eigen_ROS

This tutorial is how to use the eigen library to compute matrices, vectors, numerical solvers, and related algorithms

Table of contents

• [1. How to run C++ in ROS]
• [2. Install Eigen Library in ROS]
• [3. Compute matrices, vectors, with Eigen library]
• [4. namespace]
• [5, Templates]
• [6. Class]

Before to install eigen library we need to learn how can run C++ code in ROS

1. How to run C++ in ROS

Create a workspace

mkdir -p ~/eigen_ws/src

cd ~/eigen_ws/

catkin_make

Create a package with name test

cd eigen_ws/src
catkin_create_pkg test std_msgs rospy roscpp tf
cd ..
catkin_make

Note: Inside the pkg test now have two folders include and src; and two files CMakeLists.txt and package.xml

Copy helloworld.cpp inside the test pkg in src folder

eigen_ws/src/test/src

Modify the Cmakelist of test pkg

catkin_package(
  INCLUDE_DIRS include
  LIBRARIES test
  DEPENDS roscpp rospy tf	 
)

add_executable(helloworld src/helloworld.cpp)

add_dependencies(helloworld ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})

target_link_libraries(helloworld 
 ${catkin_LIBRARIES})

Open new terminal and run roscore

roscore

Open second terminal and run helloworld.cpp

cd eigen_ws
catkin_make
source devel/setup.bash
rosrun test helloworld

Now the code is working and we can see hello world and the number that show the msg

2. Install Eigen Library in ROS

Download FindEigen.cmake in downloads folder

the file is on

eigen_ws/src/test/use_eigen

FindEigen.cmake file should now be added to the cmak Module

Open a terminal

cd /opt/ros/melodic/share/cmake_modules/cmake/Modules/
sudo cp ~/Download/FindEigen.cmake .
password

check if FindEigen.cmake copy with ls command

ls

Copy and paste eigen.cpp in src

eigen_ws/src/test/src

Modify the package.xml in test pkg

add

<build_depend>cmake_modules</build_depend>
<exec_depend>cmake_modules</exec_depend>

modify

 <export>
    <cpp cflags="`pkg-config --cflags eigen3` -I${prefix}/include `rosboost-cfg --cflags`" 

         lflags="-Wl,-rpath,${prefix}/lib -L${prefix}/lib -lplanning_models"/>
  </export>

Modify the Cmakelist.txt in test pkg

add

find_package(cmake_modules REQUIRED)
list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake)
find_package(Eigen REQUIRED)
include_directories(${Eigen_INCLUDE_DIRS})

modify

catkin_package(
  INCLUDE_DIRS include
  LIBRARIES test
  DEPENDS Eigen roscpp rospy tf	   
)

add c++ code using eigen library

add_executable(eigen src/eigen.cpp)

add_dependencies(eigen ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})

target_link_libraries(eigen
 ${catkin_LIBRARIES}
 ${Eigen_LIBRARIES}   
)

Open new terminal and run roscore

roscore

Open second terminal and run eigen.cpp

cd eigen_ws
catkin_make
source devel/setup.bash
rosrun test eigen

3. compute matrices, vectors, with Eigen library

show many importants links

(http://ros-developer.com/2019/03/27/eigen-arrays-matrices-and-vectors-definition-initialization-and-coefficient-wise-operations/#respond) (http://ros-developer.com/tag/eigen/) (https://eigen.tuxfamily.org/dox/group__TutorialMatrixClass.html)

4. namespace

(https://www.geeksforgeeks.org/namespace-in-c/#:~:text=Namespace%20is%20a%20feature%20added,the%20same%20name%20are%20allowed) (https://www.tutorialspoint.com/cplusplus/cpp_namespaces.htm)

5. templates

(https://www.geeksforgeeks.org/templates-cpp/)