Integrating mfem in existing CMake project

[samwyss]

Hello,

I apologize if this question has already been answered. I am trying to port some of the solvers in my code to mfem but am running into issues using FetchContent_Declare and FetchContent_MakeAvailable regarding the use of relative paths in the mfem CMake config.

My CMake config looks like the following.

set(MFEM_USE_MPI ON)
set(METIS_DIR ../metis-5.1.0)
set(MFEM_USE_SUNDIALS ON)
FetchContent_Declare(mfem
        GIT_REPOSITORY https://github.com/mfem/mfem.git
        GIT_TAG v4.8
        GIT_PROGRESS TRUE
        GIT_SHALLOW TRUE
        EXCLUDE_FROM_ALL
)
FetchContent_MakeAvailable(mfem)

CMake outputs the following logs.

-- Populating mfem
-- Configuring done (0.0s)
-- Generating done (0.0s)
-- Build files have been written to: <build_dir>/_deps/mfem-subbuild
[1/9] Creating directories for 'mfem-populate'
[1/9] Performing download step (git clone) for 'mfem-populate'
Cloning into 'mfem-src'...
remote: Enumerating objects: 36374, done.        
remote: Counting objects: 100% (36374/36374), done.        
remote: Compressing objects: 100% (22279/22279), done.        
remote: Total 36374 (delta 28617), reused 18644 (delta 13963), pack-reused 0 (from 0)        
Receiving objects: 100% (36374/36374), 126.20 MiB | 18.23 MiB/s, done.
Resolving deltas: 100% (28617/28617), done.
HEAD is now at a0171910 Merge pull request #4681 from mfem/mfem-4.8-dev
[2/9] Performing disconnected update step for 'mfem-populate'
-- Already at requested tag: v4.8
[3/9] No patch_disconnected step for 'mfem-populate'
[5/9] No configure step for 'mfem-populate'
[6/9] No build step for 'mfem-populate'
[7/9] No install step for 'mfem-populate'
[8/9] No test step for 'mfem-populate'
[9/9] Completed 'mfem-populate'
-- CMake version: 4.0.2
-- Loading USER_CONFIG = <build_dir>/_deps/mfem-src/config/user.cmake (NOTFOUND)
-- USE_XSDK_DEFAULTS = 'OFF'
-- Floating-point precision: MFEM_PRECISION = double
-- Found MPI_C: /usr/bin/mpicc (found version "3.1")
-- Found MPI: TRUE (found version "3.1")
-- Looking for HYPRE ...
--    in HYPRE_DIR = <build_dir>/_deps/mfem-src/../hypre/src/hypre
-- Performing Test HYPRE_USING_CUDA
-- Performing Test HYPRE_USING_CUDA - Failed
-- Performing Test HYPRE_USING_HIP
-- Performing Test HYPRE_USING_HIP - Failed
-- Found HYPRE: <build_dir>/_deps/hypre/src/hypre/lib/libHYPRE.a
-- HYPRE_INCLUDE_DIRS=<build_dir>/_deps/hypre/src/hypre/include
-- Found HYPRE version 23300
-- Found HYPRE: <build_dir>/_deps/hypre/src/hypre/lib/libHYPRE.a
-- Looking for METIS ...
--    in METIS_DIR = ../metis-5.1.0
-- Performing Test METIS_VERSION_5
-- Performing Test METIS_VERSION_5 - Success
-- Found METIS: <build_dir>/_deps/metis-5.1.0/lib/libmetis.a
-- METIS_INCLUDE_DIRS=<build_dir>/_deps/metis-5.1.0/include
-- Looking for POSIXClocks ...
--    checking library: <standard c/c++>
-- Found POSIXClocks: TRUE
-- MFEM: using package OPENMP
-- MFEM: using package HYPRE
-- MFEM: using package METIS
-- MFEM: using package SUNDIALS
-- MFEM: using package POSIXCLOCKS
-- MFEM: using package MPI_CXX
-- MFEM shared library: BUILD_SHARED_LIBS = OFF
-- MFEM build type: CMAKE_BUILD_TYPE = Debug
-- MFEM version: v4.8.0
-- MFEM git string: tags/v4.8-0-ga01719101027383954b69af1777dc828bf795d62
-- TPL_INCLUDE_DIRS = <build_dir>/_deps/hypre/src/hypre/include;<build_dir>/_deps/metis-5.1.0/include
-- Writing substitute header --> "mfem.hpp"
-- Writing substitute header --> "mfem-performance.hpp"
-- performance_ex1: add flags "-march=native -Wall -pedantic --param max-completely-peel-times=3"
-- performance_ex1p: add flags "-march=native -Wall -pedantic --param max-completely-peel-times=3"
-- Found Doxygen: /usr/bin/doxygen (found version "1.9.1") found components: doxygen dot
-- CMAKE_INSTALL_PREFIX = /usr/local
-- C Compiler: /usr/bin/mpicc 12.3.0
-- C++ Compiler: /usr/bin/mpicxx 12.3.0
-- CMake Build Type: Debug
-- C/C++ Compile Options: -O0;-Wall;-g3
-- Configuring done (78.0s)
CMake Error in cmake-build-debug/_deps/mfem-src/CMakeLists.txt:
  Target "mfem" INTERFACE_INCLUDE_DIRECTORIES property contains path:

    "<build_dir>/_deps/hypre/src/hypre/include"

  which is prefixed in the build directory.


CMake Error in cmake-build-debug/_deps/mfem-src/CMakeLists.txt:
  Target "mfem" INTERFACE_INCLUDE_DIRECTORIES property contains path:

    "<build_dir>_deps/hypre/src/hypre/include"

  which is prefixed in the build directory.Target "mfem"
  INTERFACE_INCLUDE_DIRECTORIES property contains path:

    "<build_dir>/_deps/hypre/src/hypre/include"

  which is prefixed in the source directory.


CMake Error in cmake-build-debug/_deps/mfem-src/CMakeLists.txt:
  Target "mfem" INTERFACE_INCLUDE_DIRECTORIES property contains path:

    "<build_dir>/_deps/metis-5.1.0/include"

  which is prefixed in the build directory.


CMake Error in cmake-build-debug/_deps/mfem-src/CMakeLists.txt:
  Target "mfem" INTERFACE_INCLUDE_DIRECTORIES property contains path:

    "<build_dir>/_deps/metis-5.1.0/include"

  which is prefixed in the build directory.Target "mfem"
  INTERFACE_INCLUDE_DIRECTORIES property contains path:

    "<build_dir>/_deps/metis-5.1.0/include"

  which is prefixed in the source directory.


-- Generating done (0.2s)
CMake Generate step failed.  Build files cannot be regenerated correctly.

[Failed to reload]

Where I replaced my build directory with <build_dir>.

To me, this reads as the mfem CMake configuration is prefixing the absolute paths of the metis and hypre installs which is leading to configuration errors.

Is there a known fix for this? Or is there a more desirable way to integrate mfem into existing CMake projects? Mfem is not already installed on machines I am hoping to run on hence my use of FetchContent_Declare and FetchContent_MakeAvailable.

Thanks!

[termi-official]

I usually simply work with the following minimal file

cmake_minimum_required(VERSION 3.14)

project(
    mysim
    VERSION 0.1
    LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 17)

find_package(
    MFEM
    REQUIRED
    HINTS
        ${MFEM_DIR}
        ../mfem)
message(STATUS "Found mfem config in: ${mfem_DIR} (version ${MFEM_VERSION})")

add_subdirectory(src)

and build mfem manually in a separate folder.

[samwyss]

Thanks @termi-official! I am not sure why I didn't try that earlier. I am marking this as the answer.