include/cudnn.h | grep CUDNN_MAJOR -A 2

使用pkg-config

$ pkg-config --cflags librtmp
$ pkg-config --libs librtmp

常用参数：
–-list-all     列出所有已安装的共享库
-–cflags     列出指定共享库的预处理和编译flag
-–libs     列出指定共享库的链接flag

用 Python & matplotlib 绘图

import re
import numpy as np
import matplotlib as mpl
import matplotlib.pyplot as plt

# read the log file
files = ['00.txt', '01.txt', '02.txt', '03.txt']
iters = [8000, 80000, 8000, 20000]
descr = ['00iter: [8000,4000,8000,4000]         base_lr: 0.001', '01iter: [80000,40000,80000,40000] base_lr: 0.0005', '02iter: [8000,4000,8000,4000]         base_lr: 0.0005', '03iter: [20000,10000,20000,10000] base_lr: 0.0005']
color = ['green', 'red', 'skyblue', 'blue']
plt.title('Result Analysis')

for i in range(4):
  file_log = open(files[i], 'r')
  train_iterations = []
  train_loss = []
  for line in file_log:
    if '] Iteration ' in line and 'loss = ' in line:
      arr = re.findall(r'ion \b\d+\b',line)
      train_iterations.append(int(arr[0].strip(',')[4:]))
      train_loss.append(float(line.strip().split(' = ')[-1]))
  file_log.close()
  print len(train_iterations)
  plt.plot(train_iterations[0:iters[i] / 20], train_loss[0:iters[i] / 20], color=color[i], label=descr[i])

plt.legend()
plt.xlabel('iteration times')
plt.ylabel('loss')
plt.xlim(-20, 2000)
plt.show()

用 MATLAB 添加高斯和椒盐噪音

% add gauss and peper noise
% 2019-02-23
clc
clear all

XmlPath = 'dataset/xml/';
XmlFile = dir(fullfile(XmlPath, '*.xml'));
XmlNames = transpose({XmlFile.name});
Amount = size(XmlNames, 1);
PicPath = 'dataset/';

for k = 1:Amount
    filename = fullfile(XmlPath, XmlNames(k));
    XDoc = xmlread(char(filename));
    xmin = XDoc.getElementsByTagName('object').item(0).getElementsByTagName('xmin').item(0).getFirstChild.getNodeValue; xmin = str2num(xmin);
    ymin = XDoc.getElementsByTagName('object').item(0).getElementsByTagName('ymin').item(0).getFirstChild.getNodeValue; ymin = str2num(ymin);
    xmax = XDoc.getElementsByTagName('object').item(0).getElementsByTagName('xmax').item(0).getFirstChild.getNodeValue; xmax = str2num(xmax);
    ymax = XDoc.getElementsByTagName('object').item(0).getElementsByTagName('ymax').item(0).getFirstChild.getNodeValue; ymax = str2num(ymax);
    ap = [xmin, ymin, xmax, ymax]

    XmlName = char(XmlNames(k));
    PicName = strcat(XmlName(1:6), '.jpg');

    origin = imread(PicName);
    % r = [0 ~ 0.2]
    r = randi([0 200],1,3)/1000
    I_0 = imnoise(origin, 'salt & pepper', r(1));
    Im = imnoise(I_0, 'gaussian', r(2), r(3));
    [rNum,cNum] = size(Im);
    x1 = (xmin+xmax)/2; y1 = (ymin+ymax)/2; radius = (xmax+ymax-xmin-ymin)/4;
    [xx,yy] = ndgrid((1:rNum)-y1,(1:cNum)-x1);
    mask = (xx.^2 + yy.^2) >= radius^2+10^2;
    Im(mask) = uint8(0);
    imwrite(Im, fullfile('newdataset/', PicName))
end

C/C++字符串分割

/* strtok example */
#include <stdio.h>
#include <string.h>

int main ()
{
  char str[] ="- This, a sample string.";
  char * pch;
  printf ("Splitting string \"%s\" into tokens:\n",str);
  pch = strtok (str," ,.-");
  while (pch != NULL)
  {
    printf ("%s\n",pch);
    pch = strtok (NULL, " ,.-");
  }
  return 0;
}

Latency Numbers Every Programmer Should Know

Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD
Read 1 MB sequentially from memory     250,000   ns      250 us
Round trip within same datacenter      500,000   ns      500 us
Read 1 MB sequentially from SSD*     1,000,000   ns    1,000 us    1 ms  ~1GB/sec SSD, 4X memory
Disk seek                           10,000,000   ns   10,000 us   10 ms  20x datacenter roundtrip
Read 1 MB sequentially from disk    20,000,000   ns   20,000 us   20 ms  80x memory, 20X SSD
Send packet CA->Netherlands->CA    150,000,000   ns  150,000 us  150 ms

Notes
-----
1 ns = 10^-9 seconds
1 us = 10^-6 seconds = 1,000 ns
1 ms = 10^-3 seconds = 1,000 us = 1,000,000 ns

Credit
------
By Jeff Dean:               http://research.google.com/people/jeff/
Originally by Peter Norvig: http://norvig.com/21-days.html#answers

Contributions
-------------
'Humanized' comparison:  https://gist.github.com/hellerbarde/2843375
Visual comparison chart: http://i.imgur.com/k0t1e.png

用 cloc 统计代码量

prompt> cloc gcc-5.2.0/gcc/c
      16 text files.
      15 unique files.
       3 files ignored.

https://github.com/AlDanial/cloc v 1.65  T=0.23 s (57.1 files/s, 188914.0 lines/s)
-------------------------------------------------------------------------------
Language                     files          blank        comment           code
-------------------------------------------------------------------------------
C                               10           4680           6621          30812
C/C++ Header                     3             99            286            496
-------------------------------------------------------------------------------
SUM:                            13           4779           6907          31308
-------------------------------------------------------------------------------

符号计算小工具 SymPy

SymPy is a Python library for symbolic mathematics. It aims to become a full-featured computer algebra system (CAS) while keeping the code as simple as possible in order to be comprehensible and easily extensible. SymPy is written entirely in Python.

Keynote 中插入高亮代码

brew install highlight
pbpaste | highlight --syntax=c++ -K 17 -u "utf-8" -t 2 -n -O rtf | pbcopy

macOS 终端报错 ValueError: unknown locale: UTF-8

export LC_ALL=en_US.UTF-8
export LANG=en_US.UTF-8

理解 GitHub

https://matheecs.tech/images/Git.jpg

使用 CMake/CPack/CTest/Catkin

IMU模型

https://matheecs.tech/images/imumodel.jpg

安装LaTeX依赖包

sudo tlmgr install name-of-package

学会用 Glog, Gflags, Gtest, Doxygen, GitHub CI/CD, Protobuf, clang-format

解决安装`ros-kinetic-desktop-full`失败

Solution：保留/etc/apt/sources.list默认配置，不要覆盖原有内容

vim中添加`sudo`权限保存文档

:w !sudo tee %

Ubuntu安装中文字体解决PDF文档无法显示

sudo apt-get install language-pack-zh*
sudo apt-get install chinese*
sudo apt-get install fonts-arphic-ukai fonts-arphic-uming fonts-ipafont-mincho fonts-ipafont-gothic fonts-unfonts-core

采用Homebrew国内源

替换brew.git:
cd "$(brew --repo)"
git remote set-url origin https://mirrors.ustc.edu.cn/brew.git

替换homebrew-core.git:
cd "$(brew --repo)/Library/Taps/homebrew/homebrew-core"
git remote set-url origin https://mirrors.ustc.edu.cn/homebrew-core.git

重置

重置brew.git:
cd "$(brew --repo)"
git remote set-url origin https://github.com/Homebrew/brew.git

重置homebrew-core.git:
cd "$(brew --repo)/Library/Taps/homebrew/homebrew-core"
git remote set-url origin https://github.com/Homebrew/homebrew-core.git

zsh + Oh My Zsh

macOS Catalina 开始默认采用 zsh，配合 Oh My Zsh 十分好用。

用终端命令烧录树莓派镜像

sudo diskutil umount /dev/disk2s1
sudo dd bs=8m if=./2019-09-26-raspbian-buster-full.img of=/dev/rdisk2

pip3使用国内源

pip3 config set global.index-url https://pypi.tuna.tsinghua.edu.cn/simple

pypi 镜像使用帮助

使用Miniconda管理Python环境和软件包

Miniconda

# 新建/删除环境
conda create -n env_name python=3.7
conda remove -n env_name --all

# 激活/退出环境
conda activate env_name
conda deactivate

树莓派3b+安装Ubuntu MATE 16.04后出现彩虹屏无法联网？

安装ROS软件包出错提示 The following packages have unmet dependencies: ros-kinetic-

修改软件源配置文件

sudo gedit /etc/apt/sources.list

参考

# deb cdrom:[Ubuntu 16.04.2 LTS _Xenial Xerus_ - Release amd64 (20170215.2)]/ xenial main restricted

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://cn.archive.ubuntu.com/ubuntu/ xenial main restricted
# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://cn.archive.ubuntu.com/ubuntu/ xenial-updates main restricted
# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://cn.archive.ubuntu.com/ubuntu/ xenial universe
# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial universe
deb http://cn.archive.ubuntu.com/ubuntu/ xenial-updates universe
# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://cn.archive.ubuntu.com/ubuntu/ xenial multiverse
# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial multiverse
deb http://cn.archive.ubuntu.com/ubuntu/ xenial-updates multiverse
# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial-updates multiverse

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://cn.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse
# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb http://archive.canonical.com/ubuntu xenial partner
# deb-src http://archive.canonical.com/ubuntu xenial partner

deb http://security.ubuntu.com/ubuntu xenial-security main restricted
# deb-src http://security.ubuntu.com/ubuntu xenial-security main restricted
deb http://security.ubuntu.com/ubuntu xenial-security universe
# deb-src http://security.ubuntu.com/ubuntu xenial-security universe
deb http://security.ubuntu.com/ubuntu xenial-security multiverse
# deb-src http://security.ubuntu.com/ubuntu xenial-security multiverse

