diff --git a/CMakeLists.txt b/CMakeLists.txt
index 61f5d69d..9c6b08c0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -10,7 +10,7 @@ endif()
 if(CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
   message("setting intel true")
   set(IntelComp true )
-elseif(CMAKE_CXX_COMPILER_ID MATCHES "GNU*")
+elseif(CMAKE_CXX_COMPILER_ID MATCHES "GNU*" OR CMAKE_CXX_COMPILER_ID MATCHES "Clang*")
   set(GNUComp true )
 elseif(CMAKE_CXX_COMPILER_ID MATCHES "pgc*")
   set(PGIComp true )
@@ -24,13 +24,13 @@ STRING(COMPARE EQUAL ${CMAKE_BUILD_TYPE} "PRODUCTION" BUILD_PRODUCTION)
 STRING(COMPARE EQUAL ${CMAKE_BUILD_TYPE} "DEBUG" BUILD_DEBUG)
 if( (BUILD_RELEASE) OR (BUILD_PRODUCTION) )
   if(IntelComp)
-    set(CMAKE_Fortran_4_FLAGS "-O3 -auto -qopenmp -i4 -r4 -convert big_endian -assume byterecl -fp-model strict -fpp " CACHE INTERNAL "" )
-    set(CMAKE_Fortran_d_FLAGS "-O3 -auto -qopenmp -i4 -r8 -convert big_endian -assume byterecl -fp-model strict -fpp " CACHE INTERNAL "" )
-    set(CMAKE_Fortran_8_FLAGS "-O3 -auto -qopenmp -i8 -r8 -convert big_endian -assume byterecl -fp-model strict -fpp " CACHE INTERNAL "" )
+    set(CMAKE_Fortran_4_FLAGS "-O3 -auto -qopenmp -i4 -r4 -convert big_endian -assume byterecl -fp-model strict -fpp -DLSIZE=4 " CACHE INTERNAL "" )
+    set(CMAKE_Fortran_d_FLAGS "-O3 -auto -qopenmp -i4 -r8 -convert big_endian -assume byterecl -fp-model strict -fpp -DLSIZE=D " CACHE INTERNAL "" )
+    set(CMAKE_Fortran_8_FLAGS "-O3 -auto -qopenmp -i8 -r8 -convert big_endian -assume byterecl -fp-model strict -fpp -DLSIZE=8 " CACHE INTERNAL "" )
   elseif(GNUComp)
-    set(CMAKE_Fortran_4_FLAGS "-O3 -fopenmp -cpp " CACHE INTERNAL "" )
-    set(CMAKE_Fortran_d_FLAGS "-O3 -fopenmp -cpp -fdefault-real-8 " CACHE INTERNAL "" )
-    set(CMAKE_Fortran_8_FLAGS "-O3 -fopenmp -cpp -fdefault-integer-8 -fdefault-real-8 " CACHE INTERNAL "" )
+    set(CMAKE_Fortran_4_FLAGS "-O3 -fconvert=big-endian -cpp -DLSIZE=4 " CACHE INTERNAL "" )
+    set(CMAKE_Fortran_d_FLAGS "-O3 -fconvert=big-endian -cpp -fdefault-real-8 -DLSIZE=D " CACHE INTERNAL "" )
+    set(CMAKE_Fortran_8_FLAGS "-O3 -fconvert=big-endian -cpp -fdefault-integer-8 -fdefault-real-8 -DLSIZE=8 " CACHE INTERNAL "" )
   else()
     message("unknown compiler!")
     exit()