How to separate CUDA code into multiple files

c, c++, cuda, visual-studio-2008

Solution

You are including `mykernel.cu` in `kernelsupport.cu`, when you try to link the compiler sees mykernel.cu twice. You'll have to create a header defining TestDevice and include that instead.

re comment:

Something like this should work

// MyKernel.h
#ifndef mykernel_h
#define mykernel_h
__global__ void TestDevice(int* devicearray);
#endif

and then change the including file to

//KernelSupport.cu
#ifndef _KERNEL_SUPPORT_
#define _KERNEL_SUPPORT_

#include <iostream>
#include <MyKernel.h>
// ...

re your edit

As long as the header you use in c++ code doesn't have any cuda specific stuff (`__kernel__`,`__global__`, etc) you should be fine linking c++ and cuda code.

Problem

I am trying separate a CUDA program into two separate .cu files in effort to edge closer to writing a real app in C++. I have a simple little program that: Allocates a memory on the host and the device. Initializes the host array to a series of numbers. Copies the host array to a device array Finds the square of all the elements in the array using a device kernel Copies the device array back to the host array Prints the results This works great if I put it all in one .cu file and run it. When I split it into two separate files I start getting linking errors. Like all my recent questions, I know this is something small, but what is it? KernelSupport.cu ``` #ifndef _KERNEL_SUPPORT_ #define _KERNEL_SUPPORT_ #include <iostream> #include <MyKernel.cu> int main( int argc, char** argv) { int* hostArray; int* deviceArray; const int arrayLength = 16; const unsigned int memSize = sizeof(int) * arrayLength; hostArray = (int*)malloc(memSize); cudaMalloc((void**) &deviceArray, memSize); std::cout << "Before device\n"; for(int i=0;i<arrayLength;i++) { hostArray[i] = i+1; std::cout << hostArray[i] << "\n"; } std::cout << "\n"; cudaMemcpy(deviceArray, hostArray, memSize, cudaMemcpyHostToDevice); TestDevice <<< 4, 4 >>> (deviceArray); cudaMemcpy(hostArray, deviceArray, memSize, cudaMemcpyDeviceToHost); std::cout << "After device\n"; for(int i=0;i<arrayLength;i++) { std::cout << hostArray[i] << "\n"; } cudaFree(deviceArray); free(hostArray); std::cout << "Done\n"; } #endif ``` MyKernel.cu ``` #ifndef _MY_KERNEL_ #define _MY_KERNEL_ __global__ void TestDevice(int *deviceArray) { int idx = blockIdx.x*blockDim.x + threadIdx.x; deviceArray[idx] = deviceArray[idx]*deviceArray[idx]; } #endif ``` Build Log: ``` 1>------ Build started: Project: CUDASandbox, Configuration: Debug x64 ------ 1>Compiling with CUDA Build Rule... 1>"C:\CUDA\bin64\nvcc.exe" -arch sm_10 -ccbin "C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\bin" -Xcompiler "/EHsc /W3 /nologo /O2 /Zi /MT " -maxrregcount=32 --compile -o "x64\Debug\KernelSupport.cu.obj" "d:\Stuff\Programming\Visual Studio 2008\Projects\CUDASandbox\CUDASandbox\KernelSupport.cu" 1>KernelSupport.cu 1>tmpxft_000016f4_00000000-3_KernelSupport.cudafe1.gpu 1>tmpxft_000016f4_00000000-8_KernelSupport.cudafe2.gpu 1>tmpxft_000016f4_00000000-3_KernelSupport.cudafe1.cpp 1>tmpxft_000016f4_00000000-12_KernelSupport.ii 1>Linking... 1>KernelSupport.cu.obj : error LNK2005: __device_stub__Z10TestDevicePi already defined in MyKernel.cu.obj 1>KernelSupport.cu.obj : error LNK2005: "void __cdecl TestDevice__entry(int *)" (?TestDevice__entry@@YAXPEAH@Z) already defined in MyKernel.cu.obj 1>D:\Stuff\Programming\Visual Studio 2008\Projects\CUDASandbox\x64\Debug\CUDASandbox.exe : fatal error LNK1169: one or more multiply defined symbols found 1>Build log was saved at "file://d:\Stuff\Programming\Visual Studio 2008\Projects\CUDASandbox\CUDASandbox\x64\Debug\BuildLog.htm" 1>CUDASandbox - 3 error(s), 0 warning(s) ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== ``` I am running Visual Studio 2008 on Windows 7 64bit. Edit: I think I need to elaborate on this a little bit. The end result I am looking for here is to have a normal C++ application with something like Main.cpp with the `int main()` event and have things run from there. At certains point in my .cpp code I want to be able to reference CUDA bits. So my thinking (and correct me if there a more standard convention here) is that I will put the CUDA Kernel code into their on .cu files, and then have a supporting .cu file that will take care of talking to the device and calling kernel functions and what not.

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