最后更新

sudo apt-get update

解决macOS 10.15 软件提示损坏/无法验证开发者等问题

sudo spctl --master-disable

sudo xattr -r -d com.apple.quarantine /XXX/XXX.app/

如何安装 GTest

git clone https://github.com/google/googletest
cd googletest
mkdir build
cd build
cmake ..
make
make install

如何卸载 Java 8

sudo rm -rf /Library/Java/JavaVirtualMachines/jdk<version>.jdk

sudo rm -rf /Library/PreferencePanes/JavaControlPanel.prefPane
sudo rm -rf /Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin
sudo rm -rf /Library/LaunchAgents/com.oracle.java.Java-Updater.plist
sudo rm -rf /Library/PrivilegedHelperTools/com.oracle.java.JavaUpdateHelper
sudo rm -rf /Library/LaunchDaemons/com.oracle.java.Helper-Tool.plist
sudo rm -rf /Library/Preferences/com.oracle.java.Helper-Tool.plist

视频转 GIF 动图

安装软件

brew install ffmpeg
brew cask install xquartz #dependency for gifsicle, only required for mountain-lion and above
open /usr/local/Caskroom/xquartz/2.7.11/XQuartz.pkg
brew install gifsicle

生成GIF

ffmpeg -i in.mov -s 600x400 -pix_fmt rgb24 -r 10 -f gif - | gifsicle --optimize=3 --delay=3 > out.gif

参考：OS X Screencast to animated GIF

安装字体解决 LaTeX 编译错误

SimHei 和 SimSun 可以从 Word 软件中导出安装到 macOS 系统。Word 中自带字体的路径：

/Applications/Microsoft Word.app/Contents/Resources/DFonts

配置 LaTeX + VS Code 环境

Configure Visual Stuido Code as LaTeX IDE

腾讯云域名绑定GitHub博客

腾讯云域名解析配置：

GitHub Pages域名绑定

MacBook开发iOS应用真机调试无需开发者账号

Note that you may have to update “Team” to your own account (General Tab -> Signing in Xcode 10 or “Signing and Capabilities” Tab -> Signing in Xcode 11). Update the Bundle Identifier if needed.

修改部分：

Team: xxxxxx (Personal Team)
Bundle Identifier: xxxxxx.matheecs

如何学习开源项目

安装
运行
原理研究
测试
最后一步研究源码

OmniGraffle 学习资料

Rhino 学习资料

Git 底层原理

这张动态图解来自这才是真正的GIT：GIT原理及实用技巧。

电视直播软件

电视家

macOS 10.15 Catalina xxx.app已损坏，无法打开

sudo spctl --master-disable
sudo xattr -rd com.apple.quarantine /Applications/xxxxxx.app

如何用 GitHub 贡献代码

Fork
Commit & Push
Pull Request
CI

Install gitk on Mac

brew update
brew install git
brew install git-gui

SQ4R学习方法

SQ4R = SURVEY + QUESTION + READ + RECITE + WRITE + REVIEW

淘宝宝贝搜索 URL Scheme

taobao://s.taobao.com/?q=%@

英语口语发音技巧

连读
省略
- t, d, and→n
重读

macOS 上 texstudio 外部pdf浏览器查看可以正常显示中文但内置的pdf浏览器不能显示中文

解决方法，用brew安装poppler库，替换掉texstudio程序包里的库：

/Applications/texstudio.app/Contents/Frameworks/libpoppler.*.dylib
/Applications/texstudio.app/Contents/Frameworks/libpoppler-qt*.*.dylib

一个texstudio的小问题：文字无法显示

如何保护电脑安全？

当你使用一个公共网络时要注意保护自己
换用一个更安全的浏览器
使用一个安全的电子邮件服务商
持续更新软件
选择一些不容易被猜对的密码，并安全存储它们
打开电子邮件附件时是有风险的，要注意防御
别用电话给你不认识的人发信息
谨慎地使用P2P下载
想办法为你的硬盘加密
要时刻保持对社会工程学攻击的警觉性

pip 与 pip3 的区别？

pip3 always operates on the Python3 environment only, as pip2 does with Python2. pip operates on whichever environment is appropriate to the context. For example if you are in a Python3 venv, pip will operate on the Python3 environment

pip install -r requirements.txt

FAT, ExFAT, NTFS 格式

安卓系统默认只能识别 FAT 和 NTFS 格式，但是 macOS 不支持 NTFS 格式，需要安装软件（比如 Paragon NTFS for Mac）。FAT 要求每个文件大小不能超过 4G！

Ignore formula on brew upgrade

brew pin <formula>

反之：

brew unpin <formula>

高版本 OpenCV (> 3.4.2.16) 不提供 SIFT 功能

python -m pip install opencv-python==3.4.2.16
python -m pip install opencv-contrib-python==3.4.2.16

macOS 深度清理

跟着这份清理教程，帮你的 Mac 腾出更多储存空间
Keeping macOS clean: this is my osx/brew/… update CLI command
一款好用又免费的辅助清理软件：OmniDiskSweeper

终端的代理设置

export http_proxy="http://127.0.0.1:8001"
export https_proxy="http://127.0.0.1:8001"

用类似的方法加速 $ git clone ...

git config --global http.proxy 'socks5://127.0.0.1:1080'
git config --global https.proxy 'socks5://127.0.0.1:1080'

取消用

git config --global --unset http.proxy
git config --global --unset https.proxy

FileZilla 传文件居然会改变文件的大小

解决方案：把 ASCII 改为二进制传输！

omg-tools 绘图窗口闪退

解决方案：matplotlib.pyplot.pause(interval)[source]

MATLAB R2020a （macOS Catalina）启动时鼠标卡住

解决方案：先点击 R2020a，再打开任意软件的界面，让 R2020a 在“后台”启动

使用 ROS 的 PCL 库

set(PCL_DIR "/usr/lib/x86_64-linux-gnu/cmake/pcl")   #该路径中存放*.cmake文件
find_package(PCL 1.7 REQUIRED)

macOS Catalina 用 brew 安装 Python

Homebrew provides a formula for Python 3.x (python@3.x). The executables are organised as follows:

python3 points to Homebrew’s Python 3.x (if installed)
pip3 points to Homebrew’s Python 3.x’s pip (if installed)

卸载 CMAKE 安装的软件

cat install_manifest.txt | sudo xargs rm

macOS 语音合成

say 你好 -o out.wave

ROS 节点结束前任务自定义

#include <ros/ros.h>
#include <signal.h>

void mySigintHandler(int sig)
{
  // Do some custom action.
  // For example, publish a stop message to some other nodes.
  
  // All the default sigint handler does is call shutdown()
  ros::shutdown();
}

int main(int argc, char** argv)
{
  ros::init(argc, argv, "my_node_name", ros::init_options::NoSigintHandler);
  ros::NodeHandle nh;

  // Override the default ros sigint handler.
  // This must be set after the first NodeHandle is created.
  signal(SIGINT, mySigintHandler);
  
  //...
  ros::spin();
  return 0;
}

用 Homebrew 安装自己编译的软件包

$ ./configure --prefix=/usr/local/Cellar/foo/1.2
$ make
$ make install
$ brew link foo

# OR

$ cmake .. DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr/local/Cellar/foo/1.2
$ make
$ make install
$ brew link foo

CPU 性能测试

sudo apt install p7zip-full
7z b

用 Backward Debug for C++

#include <ndt_mapping/backward.hpp>

namespace backward {
  backward::SignalHandling sh;
}

ROS 包生成 deb 安装包

CATKIN_PACKAGE_BIN_DESTINATION
CATKIN_PACKAGE_INCLUDE_DESTINATION
CATKIN_PACKAGE_SHARE_DESTINATION

sudo apt-get install python-bloom
cd path/to/your/catkin/package
bloom-generate rosdebian
fakeroot debian/rules binary
bloom-generate rosdebian --os-name ubuntu --os-version xenial --ros-distro kinetic
fakeroot debian/rules binary

TexStudio 预览无法显示中文字体

解决方法1：修改显示字体

\setCJKmainfont{Kaiti TC Regular}
\setCJKsansfont{Songti TC Regular}
\setCJKmonofont{Heiti TC Regular}

解决方法2：把内置的预览器换成外部 PDF 浏览器

Linux 性能分析工具

Steps to create Textured Mesh from Point Cloud using Meshlab

Convert “.pcd” file to “.ply” file

import os
import open3d as o3d

map_pcd_path = str(os.path.dirname(os.path.abspath(__file__))) + "/../map/yuanqu.pcd"
map_ply_path = str(os.path.dirname(os.path.abspath(__file__))) + "/../map/yuanqu.ply"
map_pcd_data = o3d.io.read_point_cloud(map_pcd_path)
o3d.visualization.draw_geometries([map_pcd_data])

o3d.io.write_point_cloud(map_ply_path, map_pcd_data)

Get your PointCloud into MeshLab

Import the pointcloud file in “.ply” file format in Meshlab. Before importing make sure you do some pre-processing / cleaning on point cloud so as to ease the process of meshing.

Point Cloud Simplification and Normals Computation

Next we need to reduce the number of point samples for smooth meshing.
- So go to Filters -> Point Set -> Point Cloud Simplification. Enter Number of samples circa 5% of original number of points. Make sure Best Sample Heuristic is checked.
After point cloud simplification, make sure to select Simplified point cloud in the Show Layer Dialog on the right hand side. If not visible, it can opened by going to View -> Show Layer Dialog. Now we need to compute normals for point set.
- So go to Filters -> Point Set -> Compute normals for point sets . Enter Neighbour num between 10 - 100. Initially try with 10 and try to get a mesh and later see if this can be improved by increasing the neighbour number. For Smooth Iteration initially try with 0 value and may be later it can be tried with values between 5 - 10. I mostly use value 8.
Make sure if your normals are properly computed by going to Render -> Show Normal.

