Disable eigen vectorization by default.

CMakeLists.txt

@@ -88,6 +88,7 @@ option(OGS_USE_PETSC "Use PETSc routines" OFF)
 option(OGS_USE_EIGEN "Use Eigen linear solver" ON)
 option(OGS_USE_EIGEN_UNSUPPORTED "Use Eigen unsupported modules" ON)
 option(EIGEN_NO_DEBUG "Disables Eigen's assertions" OFF)
+option(EIGEN_DONT_VECTORIZE "Disables explicit vectorization when defined." ON)
 
 set(OGS_EIGEN_DYNAMIC_SHAPE_MATRICES "Default" CACHE STRING "Use dynamically allocated shape matrices")
 set_property(CACHE OGS_EIGEN_DYNAMIC_SHAPE_MATRICES
@@ -191,6 +192,11 @@ endif()
 if (EIGEN_NO_DEBUG)
     add_definitions(-DEIGEN_NO_DEBUG)
 endif()
+
+if (EIGEN_DONT_VECTORIZE)
+    add_definitions(-DEIGEN_DONT_VECTORIZE)
+endif()
+
 if(OGS_EIGEN_DYNAMIC_SHAPE_MATRICES_INTERNAL)
     add_definitions(-DOGS_EIGEN_DYNAMIC_SHAPE_MATRICES)
 endif()