Google App Engine

在ubuntu上面使用Google App Engine，根据官网只要export PATH=$PATH:/path/to/google_appengine/，但是后来运行python2.7 dev_appserver.py说找不到文件，只能在google_appengine的文件夹里面运行才可以。用echo $PATH可以看到google_appengine的路径，我还尝试更改.bashrc也不行，可能是路径没有放到python2.7里面。

Graph slam

最近读到一篇讲解图优化的博客，非常浅显易懂，尤其是里面的理念通过简单的例子，理论推导，程序应用等三个方面来介绍非常值得推广。

Python permission error

I am following the Head First Python, which is a great book, to develop a webapp, and then encounter some permission error of the .py file. 

Based on this, it turns out that I should use #!/usr/bin/python instead of #!/usr/bin/python3.

Latex figure position

Normally I use \begin{figure}[thpb] to include figures in Latex. However, sometimes this results in a lot of space between figures. According to here, we can use \begin{figure}[h!] to place the figures in a compact manner, so that all of them fit tightly with text.

windows转ubuntu遇到的问题

GCC

遇到了很多_m256d does not name a type之类的，好像是immintrin.h没有link好。把gcc从4.8升级到4.9解决了这个问题

Ceres

安装的时候如果遇到

Eigen compilation error: error: partial specialization of ‘std::vector<T, Eigen::aligned_allocator<U> >
就按照这里说的把internal/numeric_diff.h里面的#include <Eigen/StdVector>去掉，然后从新build。注意build好了之后是跟新usr/local/include里面的ceres

VTK

cc1plus: warning: /usr/local/lib/cmake/vtk-7.0/UseVTK.cmake: not a directory。之后会显示fatal error: vtk/vtkSmartPointer.h: No such file or directory。

我先试着把include(${VTK_USE_FILE})改成include_directories(${VTK_INCLUDES})这时候虽然不会显示warning了，但还是显示fatal error: vtk/vtkSmartPointer.h: No such file or directory

后来我发现在usr/local/include里面安装的文件夹叫vtk-7.1，需要把它改名字ie sudo rm vtk-7.1 vtk就ok了。

还有undefined reference to vtkRenderingOpenGL_AutoInit_Construct，在target_link_libraries里面加入/usr/local/lib/libvtkRenderingOpenGL-6.1.so搞定

cc1plus: warning: /usr/local/lib/cmake/vtk-7.0/UseVTK.cmake: not a directory还有一种解决办法就是include(${VTK_USE_FILE})，不写include_directories(${VTK_INCLUDES})

vtk初始化的时候用smart pointer和New()会爆出segmentation fault的error, 需要在target_link_libraries里面加入/usr/local/lib/libvtkRenderingOpenGL2-7.1.so
/usr/local/lib/libvtkInteractionStyle-7.1.so，注意这里的版本是7.1，相应的要写VTK_MODULE_INIT(vtkRenderingOpenGL2);而不是VTK_MODULE_INIT(vtkRenderingOpenGL);

liblapack

gcc 4.9提示liblapack.so: undefined reference to `ATL_dgemoveT'，根据这里，sudo apt-get remove libopenblas-base解决了问题

build速度慢

lib里面没有用的东西都删掉可以让cmake变快，如果一个package安装在了usr/local/include里面，那么lib里面的build文件夹就没用了。此外build好之后原来的source文件夹也可以删掉。

OpenCV

undefined imread等等问题，直接link到so文件上，比如在target_link_libraries之中加入${OpenCV_LIBS}/libopencv_core.so.3.1

_ZN2cv8cvtColorERKNS_11_InputArrayERKNS_12_OutputArrayEii undefined
加入#include "opencv2/imgproc.hpp"和${OpenCV_LIBS}/libopencv_imgproc.so.3.1

targets may link only to libraries. cmake is dropping the item
不用
#set(OpenCV_INCLUDE_DIRS "/home/nusuav/ms_workspace/opencv/build/include")
#set(OpenCV_LIBS "/home/nusuav/ms_workspace/opencv/build/lib")
而是用
SET("OpenCV_DIR" "/home/nusuav/ms_workspace/opencv/build/")
find_package( OpenCV )
不过虽然没有了warning，但是编译的时候报错找不到libopencv_core.so.3.1

LCM

包含lcm/lcm-cpp.hpp的时候提示找不到lcm_create，安装好lcm后需要在target_link_libraries里面加入/usr/local/lib/liblcm.so

Boost

运行的时候提示error loading libboost_system.so.1.59.0，根据这里，需要export LD_LIBRARY_PATH=/path/to/my/library，再rosrun

我用boost 1.55的时候显示has no member named ‘serialize’，据说要加入#include <boost/serialization/utility.hpp>，不过后来还是出现error，用boost 1.59就没有这个问题

boost load的archive ibinary会提示
terminate called after throwing an instance of 'boost::archive::archive_exception'
what(): incompatible native format - size of long
去掉error的方法是std::make_shared<boost::archive::binary_iarchive>(filename, 1)，而不是std::make_shared<boost::archive::binary_iarchive>(filename)，括号里面的1表示使用unsigned int

ROS

error loading librospack.so，根据这里，需要source /opt/ros/indigo/setup.bash

[rospack] Warning: error while crawling...Permission denied when I try to tab-complete your package name，根据这里和这里，似乎应该

#umount /home/useraccount/.gvfs
#rm -rf .gvfs/

不过我试过之后没有效果，重新启动之后才好了。

visual studio

在用VS build的时候，出现了code analysis的错误，发现并没有enable code anlaysis。改了code analysis中的一些东西之后发现不能保存。后来用administrator模式开启VS才解决了这个问题。

cout is not a member of std
根据这里，加入#include <iostream>

localtime_s or localtime_r
在windows里面用的localtime_s，在ubuntu中并没有定义，根据这里，可以换成localtime_r，注意input的两个参数位置对调

timestamp问题

每次显示timesstamp都是1970年的，实际应该是2016年。
这个问题debug了好久，最后终于找到问题了。load时候存储epoch的t少了两位数，用t *= 100就得到正常的值了。这是因为在从windows转换到linux的时候，std::chrono_system_clock 分别用的100-nanoseconds和nanoseconds。

检查epoch的值到底应该是多少，可以参考转换时间的网站。

ros node运行慢的问题

cmake生成的是debug模式，可以用release模式catkin_make CMAKE_BUILD_TYPE=RelWithDebInfo

编译的时候生成
init done
opengl support available

根据这里，这是一个opencv的bug，貌似没什么卵用，不用管它。

无法roslaunch
roslaunch的时候遇到process died，用sudo chmod a+wrx /dev/ttyACM0

No module named catkin_pkg.packages
Make sure that you have installed "catkin_pkg", it is up to date and on the PYTHONPATH.
用pip install catkin_pkg，问题原因可能是有不同版本的Python

Deep learning interesting applications

Painting

Today I find this, which is exactly what I longed for! It generates a painting from a simple sketch. The style transfer using a portrait by Van Gogh is extremely interesting! A web demo is available at deepart.io

Searching

Check out this live demo for searching topics from BBC news!

Semantic segmentation

A great tutorial for semantic image segmentation from Cambridge is here.

Image annotation

An image annotation web demo is this, but the server is always busy!

Deep learning for object detection and semantic labeling

Here are some good resources I found which use deep learning for object recognition:

Darknet
R-CNN

I tried darknet and used the tiny weights, it is fun to play with but the labels are limited and the output accuracy is not very high.

As for the semantic labeling, all the available codes seem to use caffe and I could not find any `hello world` example yet.