Meshing / Poisson Surface Reconstruction

Next we are going to use Poisson Surface reconstruction to do meshing.
- So go to Filters ->Remeshing, Simplification and Reconstruction -> Screened Poisson Surface Reconstruction. Initially try with default parameters then later one can play around with reconstruction depth, number of samples and interpolation weight values.
- This will create another mesh layer called Poisson in the Show layer Dialog which has surfaces now. Make sure to select that to peform further operations.
- One can observe that it has also created some extra surfaces. To remove them go to Filters -> Selection -> Select Faces with edges longer than …. By deafult the value is automatically computed, just click on apply. Then click on delete face button (triangle face and three vertex with a cross over it). This will remove extra surfaces.
- After this operation, still some noise faces can be seen. To remove them go to Filters -> Cleaning and Repairing -> Remove isolated pieces (wrt Face Num.). Use the default value and make sure Remove unreferenced vertices is checked. This will remove some noise faces.
- Even after the above operation some noise faces are seen. To remove them go to Filters -> Selection -> Select non Manifold Vertices. Click apply. Then click on delete face button (triangle and threwe vertex with a cross over it). This will remove remaining extra faces.

Texturizing the Mesh using pointcloud color attributes

Now that we have a mesh, next step is to get the texture for the mesh from the pointcloud.
Make sure to select Poisson in the Show layer Dialog to peform further operations.
Go to Filters -> Texture -> Per Vertex Texture Function. Click on apply.
Go to Filters -> Texture -> Convert PerVertex UV into PerWedge UV. Click on apply.
Go to Filters -> Texture -> Parametrization: trivial Per-triangle.
- Quads -per -line : 0
- Texture Dimension (px) : 4096 or (1024, 2048).
- Inter-triangle border (px) : 0
- Method : Basic (with Space-optimizing somethimes Meshlab crashes.)
- Click on Apply.
Now go to File -> Save Project As... Save the project in “.mlp” file format.
Now go to File -> Export Mesh As... Save the mesh in “.obj” file format. After clicking on save, it will open saving options. Make sure under Wedge, TexCoord is checked. Then click on OK.
Now go to Filters -> Texture -> Transfer: Vertex Color to Texture.
- Texture file : (If your mesh was saved as mesh_1.obj, the texture file name should be mesh_1.png)
- Texture width (px) : 4096 (make sure this is same as Texture Dimension in the above steps)
- Texture height (px) : 4096 (make sure this is same as Texture Dimension in the above steps)
- Check Assign texture and Fill texture.
- Click on Apply.
Now you have a textured mesh. There is also a texture image file saved in the same directory where original mesh was saved.
If originally you saved your mesh as mesh_1.obj, after the above operation it will create mesh_1.obj.mtl and mesh_1.png. These are the three files needed to view textured mesh on any “.obj” file viewing software like Blender or autodesk etc.

References:

npm 安装软件包出错

rm -rf node_modules package-lock.json
npm audit fix --force
npm i --package-lock-only

iPhone 本地网络禁用导致无法传输文件

设置 -> 隐私 -> 本地网络

Use Touch ID for sudo on Mac

# Open the sudo utility
sudo vi /etc/pam.d/sudo

# Add the following as the first line
auth sufficient pam_tid.so

RViz 无法加载自定义插件

Could not load panel in rviz – PluginlibFactory: The plugin for class …

Solution:

You can put cpp and header files for your rviz related plugin together in one folder
or use the technique stated above (link both source and header to your created library)

Gradle

Gradle实战

tf2 convert transform to msg

Use ffmpeg compress media file with GPU acceleration

ffmpeg -i input.mp4 -r 20 -s vga -b:v 1.5M -c:v h264_videotoolbox output.mp4

If this fails your Python may not be configured for Tk

brew install python-tk@3.9

修改编译器

Error info: error: argument to '-V' is missing (expected 1 value)

cmake .. -DCMAKE_C_COMPILER='/usr/local/bin/x86_64-apple-darwin20-gcc-11.1.0'

修改安装路径

cmake .. -DCMAKE_INSTALL_PREFIX=/usr

Eigen/Core: No such file or directory

sudo ln -s /usr/include/eigen3/Eigen /usr/include/Eigen

Use `sed` on macOS

# Linux
$ sed -i "s/old/new/g" /path/to/file
# macOS
$ sed -i "" "s/old/new/g" /path/to/file

Use backward.hpp to Debug

#include <backward.hpp>
namespace backward {
  backward::SignalHandling sh;
}

set(CMAKE_BUILD_TYPE "Release")
set(CMAKE_CXX_FLAGS "-std=c++11")
set(CMAKE_CXX_FLAGS_RELEASE "-O3 -Wall -g")

Surge 配置方法

[Proxy]
DIRECT = direct
CN1-HK = custom, HOST, PORT, ENCODE, PASSWORD, http://example.com/
EXT-HK = custom, ......

[Proxy Group]
Proxy = select, CN1-HK, EXT-HK, DIRECT

Eigen 低版本导致编译失败

尽可能用新版本 Eigen

ROS 包生成 deb 安装文件

install(TARGETS receiver sender
  ARCHIVE DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
  LIBRARY DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
  RUNTIME DESTINATION ${CATKIN_GLOBAL_BIN_DESTINATION}
)

Issues: 安装后运行提示无法在 /opt/ros/melodic/share/XXX 路径下找到可执行节点

Solution: 修改 CATKIN_GLOBAL_BIN_DESTINATION 为 CATKIN_PACKAGE_BIN_DESTINATION

Qt Creator Setting Up a CMake Project

Setting Up a CMake Project

ROS 工作空间管理

source ws/devel/setup.bash --extend
echo $ROS_PACKAGE_PATH

Ubuntu 安装 GCC-10/G++-10

sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt-get install gcc-10 g++-10
sudo update-alternatives --remove-all gcc
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-5 90 --slave /usr/bin/g++ g++ /usr/bin/g++-5

Installing newer GCC versions in Ubuntu

优化/最优控制资料

代码优化资料

6.172 Performance Engineering of Software Systems

macOS (Big Sur) 源码编译 ROS 2 (foxy)

colcon build --symlink-install --packages-skip-by-dep python_qt_binding --packages-ignore turtlesim rviz2 rviz_visual_testing_framework rviz_default_plugins rviz_common

编译失败的包

turtlesim
rviz_common
rviz2
rviz_visual_testing_framework
rviz_default_plugins

原因：qt5 与 qt6 冲突

解决方法：删除 qt(v6)

brew uninstall qt

重新编译

colcon build --symlink-install --packages-skip-by-dep python_qt_binding
colcon build --symlink-install --packages-ignore rqt_gui_cpp qt_gui_cpp

Note: 部分包需要修改 CMakeLists.txt 以支持 C++17 才能通过编译

set(CMAKE_CXX_STANDARD 17)

加载环境

source ~/ros2_foxy/install/setup.sh

References:

Eigen 四元数或旋转矩阵转欧拉角出错

转换规则

If the rotation we converting from is an EulerAngles, angles ranges are undefined.
otherwise, alpha and gamma angles will be in the range [-PI, PI]. As for Beta angle:
- If the system is Tait-Bryan, the beta angle will be in the range [-PI/2, PI/2].
- otherwise:
  - If the beta axis is positive, the beta angle will be in the range [0, PI]
  - If the beta axis is negative, the beta angle will be in the range [-PI, 0]
Eigen::EulerAngles< _Scalar, _System > Class Template Reference
Euler angles
Bug 1301 - The second angle returned from eulerAngles does not have range (-PI/2, PI/2]

样条曲线

spline function是一类分段（片）光滑、并且在各段交接处也有一定光滑性的函数。简称样条。样条一词来源于工程绘图人员为了将一些指定点连接成一条光顺曲线所使用的工具，即富有弹性的细木条或薄钢条。由这样的样条形成的曲线在连接点处具有连续的坡度与曲率。分段低次多项式、在分段处具有一定光滑性的函数插值就是模拟以上原理发展起来的，它克服了高次多项式插值可能出现的振荡现象，具有较好的数值稳定性和收敛性，由这种插值过程产生的函数就是多项式样条函数。

样条函数

Understanding when not to std::move in C++

稀疏矩阵存储

ROS Server Parameters vs Dynamic Reconfigure?

Server Parameters vs Dynamic Reconfigure?

惯性张量的一个必要条件

The PRINCIPAL moments of inertia for that body about Bcm are:
[Imin = 0.0004078925; Imedium = 0.001790823; Imax = 0.002295285]
Real physical bodies require the "triangle-inequality" Imax <= Imin + Imed.

