makefile for openmp by g++ ---- It is not working

Question

I want to use a makefile for my code which is going to use openmp. My source files are compiled and linked without any error. But when I run it, it uses just one processor, even though I adjust their number by for instance export OMP_NUM_THREADS=2.

The makefile is shown in the following. I would be grateful if somebody could please help me.

Best

CPP_FILES := $(wildcard src/*.cpp)
OBJ_FILES := $(addprefix obj/,$(notdir $(CPP_FILES:.cpp=.o)))

CC = g++
DEBUG = -g

INTEL=icc
ifeq ($(notdir $(CC)),$(INTEL))
CCFLAGS=-openmp -lm -lstdc++
else
CCFLAGS=-fopenmp -lm -lstdc++
endif

LD_FLAGS :=-fopenmp -Wall $(DEBUG)
#CC_FLAGS := -Wall -c $(DEBUG)


MAIN: $(OBJ_FILES)
	$(CC) $(LD_FLAGS) -o $@ $^

obj/%.o: src/%.cpp
	$(CC) $(CC_FLAGS) -c -o $@ $<

.PHONY: clean

clean:
	rm -f $(OBJ_FILES) *.o

Phil Miller Phil Miller · Accepted Answer · 2015-02-18T23:38:12

Your defined variable CCFLAGS doesn't match the variable you're using CC_FLAGS in the actual compilation rules. When you clean up and run make do the compilation lines actually show the flags you set being passed? I'd expect they shouldn't, unless the code you have here isn't a direct copy of what you're running.

For ease of debugging, could you copy and paste a terminal transcript showing the compilation and linking happening?

makefile for openmp by g++ ---- It is not working

1 Answers