CODEWITHSUNDEEP
c#c++cuda
gmm
gmm

Reputation: 1030

How to do CudaMemcpy using CUdeviceptr

I'm trying to do a wrapper in a С++ DLL for CUDA, to be able to use it in C# (yeah, I know there's managedCuda and cudafy, but I still would like to try this)

The thing is, to be able to pass the pointer reference back to c#, i cant just do as usual and do the cuda malloc with float*. I was trying to manage everything with CUdeviceptr, but, even though cudaMalloc apparently works (no error given by cudaGetLastError), when I do the cudaMemcpy using the CUdevicptr variable it breaks and gives the "Invalid argument" error.

extern "C" __declspec(dllexport) void __cdecl allocateDeviceMemory(float*, CUdeviceptr,     unsigned int);

extern void allocateDeviceMemory(float* data, CUdeviceptr device_pointer, unsigned int numElements){
cudaMalloc((void**)&device_pointer,numElements * sizeof(float));
cudaError_t error = cudaGetLastError();
printf("CudaError.... 1  %s\n", cudaGetErrorString(error));

cudaMemcpy((void*)&device_pointer ,data,numElements * sizeof(float), cudaMemcpyHostToDevice);
error = cudaGetLastError();
printf("CudaError.... 2  %s\n", cudaGetErrorString(error));
}

Does anybody have any ideas about how can this be done?

Upvotes: 1

Views: 3788

Answers (1)

Pavan Yalamanchili
Pavan Yalamanchili

Reputation: 12109

Change

cudaMemcpy((void*)&device_pointer ,data,numElements * sizeof(float), cudaMemcpyHostToDevice)

to

cudaMemcpy((void *)device_pointer ,data,numElements * sizeof(float), cudaMemcpyHostToDevice

CUdeviceptr itself is a device pointer. When you are doing &device_pointer, you are sending in the pointer to the device pointer. cudaMalloc expects a pointer to pointer and works fine. cudaMemcpy however expects only a device pointer (not pointer to pointer).

  • If you want to use the driver API (i.e. use CUdeviceptr), use cuMemAlloc and cuMemcpyHtoD

  • If you want to use the runtime API use void * for memory pointers and cast them to the required type. You can use cudaMalloc and cudaMemcpy with the runtime API.

EDIT: Added edit to explicitly cast CUdeviceptr to void *. Added information about driver and device API.

Upvotes: 5

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