SpatialInertia::IsPhysicallyValid() fails for reasonable spatial inertia #16058

有问题的惯性张量来自 bullet3 提供的例子

  <inertial>
    <mass value="0.634"/>
    <origin xyz="0.0 0.016 -0.02"/>
    <inertia ixx="0.001983" ixy="0.000245" ixz="0.000013" iyy="0.002103" iyz="0.0000015" izz="0.000408"/>
  </inertial>

Drake 开发进度严谨而高效，为 TRI 工作人员点赞👍只是经常报一些奇怪的错

DDS

DDS与FastRTPS

一个奇怪的错误

costmap_2d 包删除 ObservationBuffer 对应头文件和源文件，编译通过，但是运行出错

Undefined symbol error when using tf2_ros::BufferInterface::transform

ROS 重映射方法

ROS 重映射功能支持 topic 和 tf 树节点

<node pkg="tf" type="tf_remap" name="tf_remapper" output="screen">
  <rosparam param="mappings">
    [{old: depth_camera, new: /camera_rgb_optical_frame},{old: thermal_camera, new: /camera_optris_frame}]
  </rosparam>
</node>

<node pkg="rosbag" type="play" name="player" args="--clock $(arg bag_dir)/$(arg file)">
  <remap from="tf" to="tf_old" />
</node>

需要注意，当需要重映射 nodelet 内部发布的 tf 话题时，需要在 nodelet 的 manager 节点启动时添加 remap 参数。

实现原理

#!/usr/bin/env python
# Software License Agreement (BSD License)
#
# Copyright (c) 2008, Willow Garage, Inc.
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
#  * Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
#  * Redistributions in binary form must reproduce the above
#    copyright notice, this list of conditions and the following
#    disclaimer in the documentation and/or other materials provided
#    with the distribution.
#  * Neither the name of Willow Garage, Inc. nor the names of its
#    contributors may be used to endorse or promote products derived
#    from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
#


## remap a tf topic

from __future__ import print_function

import rospy
from tf.msg import tfMessage

class TfRemapper:
    def __init__(self):
        self.pub = rospy.Publisher('/tf', tfMessage, queue_size=1)
        mappings = rospy.get_param('~mappings', [])
        self.mappings = {}

        for i in mappings:
            if "old" in i and "new" in i:
                self.mappings[i["old"]] = i["new"]

        print("Applying the following mappings to incoming tf frame ids", self.mappings)
        rospy.Subscriber("/tf_old", tfMessage, self.callback)

    def callback(self, tf_msg):
        for transform in tf_msg.transforms:
            if transform.header.frame_id in self.mappings:
                transform.header.frame_id = self.mappings[transform.header.frame_id]
            if transform.child_frame_id  in self.mappings:
                transform.child_frame_id = self.mappings[transform.child_frame_id]

        self.pub.publish(tf_msg)

def remap_tf():
    pub.publish(Empty())


if __name__ == '__main__':
    rospy.init_node('tf_remapper')
    tfr = TfRemapper()
    rospy.spin()

References

TF 原理

ROS1/2 相关学习资料

ROS 日志配置 log4j

案例

log4j.logger.ros.log_test=INFO,rosout_a                         # log_test是package名
log4j.appender.rosout_a=org.apache.log4j.RollingFileAppender    # 输出到文件，超过大小后自动创建下一个
log4j.appender.rosout_a.Threshold=INFO                          # 最低级别是INFO
log4j.appender.rosout_a.Append=true                             # 追加模式
log4j.appender.rosout_a.MaxFileSize=100KB                       # 每个日志文件的大小
log4j.appender.rosout_a.MaxBackupIndex=10                       # 最多产生多少日志文件，默认2个
log4j.appender.rosout_a.File=/home/hlhp/output.txt              # 输出文件，可结合环境变量${ROSOUT_LOG_PATH}
log4j.appender.rosout_a.layout=org.apache.log4j.PatternLayout   # 常用PatternLayout
log4j.appender.rosout_a.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss SSS} %m%n  # 输出格式

References

点云格式转换 XYZ -> XYZRGB

PointCloud<PointXYZ> cloud_xyz;
// [...]
PointCloud<PointXYZRGB> cloud_xyzrgb;
copyPointCloud(cloud_xyz, cloud_xyzrgb);

How to convert between different point cloud types using PCL?

ldd(Linux) 可视化版本 libtree

libtree

依赖库

Note: Use otool -L libfile on macOS.

What does if name == “main”: do?

What does if name == “main”: do?

拥抱 tf2_ros 舍弃 tf

tf 可能会导致程序异常

<node pkg="tf" type="static_transform_publisher" name="t265_to_d400" args="-0.009375589 0.015890727 0.028273059 0 0 0 /$(arg tf_prefix_camera1)_link /$(arg tf_prefix_camera2)_link 100"/>

建议使用 tf2_ros

<node pkg="tf2_ros" type="static_transform_publisher" name="t265_to_d400" args="-0.009375589 0.015890727 0.028273059 0 0 0 /$(arg tf_prefix_camera1)_link /$(arg tf_prefix_camera2)_link"/>

正确的流程开发

如何引导程序员新人按正确的流程开发?

用GitHub或类似的现代平台
平台上设置禁止直接push到主干，所有的修改必须fork后走Pull Request
启用CI(持续集成)，提PR时平台自动执行CI步骤，失败的不能被合并(不准开任何后⻔)
CI加入linter，确保代码规范;所有代码规范必须要可由linter检测，代码规范/linter配置规则也要针对实践中发现的问题不断补充细化和更新
CI加入单元测试，代码的测试覆盖率至少60%以上，核心模块测试覆盖率必须90%以上；所有发现的bug必须由造成bug的人负责补上单元测试
每个PR强制要求改动代码行数小于100行，新人要求小于60行，以利code review
每个PR在CI通过后必须有其他人进行过code review并approve，否则不能被merge，新人的代码必须至少有两人review和approve(比如新人的mentor和相关代码文件或目录的owner)
针对每个PR自动部署一份到测试环境，方便自测或提供给测试团队进行必要的测试
每2周检查近期bug，总结经验教训，特别是重复犯的错误一定要建立机制去防范

C++ 调试经验

重视现代编译器（gcc/g++ 10）输出的提示或警告内容，编译器能检查出一些简单的错误。有次花了3天时间才找到的BUG，其实编译器早早提示了需要 return *this;
用 GDB/Valgrind 排查

FOC 电机驱动算法

深入浅出讲解FOC算法与SVPWM技术

FOC 驱动器 vs 无刷电调

无刷直流电机（BLDC）vs 永磁同步电机（PMSM）

In simple terms, a BLDC motor has trapezoidal back-emf, whereas a PMSM has sinusoidal back-emf.
A BLDC motor works well with stepped input DC voltage, whereas a PMSM works well with purely sinusoidal voltage
PMSM has reduced torque ripple and current-ripple than BLDC motors.
BLDC motors have concentric windings whereas PMSM has distributed winding.
PMSMs are expensive, and highly efficienct. Suitable for high-power and high-efficiency applications.
BLDC motors are cost-effective. Suitable for low-power and low-cost applications.
Harmonic content is very high the stator current of BLDC motor due to its quazi-rectangular shape, whereas the stator current distortion in a PMSM is very less as it has a sinusoidal shape.

BLDC 反电动势接近梯形波，所以依然是采用方波驱动；PMSM 反电动势被设计为正弦波（利用 SVPWM）

内存对齐

EIGEN_MAKE_ALIGNED_OPERATOR_NEW
-march=native
SSE/AVX
从Eigen向量化谈内存对齐
Structures Having Eigen Members

深度相机清单

A Comprehensive List of 3D Sensors

Qt 经验

Qt的signal/slot是为了解决对象间通信问题，同时避免共享指针造成的内存野指针和对象生命周期问题

Window::Window()
{
    QPushButton *b = new QPushButton(this);
    connect(b, SIGNAL(clicked()), SLOT(on_button_clicked()));
}

Window::on_button_clicked()
{
    QPushButton *b = qobject_cast<QPushButton*>(sender());
    b->setText("clicked!");
}

YouTube tools

Roslaunch 使用方法

Roslaunch 节点调试

... launch-prefix="xterm -e gdb --args" ...
... launch-prefix="gdb -ex run --args" ...

Inside Macintosh Series - original version 下载地址

Software optimization resources

代码优化指南

Spot 机器人官方 PDF 文档 & Videos

图像与视频编辑工具

Phenomenological Introduction to PID controllers PID 原理

V. Hunter Adams, Lecturer of Electrical Engineering, Cornell University

视频搬运及其字幕下载根工具

5s
DownSub

中国大学MOOC—《机器人操作系统入门》课程讲义

Ubuntu Install librealsense2 from source

catkin install

Building and using catkin packages in a workspace

cd ~/catkin_ws
catkin_make install

用 CPack 生成 deb 安装包

修改 CMakeLists.txt 文件，添加

set(CPACK_PACKAGE_NAME "example")
set(CPACK_SET_DESTDIR ON)
set(CPACK_INSTALL_PREFIX "/home/vesoft/install")
set(CPACK_PACKAGE_VERSION "1.0.0")
set(CPACK_RPM_PACKAGE_GROUP "vesoft")
set(CPACK_PACKAGE_VENDOR "vesoft")
set(CPACK_RPM_PACKAGE_LICENSE "Apache 2.0 + Common Clause 1.0")
include(CPack)

注

cat install_manifest.txt | xargs echo sudo rm | sh

static_transform_publisher 角度顺序

static_transform_publisher x y z yaw pitch roll frame_id child_frame_id period_in_ms

static_transform_publisher x y z qx qy qz qw frame_id child_frame_id  period_in_ms

How can I catch a ctrl-c event?

#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>

void my_handler(int s){
           printf("Caught signal %d\n",s);
           exit(1); 

}

int main(int argc,char** argv)
{

   struct sigaction sigIntHandler;

   sigIntHandler.sa_handler = my_handler;
   sigemptyset(&sigIntHandler.sa_mask);
   sigIntHandler.sa_flags = 0;

   sigaction(SIGINT, &sigIntHandler, NULL);

   pause();

   return 0;    
}

Ouster 雷达时间同步

手眼标定 `AX=XB`

Precision Time Protocol

TODO

cv::Mat <-> Eigen::Matrix

void eigen2cv(const Eigen::Matrix<_Tp, _rows, _cols, _options, _maxRows, _maxCols>& src, Mat& dst)
void cv2eigen(const Mat& src, Eigen::Matrix<_Tp, _rows, _cols, _options, _maxRows, _maxCols>& dst)

Useful Tools & Links

ReadMe (export from Safari 20220505)

Solutions : Rethink Robotics https://support.rethinkrobotics.com/support/solutions

Differential Equations, Mechanics, and Computation https://ode-math.com/

ros-drivers/video_stream_opencv: A package to open video streams and publish them in ROS using the opencv videocapture mechanism https://github.com/ros-drivers/video_stream_opencv

camera_calibration - ROS Wiki https://wiki.ros.org/camera_calibration

ldconfig(8) - Linux man page https://linux.die.net/man/8/ldconfig

bernhardpg/collision-free-mixed-integer-planning-for-uavs: Collision-Free Mixed-Integer Planning for Quadrotors Using Convex Safe Regions https://github.com/bernhardpg/collision-free-mixed-integer-planning-for-uavs

python - how does cv2.VideoCapture() changes capture resolution? - Stack Overflow https://stackoverflow.com/questions/14011428/how-does-cv2-videocapture-changes-capture-resolution

