Added a simple compiler test to check if openmp is supported by the c…

…ompiler when requested.

INSTALL

@@ -0,0 +1,58 @@
+Installing MPAS
+====
+
+For general information on how to install MPAS, see https://mpas-dev.github.io.
+Additional notes on building MPAS on specific architectures are summarized here.
+
+Compiling MPAS on MacOSX (10.11 El Capitan - 10.12 Sierra)
+----------
+MPAS should compile out of the box on MacOSX with the standard (OS) clang compiler
+and the gfortran compiler. The gfortran compiler can be installed using homebrew
+(http://brew.sh), or using pre-compiled binaries from the MacOSX HPC website
+(http://hpc.soureforge.net), or it can be compiled by the user from the GNU sources.
+
+The standard clang compiler does not support OpenMP. Users wanting to compile MPAS
+with OpenMP support on MacOSX will have to install the LLVM clang compiler, which is
+accomplished easiest with homebrew. Since this alternative clang compiler is not in
+the standard search/library path, the user will have to modify the call to the clang
+and clang++ executable and add the library path to the compiler flags. Example:
+
+...
+	"FC_PARALLEL = mpif90" \
+	"CC_PARALLEL = mpicc -cc=clang" \
+	"CXX_PARALLEL = mpicxx -cxx=clang++" \
+	"FC_SERIAL = gfortran" \
+	"CC_SERIAL = clang" \
+	"CXX_SERIAL = clang++" \
+	"FFLAGS_PROMOTION = -fdefault-real-8 -fdefault-double-8" \
+	"FFLAGS_OPT = -O3 -m64 -ffree-line-length-none -fconvert=big-endian -ffree-form" \
+	"CFLAGS_OPT = -O3 -m64" \
+	"CXXFLAGS_OPT = -O3 -m64" \
+	"LDFLAGS_OPT = -O3 -m64" \
+	"FFLAGS_DEBUG = -g -m64 -ffree-line-length-none -fconvert=big-endian -ffree-form -fbounds-check -fbacktrace -ffpe-trap=invalid,zero,overflow" \
+	"CFLAGS_DEBUG = -g -m64" \
+	"CXXFLAGS_DEBUG = -O3 -m64" \
+	"LDFLAGS_DEBUG = -g -m64" \
+...
+
+would become
+
+...
+	"FC_PARALLEL = mpif90" \
+	"CC_PARALLEL = mpicc -cc=/usr/local/opt/llvm/bin/clang" \
+	"CXX_PARALLEL = mpicxx -cxx=/usr/local/opt/llvm/bin/clang++" \
+	"FC_SERIAL = gfortran" \
+	"CC_SERIAL = /usr/local/opt/llvm/bin/clang" \
+	"CXX_SERIAL = /usr/local/opt/llvm/bin/clang++" \
+	"FFLAGS_PROMOTION = -fdefault-real-8 -fdefault-double-8" \
+	"FFLAGS_OPT = -O3 -m64 -ffree-line-length-none -fconvert=big-endian -ffree-form -L/usr/local/opt/llvm/lib" \
+	"CFLAGS_OPT = -O3 -m64 -L/usr/local/opt/llvm/lib" \
+	"CXXFLAGS_OPT = -O3 -m64 -L/usr/local/opt/llvm/lib" \
+	"LDFLAGS_OPT = -O3 -m64 -L/usr/local/opt/llvm/lib" \
+	"FFLAGS_DEBUG = -g -m64 -L/usr/local/opt/llvm/lib -ffree-line-length-none -fconvert=big-endian -ffree-form -fbounds-check -fbacktrace -ffpe-trap=invalid,zero,overflow" \
+	"CFLAGS_DEBUG = -g -m64 -L/usr/local/opt/llvm/lib" \
+	"CXXFLAGS_DEBUG = -O3 -m64 -L/usr/local/opt/llvm/lib" \
+	"LDFLAGS_DEBUG = -g -m64 -L/usr/local/opt/llvm/lib" \
+...
+
+assuming that the LLVM clang compiler is installed in /usr/local/opt/llvm.

Makefile

@@ -690,7 +690,24 @@ endif
 endif
 
 
-mpas_main:
+compiler_test:
+ifeq "$(OPENMP)" "true"
+	@echo "Testing compiler for OpenMP support"
+	@echo "int main() { return 0; }" > conftest.c; $(SCC) $(CFLAGS) -o conftest.out conftest.c || \
+		(echo "$(SCC) does not support OpenMP - see INSTALL in top-level directory for more information"; rm -fr conftest.*; exit 1)
+	@echo "int main() { return 0; }" > conftest.c; $(CC) $(CFLAGS) -o conftest.out conftest.c || \
+		(echo "$(CC) does not support OpenMP - see INSTALL in top-level directory for more information"; rm -fr conftest.*; exit 1)
+	@echo "int main() { return 0; }" > conftest.cpp; $(CXX) $(CFLAGS) -o conftest.out conftest.cpp || \
+		(echo "$(CXX) does not support OpenMP - see INSTALL in top-level directory for more information"; rm -fr conftest.*; exit 1)
+	@echo "program test; stop 0; end program" > conftest.f90; $(SFC) $(FFLAGS) -o conftest.out conftest.f90 || \
+		(echo "$(SFC) does not support OpenMP - see INSTALL in top-level directory for more information"; rm -fr conftest.*; exit 1)
+	@echo "program test; stop 0; end program" > conftest.f90; $(FC) $(FFLAGS) -o conftest.out conftest.f90 || \
+		(echo "$(FC) does not support OpenMP - see INSTALL in top-level directory for more information"; rm -fr conftest.*; exit 1)
+	@rm -fr conftest.*
+endif
+
+
+mpas_main: compiler_test
 ifeq "$(AUTOCLEAN)" "true"
 	$(RM) .mpas_core_*
 endif