dynamic parallelism. link error: undefined reference to 'main'

Accelerated Computing CUDA CUDA Programming and Performance
1

My cuda code works fine before I used dynamic parallelism. To allow calling a child kernel inside a parent kernel, I modified my makefile to be:

#CC=gcc                          # used C-compiler
CC=g++
CFLAGS=-O3 -fopenmp                    # release C-Compiler flags
#CFLAGS=   -g -Wall -pedantic  # debugging C-Compiler flags
INCDIRS=-I/usr/local/cuda/include
LD=g++      # used linker
LFLAGS=-O3   -lstdc++ -std=c++11  -fopenmp -lpthread        # linker flags
LIBS=-L. -lm   -lz                 # used libraries


all: mven

clean:
	rm -f *.o
	rm -f mven
help:   info


mven:  nsampen.o math.o 
	  $(LD) $(LFLAGS) -L/usr/local/cuda/lib64 -lcuda nsampen.o math.o -o mven $(LIBS) -lcudart

sampen.o: sampenv2.cu mathfunc.h
	#$(CC) -c $(CFLAGS) sampenv2.cu -o mven.o
	nvcc -std=c++11  -arch=sm_61 -c -dc sampenv2.cu -o sampen.o
nsampen.o: sampen.o math.o 
	nvcc -arch=sm_61 -dlink -o nsampen.o sampen.o math.o -lcudart

math.o: mathfunc.cpp mathfunc.h 
	$(CC) -c $(CFLAGS) mathfunc.cpp -o math.o

compiling seems to be fine, but link using g++ met the problem of "undefined reference to main and 3 others. Any suggestions?
Thank you so much!

Ze

2

add sampen.o to your final link step:

$(LD) $(LFLAGS) -L/usr/local/cuda/lib64 -lcuda sampen.o nsampen.o math.o -o mven $(LIBS) -lcudart

you may also need to add -lcudadevrt to the above final link step, depending on your actual code

I’m also not sure math.o belongs in your device-link step, but that may depend on your actual code

3

Solved as suggested. I thought the link step by nvcc had already put everything together. Many thanks.

4

It doesn’t. You could discover this by studying any of the CUDA sample codes that use dynamic parallelism, or refer to the NVCC documentation which gives example usage:

https://docs.nvidia.com/cuda/cuda-compiler-driver-nvcc/index.html#examples

Refer to the example given for “If you want to invoke the device and host linker separately, you can do:” which covers this topic exactly.

5

Proving once more that there is truth in the old adage: “If all else fails, read the instructions” :-)