OpenCV: Video I/O with OpenCV Overview https://docs.opencv.org/4.5.5/d0/da7/videoio_overview.html

dottantgal/ROS2_learning: A useful collection of CPP examples to learn ROS2 from zero https://github.com/dottantgal/ROS2_learning

Tutorial · jbeder/yaml-cpp Wiki https://github.com/jbeder/yaml-cpp/wiki/Tutorial

Drake Concepts - Drake Tutorial https://drake.guzhaoyuan.com/introduction/drake-concept

https://arxiv.org/pdf/1909.05700.pdf https://arxiv.org/pdf/1909.05700.pdf

sebastianstarke/AI4Animation: Bringing Characters to Life with Computer Brains in Unity https://github.com/sebastianstarke/AI4Animation

Humanoid Robot Animation | Udemy https://www.udemy.com/course/humanoid-robot-animation/

medalotte/sampling-based-planners: C++ implementation of RRT, RRT, and Informed-RRT using kd-tree for searching NN and NBHD nodes. Supports arbitrary dimensions and compiles as a shared library. https://github.com/medalotte/sampling-based-planners

ntnu-arl/gbplanner_ros: Graph-based Exploration Planner for Subterranean Environments https://github.com/ntnu-arl/gbplanner_ros

static members - cppreference.com https://en.cppreference.com/w/cpp/language/static

David-Haim/concurrencpp: Modern concurrency for C++. Tasks, executors, timers and C++20 coroutines to rule them all https://github.com/David-Haim/concurrencpp

MLNLP-World/Paper-Writing-Tips: Paper Writing Tips https://github.com/MLNLP-World/Paper-Writing-Tips

Visualizing quaternions, an explorable video series https://eater.net/quaternions

geekan/HowToLiveLonger: 程序员延寿指南 | A programmer’s guide to live longer https://github.com/geekan/HowToLiveLonger

miloyip/json-tutorial: 从零开始的 JSON 库教程 https://github.com/miloyip/json-tutorial

InteractiveComputerGraphics/PositionBasedDynamics: PositionBasedDynamics is a library for the physically-based simulation of rigid bodies, deformable solids and fluids. https://github.com/InteractiveComputerGraphics/PositionBasedDynamics

CppCon 2018: Bjarne Stroustrup “Concepts: The Future of Generic Programming (the future is here)” - YouTube https://www.youtube.com/watch?v=HddFGPTAmtU

CppCon 2018: Michael Gopshtein “CUDA Kernels with C++” - YouTube https://www.youtube.com/watch?v=HIJTRrm9nzY

Drake: MultibodyPlant< T > Class Template Reference https://drake.mit.edu/doxygen_cxx/classdrake_1_1multibody_1_1_multibody_plant.html#a029b22a36d5c6ee85247b9c1cfe84c6b

parallel101/course: 高性能并行编程与优化 - 课件 https://github.com/parallel101/course

相关问题 · Issue #1 · ShuoYangRobotics/A1-QP-MPC-Controller https://github.com/ShuoYangRobotics/A1-QP-MPC-Controller

Dual quaternion - Wikipedia https://en.wikipedia.org/wiki/Dual_quaternion

udev - Assign webcam to a specific /dev/video# - Ask Ubuntu https://askubuntu.com/questions/715333/assign-webcam-to-a-specific-dev-video

MatthewPeterKelly/OptimTraj: A trajectory optimization library for Matlab https://github.com/MatthewPeterKelly/OptimTraj

How to Write a Git Commit Message https://cbea.ms/git-commit/

pdn odn on Behance https://www.behance.net/12f6

hengli/camodocal: CamOdoCal: Automatic Intrinsic and Extrinsic Calibration of a Rig with Multiple Generic Cameras and Odometry https://github.com/hengli/camodocal

narutojxl/direct_lidar_odometry_noted https://github.com/narutojxl/direct_lidar_odometry_noted

Quake Source Code Review https://fabiensanglard.net/quakeSource/

Drake: MathematicalProgram Class Reference https://drake.mit.edu/doxygen_cxx/classdrake_1_1solvers_1_1_mathematical_program.html

Ch. 22 - Multi-Body Dynamics http://underactuated.mit.edu/multibody.html#section1

C++语言的单元测试与代码覆盖率 https://paul.pub/gtest-and-coverage/

qmake convert to cmake

#!/bin/sh

QTVERSION=5

FILES="$(find . -name '*.cpp' -o -name '*.qrc' -o -name '*.ui' | sed -e 's,\.\/,  ,')"
if [ -z "$FILES" ]; then
  echo "No cpp files found in the current directory"
  exit 1
fi
PROJECTNAME=$(basename "$PWD" | sed -e 's/ /_/g')
TARGET="$PROJECTNAME"

if [ "$QTVERSION" != "none" ]; then
  QT=Qt$QTVERSION
  QTLIBS="Core Gui"
  QTTARGETS="$QT::Core $QT::Gui"
  if [ -n "$(grep QApplication *.cpp)" ]; then
    QTLIBS="$QTLIBS Widgets"
    QTTARGETS="$QTTARGETS $QT::Widgets"
    AUTOUIC="set(CMAKE_AUTOUIC TRUE)"
  fi
fi

cat >CMakeLists.txt <<EOF
cmake_minimum_required(VERSION 3.9)
project($PROJECTNAME)
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_INCLUDE_CURRENT_DIR ON)
EOF

if [ "$QTVERSION" != "none" ]; then
  cat >>CMakeLists.txt <<EOF
find_package($QT CONFIG REQUIRED COMPONENTS $QTLIBS)
set(CMAKE_AUTOMOC TRUE)
set(CMAKE_AUTORCC TRUE)
$AUTOUIC
EOF
fi

cat >>CMakeLists.txt <<EOF
add_executable($PROJECTNAME
$FILES
)
EOF

if [ "$QTVERSION" != "none" ]; then
  cat >>CMakeLists.txt <<EOF
target_link_libraries($PROJECTNAME $QTTARGETS)
EOF
fi

Reference: https://github.com/KDAB/KDToolBox/tree/master/qt/cmake-project

路径规划算法评价指标

成功率
距离终点的距离
计算时间
与最短路径的偏差
路径长度
搜索空间
最大内存占用
距离障碍物的平均距离
轨迹平滑程度

定位算法评价指标

absolute pose error
relative pose error

References

PathBench
Python package for the evaluation of odometry and SLAM
[Metrics for System Assessment Autonomous Navigation, Part 6](https://www.youtube.com/watch?v=k3bzouQNIwE)

Notes for Drake

convexity of the quadratic cost

GoogleTest for CMake

cmake_minimum_required(VERSION 3.14)
project(my_project)

# GoogleTest requires at least C++11
set(CMAKE_CXX_STANDARD 11)

include(FetchContent)
FetchContent_Declare(
  googletest
  URL https://github.com/google/googletest/archive/609281088cfefc76f9d0ce82e1ff6c30cc3591e5.zip
)
# For Windows: Prevent overriding the parent project's compiler/linker settings
set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
FetchContent_MakeAvailable(googletest)

Ref:

自动微分 Automatic Differentiation = AD

Dual Numbers a+bϵ (s.t. ϵ^2=0)

Ref:

点云编辑工具 Point Clouds Editor

How to make uninstall

sudo xargs rm < install_manifest.txt

Solution for `fatal error: 'opencv2/highgui.hpp' file not found`

ln -s /usr/local/include/opencv4/opencv2/ /usr/local/include/opencv2

C++ 代码格式化

find DIRECTORY -iname '*.h' -o -iname '*.hh' -o -iname '*.hpp' -o -iname '*.c' -o -iname '*.cc' -o -iname '*.cpp' | xargs clang-format -style=google -i

Drake 优加入梯度信息

Ref: Provide custom gradient to drake::MathematicalProgram

from pydrake.all import AutoDiffXd, MathematicalProgram, Solve

prog = MathematicalProgram()
x = prog.NewContinuousVariables(1, 'x')

def cost(x):
    return (x[0]-1.)*(x[0]-1.)

def constraint(x):
    if isinstance(x[0], AutoDiffXd):
        y = AutoDiffXd(2*x[0].value(), 2*x[0].derivatives())
        return [y]
    return 2*x

cost_binding = prog.AddCost(cost, vars=x)
constraint_binding = prog.AddConstraint(
    constraint, lb=[0.], ub=[2.], vars=x)
result = Solve(prog)

NumPy(Python) == Eigen(C++)

Ref:

djvu2pdf

brew install djvu2pdf
djvu2pdf INPUT.djvu OUTPUT.pdf

Orchestration vs. Choreography

C++为什么允许给临时对象赋值

force1+force2=net;
(force1+force2).operator=(net);

例子

#include <string>

struct A {
  int n;
  std::string s1;
  A() = default;
  A(A const&) = default;
  A& operator=(const A& p) = delete;
};

int main() {
  A a;
  A() = a;  // error: overload resolution selected deleted operator '='
}

An Introduction to real-time Linux

https://www.youtube.com/watch?v=cZs6HQdbzX4

Point-to-Point vs Contouring

What’s the difference between contouring and point-to-point motion?

永磁无刷直流电机

反电动势波形为方波的永磁同步电机称为永磁无刷直流电机

双足机器人资料

协程

函数其实只是没有挂起点的协程

一款超好用的画图工具 tldraw

tldraw

Linux 打印自启动服务

$ sudo systemctl --all list-unit-files --type=service
# OR
$ ls /lib/systemd/system/*.service /etc/systemd/system/*.service

Ref: Command to list services that start on startup?

