Unable to find Eigen3 with CMake

I am kind of desperate: For my studies I need to work with Eigen and CMake. I'm able to use Eigen if I copy the whole library in the directories where my compiler looks by default but as soon as I try to find it via
find_package(Eigen3 REQUIRED)
I get the following error:


CMake Error at /usr/share/cmake/Modules/FindPackageHandleStandardArgs.cmake:148 (message):
  Could NOT find Eigen3 (missing: EIGEN3_INCLUDE_DIR EIGEN3_VERSION_OK)
  (Required is at least version "2.91.0")
Call Stack (most recent call first):
  /usr/share/cmake/Modules/FindPackageHandleStandardArgs.cmake:388 (_FPHSA_FAILURE_MESSAGE)
  FindEigen3.cmake:76 (find_package_handle_standard_args)
  CMakeLists.txt:8 (find_package)

-- Configuring incomplete, errors occurred!

Now I searched for solutions but all I those I tried (also those available on stackoverflow:
Find package Eigen3 for CMake or CMake Can't find Eigen3 ) did not work. My Eigen Version (according to the Macros in Core/util/Macros.h) is 3.2.5. I keep the Eigen directory in /usr/local/include, I use the FindEigen3.cmake which comes with the Eigen library and my CMakeLists.txt looks as follows:


cmake_minimum_required(VERSION 2.8)
project(Test)

set(CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR})
find_package(Eigen3 REQUIRED)
include_directories(${EIGEN3_INCLUDE_DIR})
message("Found Eigen3 in: ${EIGEN3_INCLUDE_DIR}")

add_executable(main test.cpp)

Has anyone an idea what's going wrong?

Kind regards, Julien

Florian

Turning my comment into an answer

The find package scripts - like FindEigen3.cmake - normally use the find_path() command to detect the package's include directory (see it's documentation for the full details).

FindEigen3.cmake uses the following code snippet:

find_path(EIGEN3_INCLUDE_DIR NAMES signature_of_eigen3_matrix_library
    PATHS
    ${CMAKE_INSTALL_PREFIX}/include
    ${KDE4_INCLUDE_DIR}
    PATH_SUFFIXES eigen3 eigen
)

So it looks in CMAKE_INSTALL_PREFIX which on Unix/Linux hosts is /usr/local by default.

The following has worked for me:

Go to the Eigen source directory and run the CMake and installation steps
```
> mkdir build
> cd build
> cmake ..
> make install
```
Then copy - as you have done - FindEigen3.cmake to your projects source directory.

Now your code does find Eigen (just changed to list(APPEND ...))

list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}")
find_package(Eigen3 REQUIRED)

References

youke

Add the path of FindEigen3.cmake before find_package(Eigen3 REQUIRED), like this:

LIST(APPEND CMAKE_MODULE_PATH "/usr/share/cmake-2.8/Modules/")
find_package(Eigen3)

来源：https://stackoverflow.com/questions/34138879/unable-to-find-eigen3-with-cmake

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eigen3