CODEWITHSUNDEEP
cudag++nvcc
Matthew
Matthew

Reputation: 3956

How can I compile CUDA code then link it to a C++ project?

I am looking for help getting started with a project involving CUDA. My goal is to have a project that I can compile in the native g++ compiler but uses CUDA code. I understand that I have to compile my CUDA code in nvcc compiler, but from my understanding I can somehow compile the CUDA code into a cubin file or a ptx file.

Here are my questions:

  1. How do I use nvcc to compile into a cubin file or a ptx file? Don't I need a -c or something?
  2. Which file type do I want to use?
  3. What are the g++ commands to correctly compile and link the project together?

Assume the following:

  1. I have a file called "main.cpp" that has a main function in it and includes cuda.h.
  2. I have another file called "cudaFunc.cu" that has CUDA code in it. Let's say, for instance, that I want to add two integer arrays that exist in main.cpp.

Upvotes: 58

Views: 86429

Answers (3)

Matthew
Matthew

Reputation: 3956

I was able to resolve my issue with a couple of different posts including these ones. Don't forget that if you are using a 64 bit machine to link to the 64 bit library! It seams kind of obvious, but for clowns like me, that is something I forgot. Here is the make file that I now use... if you can digest this make file, you should be able to do what I was trying to do which was separate compilation of cuda code and other G++ code. Also keep in mind that you have to have the gcc, g++ compilers at certain versions (I am using g++-4.4 and it is working for me) Anyway, here is the make file...

all: program

program: cudacode.o
    g++ -o program -L/usr/local/cuda/lib64 -lcuda -lcudart main.cpp  cudacode.o 

cudacode.o:
    nvcc -c -arch=sm_20 cudacode.cu 

clean: rm -f *.o program

Hopefully you can see that the first thing I do is compile the cudacode (that has been saved as a .cu) using the nvcc compiler and -c option (also note that you may want to remove the -arch=sm_20). This created a cudacode.o. I then use the g++ compiler with the -o option and link to the lib64 library and link the -lcuda and -lcudart libraries along with compiling my main.cpp and then linking the cudacode.o. Hope this helps someone!

Upvotes: 68

harrism
harrism

Reputation: 27889

My answer to this recent question likely describes what you need.

A couple of additional notes:

  1. You don't need to compile your .cu to a .cubin or .ptx file. You need to compile it to a .o object file and then link it with the .o object files from your .cpp files compiled with g++.
  2. In addition to putting your cuda kernel code in cudaFunc.cu, you also need to put a C or C++ wrapper function in that file that launches the kernel (unless you are using the CUDA driver API, which is unlikely and not recommended). Also add a header file with the prototype of this wrapper function so that you can include it in your C++ code which needs to call the CUDA code. Then you link the files together using your standard g++ link line.

Upvotes: 17

Jean-Luc Nacif Coelho
Jean-Luc Nacif Coelho

Reputation: 1022

I found that linking the compiled cuda object code with g++ can be troublesome. Try compiling it like this:

all:
nvcc cudafile.cu mainfile.cpp -o executable

clean: rm -rf *.o

Upvotes: 12

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