MacBook 开启指纹代替 `sudo`

$ cd /etc/pam.d
$ sudo vim ./sudo
# Add the following below the first line
auth sufficient pam_tid.so

Ref: Quick Tip: Enable Touch ID for sudo

Python Issue `ApplePersistenceIgnoreState: Existing state will not be touched.`

Solution

$ defaults write org.python.python ApplePersistenceIgnoreState NO
# Reset
# defaults write org.python.python ApplePersistenceIgnoreState YES

Apollo-Platform vs ROS

ROS Decentralization Feature
High Efficient Communication based on Shared Memory Transport Feature
Native Support with Protobuf Feature

Cite: https://github.com/ApolloAuto/apollo-platform/blob/master/ros/docs/design

多 ROS1 Master 通信配置

multimaster_fkie

The multimaster_fkie solution only supports topics and services, however actions are implicitly supported because they are build on top of 5 topics.

MoveIt Architecture

树莓派 Serial to USB, no ttyUSB0

Personally I managed to have ttyUSB appear through $raspi-config. You just have to go to Interfaces Settings and say you want the serial port activated. Finally, $sudo reboot.

Cite: https://raspberrypi.stackexchange.com/questions/91181/serial-to-usb-no-ttyusb0

Drake 二进制安装方法

sudo tar -xvzf drake-20220114-mac.tar.gz -C /opt

MuJoCo 编译问题解决

Issues

ld64.lld: error: unknown argument '--gc-sections'

Solution

<!-- Change -->
-Wl,--gc-sections
<!-- to -->
-Wl,-dead_strip

计算 SHA256

$ openssl dgst -sha256 <file>
# or
$ shasum -a 256 <file>

LaTeX 中文模版

\documentclass{ctexart}
\begin{document}
\tableofcontents

\begin{abstract}
这是简介及摘要。
\end{abstract}

\section{前言}

\section{关于数学部分}
数学、中英文皆可以混排。You can intersperse math, Chinese and English (Latin script) without adding extra environments.

這是繁體中文。
\end{document}

iperf 带宽测试

# Server
$ iperf -s

# Client
$ iperf -c SERVER_IP

BIOS + recovery mode + nouveau

TECH TALK: ALL ABOUT SPOT’S API

https://www.bostondynamics.com/resources/webinar/API-tech-talk

Layerd API

Base
1. gRPC
2. SDK
Movement
1. State
2. Commands
Autonomy
1. GraphNav
2. Missions(BT)
Data
1. Data Acquisition
2. Network Compute Bridge

Manipulation API

Ubuntu 16.04 install gcc9

Download sources codes: https://link.zhihu.com/?target=http%3A//ftp.gnu.org/gnu/gcc/gcc-9.1.0/gcc-9.1.0.tar.gz
Unzip and $ cd gcc-9.1.0
Download deps: $ ./contrib/download_prerequisites
$ mkdir build;cd build;../configure -enable-checking=release -enable-languages=c,c++ -disable-multilib
$ make && make install

ROS bugs’ solution

sudo apt update
sudo apt upgrade

COSTMAP_2D 图像坐标系 frames

Origin: left-down corner
X_axis: right→
Y_axis: up↑

Ref: GridMap(ETH)

用命令行实现图像拼接

convert 1.png 2.png 3.png -append 123.png

文件加密压缩

zip -e name.zip raw_file

布料仿真流水线

In computer graphics, building your own wheel can often be unevitable. But what fears most is that sometimes you don’t even have recipe for the wheel you want to build. There are lots of great paper describing their methods, but many of the implementation details are left out or scattered across the internet.

CollideSDF(); // Collide particles with Signed Distance Fields (Q1)
for (int substep = 0; substep < numSubsteps; substep++) // Reference: [Small steps in physics simulation, 2019]
{
    PredictPositions();           // Predict particle positions
    FindNeighborsBySpatialHash(); // Use spatial hashing to find particle neighbors
    
    // Handle Collisions
    CollideParticles();           // Collide particles with neighboring particles
    CollideSDF();                 // Collide particles with Signed Distance Fields

    // Solve constraints
    for (int iteration = 0; iteration < numIterations; iteration++)
    {
        SolveStretch();           // Stretch constraint keeps the distance between two particles
        SolveAttachment();        // Attachment constraint keeps the distance between a particle and a 3D position
        // SolveBending();        // Bending constraints doesn't work well on GPU (Q2)
        ApplyDeltas();            // Apply position deltas accumulated in previous constraint solving (Q3)
    }
    
    Finalize();                   // Update velocities and positions
}
ComputeNormals();                 // Compute vertex normals for rendering

统计代码量

cloc file_or_directory

Markdown to PDF using pandoc & rmarkdown

Setting

---
geometry: margin=2cm
output: pdf_document
CJKmainfont: MiSans
colorlinks: true
linkcolor: blue
urlcolor: red
toccolor: gray
title: 机器人感知规划相关资料
author: matheecs
---

Usages

pandoc SLAM_Perceptioin_Planning.md -o SLAM_Perceptioin_Planning.pdf --pdf-engine=xelatex

Pandoc Debug

Error at "user-guide-cn.tex" (line 901, column 1):
unexpected \end
\end{document}
^

分段排查错误发现原因是多了一个 { 大括号

ThinkPad 合盖不休眠设置

sudo gedit /etc/systemd/logind.conf

Uncomment the line

#HandleLidSwitch=suspend

Change the value to:

HandleLidSwitch=ignore

restart service

systemctl restart systemd-logind.service

Ref: How to Change Lid Close Action in Ubuntu 18.04 LTS

Dot 文件转换

dot -Tpdf art_planner.dot -o art_planner.pdf

Use `$tldr` instead of `$man`

sudo apt install tldr
tldr -u

Ubuntu 22.04 ARM64 `/etc/apt/sources.list`

deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ jammy main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ jammy-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ jammy-backports main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ jammy-security main restricted universe multiverse

SSH 远程登录开启可视化界面

export DISPLAY=:0
ssh -Y remote_host
xedit

OMPL link error `library not found for -lode`

Solution

find_package(OMPL REQUIRED)
add_executable(ompl_test ompl_test.cc)
target_include_directories(ompl_test PRIVATE ${OMPL_INCLUDE_DIRS})
target_link_directories(ompl_test PRIVATE ${OMPL_LIBRARY_DIRS})
target_link_libraries(ompl_test PRIVATE ${OMPL_LIBRARIES})

Ref: Fix linking issues for ODE on macOS

用 tcpNoDelay 实现ROS低延时通信

Ref : What are the differences between the different TransportHints?

用 `ccache` 加速编译

brew install ccache
export PATH=/opt/homebrew/opt/ccache/libexec:$PATH

Ref: Ccache

Use `sudo -E` to preserve their existing environment variables

sudo -E rosdep init

Ref: Add support for proxys

rosdep 换源

sudo rosdep init
rosdep update

改为执行

# 手动模拟 rosdep init
sudo mkdir -p /etc/ros/rosdep/sources.list.d/
sudo curl -o /etc/ros/rosdep/sources.list.d/20-default.list https://mirrors.tuna.tsinghua.edu.cn/github-raw/ros/rosdistro/master/rosdep/sources.list.d/20-default.list
# 为 rosdep update 换源
export ROSDISTRO_INDEX_URL=https://mirrors.tuna.tsinghua.edu.cn/rosdistro/index-v4.yaml
rosdep update

# 每次 rosdep update 之前，均需要增加该环境变量
# 为了持久化该设定，可以将其写入 .bashrc 中，例如
echo 'export ROSDISTRO_INDEX_URL=https://mirrors.tuna.tsinghua.edu.cn/rosdistro/index-v4.yaml' >> ~/.bashrc

Ref: rosdistro 镜像使用帮助

Linux Wi-Fi 信号强度测量工具

sudo apt-get install wavemon
wavemon
# or
iwconfig

USE -lpthread instead of -lpthreads

git diff

git diff --patch > mypatch.patch
git apply mypatch.patch

rqt_launchtree

Cite: rqt_launchtree

Entity Component System

Operation Costs in CPU Clock Cycles

Cite: Infographics: Operation Costs in CPU Clock Cycles

CMake: Finding Qt 5 the “Right Way”

set(QT5_ROOT_PATH CACHE PATH "Qt5 root directory (i.e. where the 'bin' folder lies)")
if (QT5_ROOT_PATH)
    list(APPEND CMAKE_PREFIX_PATH ${QT5_ROOT_PATH})
endif ()

Cite: CMake: Finding Qt 5 the “Right Way”

批量转图像格式

for f in *.HEIC; do heif-convert -q 100 $f $f.jpg; done

Optional

# install imagemagick
brew install imagemagick

# convert a single image
magick convert foo.HEIC foo.jpg

# bulk convert multiple images
magick mogrify -monitor -format jpg *.HEIC

Cite: How to convert a HEIF/HEIC image to JPEG in macOS?

