[CMake] Added option OGS_EIGEN_INITIALIZE_MATRICES_BY_NAN.

Defaults to ON.

See https://eigen.tuxfamily.org/dox/TopicPreprocessorDirectives.html.

CMakeLists.txt

@@ -87,6 +87,7 @@ option(OGS_USE_PETSC "Use PETSc routines" OFF)
 # Eigen
 option(OGS_USE_EIGEN "Use Eigen linear solver" ON)
 option(OGS_USE_EIGEN_UNSUPPORTED "Use Eigen unsupported modules" ON)
+option(OGS_EIGEN_INITIALIZE_MATRICES_BY_NAN "" ON)
 option(EIGEN_NO_DEBUG "Disables Eigen's assertions" OFF)
 
 set(OGS_EIGEN_DYNAMIC_SHAPE_MATRICES "Default" CACHE STRING "Use dynamically allocated shape matrices")
@@ -200,6 +201,9 @@ if(OGS_USE_EIGEN)
     if(OGS_USE_EIGEN_UNSUPPORTED)
         add_definitions(-DUSE_EIGEN_UNSUPPORTED)
     endif()
+    if(OGS_EIGEN_INITIALIZE_MATRICES_BY_NAN)
+        add_definitions(-DEIGEN_INITIALIZE_MATRICES_BY_NAN)
+    endif()
 endif()
 
 if(MSVC AND OGS_32_BIT)