ifndef COMPILER
define compiler_help
Set COMPILER to change flags (defaulting to GNU).
Available compilers are:
  CLANG CRAY GNU INTEL

endef
$(info $(compiler_help))
COMPILER=GNU
endif

ifndef TARGET
define target_help
Set TARGET to change device (defaulting to CPU).
Available targets are:
  CPU NVIDIA

endef
$(info $(target_help))
TARGET=CPU
endif

COMPILER_GNU = g++
COMPILER_INTEL = icpc
COMPILER_CRAY = CC
COMPILER_CLANG = clang++
CXX = $(COMPILER_$(COMPILER))

FLAGS_GNU = -O3 -std=c++11
FLAGS_INTEL = -O3 -std=c++11 -xHOST
FLAGS_CRAY = -O3 -hstd=c++11
FLAGS_CLANG = -O3 -std=c++11
CXXFLAGS = $(FLAGS_$(COMPILER))

# OpenMP flags for CPUs
OMP_GNU_CPU   = -fopenmp
OMP_INTEL_CPU = -qopenmp
OMP_CRAY_CPU  =
OMP_CLANG_CPU = -fopenmp=libomp

# OpenMP flags for NVIDIA
OMP_CRAY_NVIDIA  = -DOMP_TARGET_GPU
OMP_CLANG_NVIDIA = -DOMP_TARGET_GPU -fopenmp=libomp -fopenmp-targets=nvptx64-nvidia-cuda

ifndef OMP_$(COMPILER)_$(TARGET)
$(error Targeting $(TARGET) with $(COMPILER) not supported)
endif

OMP = $(OMP_$(COMPILER)_$(TARGET))

omp-stream: main.cpp OMPStream.cpp
	$(CXX) $(CXXFLAGS) -DOMP $^ $(OMP) $(EXTRA_FLAGS) -o $@

.PHONY: clean
clean:
	rm -f omp-stream