PCA vs Moment of Inertia

主成分可以在科学的各个领域找到。例如，有一个与物理学相类似的例子。如果把三维数据点看作是一个刚体的质量点，那么特征值对应于惯性的主矩，主成分对应于身体的主轴。

Ref:

搜索重复文件

View Image in CLI

brew install viu

A code-searching tool

brew install the_silver_searcher

STM32CubeIDE 安装报错(文件损坏)

xattr -c /Applications/STM32CubeIDE.app

LCM 局域网通信

/* multicast time-to-live = 0 or 1 */
lcm::LCM lcm("udpm://239.255.76.67:7667?ttl=1");

LCM =

Type Specification
Marshalling = Serialization (encode/decode)
Communication = UDP Multicast
Tools = lcm-spy
Note: Unplug the extra network cable (拔掉多余的网线)

Cite: UDP Multicast Setup

Header files for x86 SIMD intrinsics

<mmintrin.h>  MMX
<xmmintrin.h> SSE
<emmintrin.h> SSE2
<pmmintrin.h> SSE3
<tmmintrin.h> SSSE3
<smmintrin.h> SSE4.1
<nmmintrin.h> SSE4.2
<ammintrin.h> SSE4A
<wmmintrin.h> AES
<immintrin.h> AVX, AVX2, FMA

循环执行程序

while :; do ./send-message; sleep 1; done

Find Custom Python using CMake

set(Python3_FIND_FRAMEWORK NEVER)

Do not use `include_directories` in CMake

Use

target_include_directories

Cite 彭于斌

macOS architecture

Cite Mac OS X Internals

Mesh file format convert using MeshLab

for file in *.STL
do
  meshlabserver -i $file -o ${file%.*}.obj -m vn
done

C++ IDE using VS Code & clangd & Ccache

set(CMAKE_EXPORT_COMPILE_COMMANDS ON)

Screen record using OBS Studio

OBS Studio

Video format convert using FFmpeg

ffmpeg -ss 30 -t 3 -i input.mkv -vf "fps=10,scale=640:-1:flags=lanczos,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse" -loop 0 output.gif

# or

ffmpeg -ss 00:01:00 -to 00:02:00 -i input.mp4 -c copy output.mp4

How to keep environment variables when using `sudo`

man sudo
sudo -E todooooooooo

Use ROS packages via CMake

ros1_external_use

CMake target_link_libraries Interface Dependencies

If you are creating a shared library and your source cpp files #include the headers of another library (Say, QtNetwork for example), but your header files don’t include QtNetwork headers, then QtNetwork is a PRIVATE dependency.

If your source files and your headers include the headers of another library, then it is a PUBLIC dependency.

If your header files other than your source files include the headers of another library, then it is an INTERFACE dependency.

Cite:

GCC -> Clang

Template instantiation of templated class constructor

用 `ffmpeg` 添加字幕

ffmpeg -i nmpc_wbc_with_raibert.mp4 -vf "subtitles=sub.srt:force_style='Fontsize=24'" -c:a copy mysubtitledmovie.mp4

C++ Thread Synchronization

SVG to PDF using inkscape

inkscape -D image.svg  -o image.pdf --export-latex

OCR for PDF files using OCRmyPDF

brew install ocrmypdf

ocrmypdf -l eng --deskew --jobs 4 --force-ocr input.pdf output.pdf

Ubuntu install latest CMake

Kitware APT Repository

cmake -Bbuild -GNinja -DCMAKE_BUILD_TYPE=Release -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -DCMAKE_COLOR_DIAGNOSTICS=ON

ROS workspace setup for VSCode IDE

catkin_make -DCMAKE_BUILD_TYPE=Release -DCMAKE_EXPORT_COMPILE_COMMANDS=Yes

Cite: https://github.com/catkin/catkin_tools/issues/551

catkin build -DCMAKE_EXPORT_COMPILE_COMMANDS=1

with follow scripts

#!/bin/sh

cd `catkin locate --workspace $(pwd)`

concatenated="build/compile_commands.json"

echo "[" > $concatenated

first=1
for d in build/*
do
    f="$d/compile_commands.json"

    if test -f "$f"; then
        if [ $first -eq 0 ]; then
            echo "," >> $concatenated
        fi

        cat $f | sed '1d;$d' >> $concatenated
    fi

    first=0
done

echo "]" >> $concatenated

Convert Mesh files

#!/bin/sh
for i in `find . -name '*.STL'`; do
    meshlabserver -i $i -o `pwd`/$(echo `basename $i` | sed 's|.STL$|.obj|')
done

A bug funded by Clang

bug

fatal error: qualified reference to 'MultidimensionalPenalty' is a constructor name rather than a type

template <>
MultidimensionalPenalty::MultidimensionalPenalty<augmented::AugmentedPenaltyBase>(
    std::vector<std::unique_ptr<augmented::AugmentedPenaltyBase>> penaltyPtrArray)
    : penaltyPtrArray_(std::move(penaltyPtrArray)) {
  if (penaltyPtrArray_.empty()) {
    throw std::runtime_error("[MultidimensionalPenalty::MultidimensionalPenalty] The penalty array cannot be empty!");
  }
}

fix

template <>
MultidimensionalPenalty::MultidimensionalPenalty(
    std::vector<std::unique_ptr<augmented::AugmentedPenaltyBase>> penaltyPtrArray)
    : penaltyPtrArray_(std::move(penaltyPtrArray)) {
  if (penaltyPtrArray_.empty()) {
    throw std::runtime_error("[MultidimensionalPenalty::MultidimensionalPenalty] The penalty array cannot be empty!");
  }
}

Inertia Convention of SolidWorks

There are some CAD and CAE applications such as SolidWorks, Unigraphics NX/Siemens NX and MSC Adams that use an alternate convention for the products of inertia. According to this convention, the minus sign is removed from the product of inertia formulas and instead inserted in the inertia matrix.

cite: https://en.wikipedia.org/wiki/Moment_of_inertia

Enable Dark Mode in Chrome on Ubuntu

Type chrome://flags in the address bar;
Type “dark mode” in the search bar;
Select Enabled for Force Dark Mode for Web Contents.

Cite: How to Enable Dark Mode in Chrome on Ubuntu

Fix bug of ROS with PyQt?

Solution: use pip to uninstall PyQt5 and PyQt5-sip

C++20 Eigen Bug

error: return type ...::RCmpEQReturnType of selected 'operator==' function for rewritten '!=' comparison is not 'bool'

Solution: use C++17

Cite: Breaking change in C++20 or regression in clang-trunk/gcc-trunk when overloading equality comparison with non-Boolean return value?

Python to UML

# pip install pylint
pyreverse -o png <path_to_src>

Cite: How to Generate UML Diagrams from Python Source Code?

Teleoperation with the mouse

rosrun mouse_teleop mouse_teleop.py /mouse_vel:=/cmd_vel

Weixin for Linux

Cite: https://www.ubuntukylin.com/applications/106-cn.html

Pinyin for Chrome

Google Input Tools

fatal error: Eigen/Core: No such file or directory

sudo ln -s /usr/include/eigen3/Eigen /usr/include/Eigen

Docker: Proxy setup

Add file: ~/.docker/config.json

{
 "proxies":
 {
   "default":
   {
     "httpProxy": "http://192.168.1.12:3128",
     "httpsProxy": "http://192.168.1.12:3128",
     "noProxy": "*.test.example.com,.example2.com,127.0.0.0/8"
   }
 }
}

Cite: Configure Docker to use a proxy server

Docker: Networking using the host network

docker run --network host -it -v $PWD:"/github/workspace" qsim /bin/bash

Cite: Networking using the host network

Docker: 镜像加速器

Docker Desktop -> Perferences -> Docker Engine -> Add JSON

{
  "registry-mirrors": [
    "https://hub-mirror.c.163.com",
    "https://mirror.baidubce.com"
  ]
}

Ubuntu: Setup GCC and Ccache

sudo apt install gcc-8 g++-8 gcc-9 g++-9 gcc-10 g++-10
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-10 100 --slave /usr/bin/g++ g++ /usr/bin/g++-10 --slave /usr/bin/gcov gcov /usr/bin/gcov-10
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-9 90 --slave /usr/bin/g++ g++ /usr/bin/g++-9 --slave /usr/bin/gcov gcov /usr/bin/gcov-9
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-8 80 --slave /usr/bin/g++ g++ /usr/bin/g++-8 --slave /usr/bin/gcov gcov /usr/bin/gcov-8
sudo update-alternatives --config gcc

export PATH=/usr/lib/ccache:$PATH

$ ls -l /usr/lib/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 c++ -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 c89-gcc -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 c99-gcc -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 cc -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 g++ -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 g++-10 -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 g++-11 -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 g++-8 -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 g++-9 -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 gcc -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 gcc-10 -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 gcc-11 -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 gcc-8 -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 gcc-9 -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 x86_64-linux-gnu-g++ -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 x86_64-linux-gnu-g++-10 -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 x86_64-linux-gnu-g++-11 -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 x86_64-linux-gnu-g++-8 -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 x86_64-linux-gnu-g++-9 -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 x86_64-linux-gnu-gcc -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 x86_64-linux-gnu-gcc-10 -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 x86_64-linux-gnu-gcc-11 -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 x86_64-linux-gnu-gcc-8 -> ../../bin/ccache
lrwxrwxrwx   1 root root    16 3月  20 14:53 x86_64-linux-gnu-gcc-9 -> ../../bin/ccache

$ which gcc
/usr/lib/ccache/gcc

Cite:

Ubuntu: Install AppImageLauncher

sudo add-apt-repository ppa:appimagelauncher-team/stable
sudo apt-get update
sudo apt-get install appimagelauncher

Find pip package and import it into CMake

find_package(
  Python 3.8
  COMPONENTS Interpreter Development.Module
  REQUIRED)

# Detect the installed pybind11 package and import it into CMake
execute_process(
  COMMAND "${Python_EXECUTABLE}" -m pybind11 --cmakedir
  OUTPUT_STRIP_TRAILING_WHITESPACE
  OUTPUT_VARIABLE PYBIND11_DIR)
list(APPEND CMAKE_PREFIX_PATH "${PYBIND11_DIR}")
find_package(pybind11 REQUIRED)

Cite: Setting up a build system

C++ 静态检测

作者：吴咏炜链接：https://www.zhihu.com/question/452639015/answer/1814806992 编译器仍然是最“好”的检查工具。使用 GCC/Clang 时，我现在一般会开启 -Werror -Wfatal-errors -Wall -Wextra，可以不费任何力气发现很多的常见错误。使用超过一个编译器。比如，如果你日常使用 GCC 的话，考虑使用 Clang 来编译；反之亦然。一般而言，最常用的三个编译器中，Clang 对 C++ 标准的符合程度最高，但凡事不绝对，多用几个为好。LLVM 项目除了产出了 LLVM 虚拟机和 Clang 编译器，还有一大堆小工具可以用。我日常用 Clang-Format 来格式化代码，用 Clang-Tidy 来检查代码的合规性。注意这两个工具就不是随便用几个命令行选项了，而是应该使用配置文件来进行配置。Clang-Tidy 的选项还是相当复杂的，从代码风格的现代化，可读性，常见错误，是否满足《C++ 核心指南》里的条款，到是否满足某些特定行业的编码规范，虽然不是应有尽有，也是相当丰富了。哦，对了，作为 Clang 生态的额外奖励，如果你的编辑环境使用 Clangd 作为语言支持（如 Visual Studio Code 和 Vim 都支持），你在添加了 Clang-Tidy 配置文件之后，可以直接在编辑环境看到问题的加亮。这绝对是效率利器。

ThinkPad X1 update firmware

fwupdmgr refresh
fwupdmgr get-updates
fwupdmgr update

Print Eigen vector in spdlog & fmt

#include "spdlog/fmt/ostr.h" 

Cite: https://github.com/gabime/spdlog/issues/1638

Merge PDFs using `pdfunite`

pdfunite *.pdf out.pdf

Homebrew 源使用帮助

export HOMEBREW_BREW_GIT_REMOTE="https://mirrors.ustc.edu.cn/brew.git"
export HOMEBREW_CORE_GIT_REMOTE="https://mirrors.ustc.edu.cn/homebrew-core.git"
export HOMEBREW_BOTTLE_DOMAIN="https://mirrors.ustc.edu.cn/homebrew-bottles"
export HOMEBREW_API_DOMAIN="https://mirrors.ustc.edu.cn/homebrew-bottles/api"

Cite: https://mirrors.ustc.edu.cn/help/brew.git.html

ARM or x86? ISA Doesn’t Matter

Here in this article we’ll bring together research, comments from people who are very familiar with CPUs, and a bit of our in-house data to show why focusing on the ISA is a waste of time(1) and to start us off on our little adventure, let’s reference Anandtech’s interview of Jim Keller, an engineer who worked on several successful CPU designs including AMD’s Zen and Apple’s A4/A5. cite: https://chipsandcheese.com/2021/07/13/arm-or-x86-isa-doesnt-matter

Compare CPUs

Cite: https://nanoreview.net/en/cpu-compare

How to create a Minimal, Reproducible Example

MCVE = minimal, complete and verifiable example

cite: https://stackoverflow.com/help/minimal-reproducible-example

TO with PD

torque = damping + motor

Memory Alignment

Anna’s Archive

https://annas-archive.org

Mobile Phone Museum

https://www.mobilephonemuseum.com/catalogue

Use mold (A Modern faster Linker)

sudo apt install mold

# ld.lld: No such file or directory
sudo ln -s /usr/bin/ld.lld-16 /usr/bin/ld.lld

CMake support

add_link_options("-fuse-ld=mold")

Eigen: do not use the `auto` keywords

DO NOT use the auto keywords with Eigen’s expressions, unless you are 100% sure about what you are doing. In particular, do not use the auto keyword as a replacement for a Matrix<> type.

Cite:

Swapping the FN and CTRL keys on MacBook/ThinkPad

BIOS (ThinkPad)
Preferences > Keyboard > Keyboard Shortcuts… > Modifier Keys (MacBook)

Use cProfile & snakeviz

python -m cProfile -o demo.prof demo.py
snakeviz demo.prof

ncalls: Total number of calls to the function. If there are two numbers, that means the function recursed and the first is the total number of calls and the second is the number of primitive (non-recursive) calls.
tottime: Total time spent in the function, not including time spent in calls to sub-functions
percall: tottime divided by ncalls
cumtime: Cumulative time spent in this function and all sub-functions
percall: cumtime divided by ncalls
filename:lineno(function): File name and line number were the function is defined, and the function’s name

Git export zip file

git archive --format=zip --output /full/path/to/zipfile.zip master

How to destroy an object in C++?

Use smart pointers to create and delete your objects. The easiest one to use is unique_ptr.

Cite: how to destroy an object in C++

Use `rsync` rather than `scp`

rsync is good for incremental transfers and for taking the backup.
scp is good while securely pushing or pulling the small file from or to the remote nodes.

CMAKE_BUILD_TYPE

Release: -O3 -DNDEBUG
Debug: -O0 -g
RelWithDebInfo: -O2 -g -DNDEBUG
MinSizeRel: -Os -DNDEBUG

Cite: https://stackoverflow.com/questions/48754619/what-are-cmake-build-type-debug-release-relwithdebinfo-and-minsizerel

Core dump

https://askubuntu.com/questions/1349047/where-do-i-find-core-dump-files-and-how-do-i-view-and-analyze-the-backtrace-st

Systemd usage

https://abhinand05.medium.com/run-any-executable-as-systemd-service-in-linux-21298674f66f

Command to list services that start on startup?

sudo systemctl --all list-unit-files --type=service

cite: https://askubuntu.com/questions/218/command-to-list-services-that-start-on-startup

Convert PDF to JPEG

pdftoppm -jpeg input.pdf > out.jpeg

ABI problem from CasADi (installed by `pip`)

Solution: Building CasADi from sources

cmake -Bbuild -GNinja -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=$HOME/mylibs -DWITH_IPOPT=ON

References

CAUTION Pinocchio

Quaternion MUST normalize!
Use revolute joint type in URDF! (but continuous)
JointV of JointModelSphericalZYX is base_orientation_zyx_derivatives

How to install Arch

use latexmk

sudo apt-get install texlive-full
sudo apt install ttf-mscorefonts-installer
sudo fc-cache -f -v
# sudo apt install --reinstall ttf-mscorefonts-installer

books:

Creating Mirror-Image 3D Models

Step1: Filters $\to$ Transform: Flip and/or swap axis
Step2: Filters $\to$ Invert Faces Orientation

https://www.youtube.com/watch?v=0EUIVnp1V0Q&t=186s

undefined reference to symbol ‘exp@@GLIBC_2.2.5’

TARGET_LINK_LIBRARIES(exe -lm ${LIBS})

libm - C math library

https://askubuntu.com/questions/527665/undefined-reference-to-symbol-expglibc-2-2-5

C++ Memory Model: Migrating from X86 to ARM

https://arangodb.com/2021/02/cpp-memory-model-migrating-from-x86-to-arm/

How to use WORHP and MA57

# MA57
export LD_LIBRARY_PATH=/usr/local/lib:$LD_LIBRARY_PATH
sudo ln -s /usr/local/lib/libcoinhsl.so /usr/local/lib/libhsl.so

# WORHP
export LD_LIBRARY_PATH=/home/matheecs/Downloads/worhp_1.15-0_linux/lib:$LD_LIBRARY_PATH

cite: https://github.com/coin-or-tools/ThirdParty-HSL

MATLAB 文件夹

类文件夹: 名称以 @ 字符开头，后跟类名 (当使用多个文件定义一个类时，请使用此类型的文件夹)

包文件夹: 名称以 + 字符开头

+mypack
+mypack/pkfcn.m  % a package function
+mypack/@myClass % class folder in a package

引用包中的包成员

z = mypack.pkfcn(x,y);

a bug from `$pip install gym`

pip install setuptools==65.5.0 pip==21  # gym 0.21 installation is broken with more recent versions
pip install wheel==0.38.0

cite https://stackoverflow.com/a/77205046/14562781

参数取值范围错误

多余的括号

macOS 线程与 UI

PCL 显示问题

用好调试器 lldb/gdb

编译器优化

OpenGL 头文件

LaTeX 排版技巧

插入源代码

插入参考文献

插入摘要关键字

正下方插入文字

subfigures 插图

大括号方程组

收藏链接目录

文中添加横线

插入空行

表格线加粗

下括号

左上标

计算运行时间(单线程)

C++ 多线程计时勿用 clock()

固定翼—恒速—编队与跟踪

双目测距模块实现方案（TODO 暑假）

思索 SLAM 的真正目的

OpenCV 3.4 编译

C++11/17 编译命令

Valgrind安装(macOS High Sierra)

libcreate安装(macOS)

Google Test安装

LattePanda 启动后显示屏信号中断

Pixhawk 创建 App

MYNTEYE 相机使用参考文件 CMakeLists

在 macOS 上安装 TensorFlow

Host key verification failed

禁用 Win10 驱动签名

用pandoc实现LaTeX转Word

LaTeX导入pdf文档

树莓派软件源配置

Raspbian Lite to Raspbian PIXEL

修改树莓派swap分区大小

树莓派USB相机驱动

图像窗口打开后马上关闭

打开swf文件

Flask + Arduino Web应用程序

Arduino串口测试程序

手动添加Appimage应用图标

利用FileZilla SFTP传文件

打开Ubuntu SSH

LaTeX 格式转换 Markdown

Bochs启动黑屏

Vim 调试：termdebug 入门

ImportError in system pip wrappers after an upgrade

How do you calculate program run time in python?

WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED

Catch a Ctrl-C Event (C++)

How do I find all files containing specific text on Linux?

设置代理服务器允许局域网的其他设备共享

Ubuntu创建sudo用户

ROS生成msg/srv/action后编译package

Ubuntu系统下查看OpenCV版本

查看CUDA版本

查看CuDNN版本

使用pkg-config

用 Python & matplotlib 绘图

用 MATLAB 添加高斯和椒盐噪音

C/C++字符串分割

Latency Numbers Every Programmer Should Know

用 cloc 统计代码量

符号计算小工具 SymPy

Keynote 中插入高亮代码

macOS 终端报错 ValueError: unknown locale: UTF-8

理解 GitHub

使用 CMake/CPack/CTest/Catkin

IMU模型

安装LaTeX依赖包

学会用 Glog, Gflags, Gtest, Doxygen, GitHub CI/CD, Protobuf, clang-format

解决安装ros-kinetic-desktop-full失败

vim中添加sudo权限保存文档

Ubuntu安装中文字体解决PDF文档无法显示

解决安装`ros-kinetic-desktop-full`失败

vim中添加`sudo`权限保存文档

Use `sed` on macOS