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How do I use multiple inputs in mexcuda?

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jsbbs hsyhs
jsbbs hsyhs on 23 Apr 2024
Commented: jsbbs hsyhs on 24 Apr 2024
I found a and compiled it successfully. In this file, there is only one input and one output. But I'd like to verify multiple inputs and single outputs. Changed codes are as below:
* Example of how to use the mxGPUArray API in a MEX file. This example shows
* how to write a MEX function that takes a gpuArray input and returns a
* gpuArray output, e.g. B=mexFunction(A).
* Copyright 2012 The MathWorks, Inc.
#include "mex.h"
#include "gpu/mxGPUArray.h"
#include "matrix.h"
* Device code
void __global__ TimesTwo(double const * const A, double const* const C, double * const B, int const N)
/* Calculate the global linear index, assuming a 1-d grid. */
int const i = blockDim.x * blockIdx.x + threadIdx.x;
if (i < N) {
B[i] = 2.0 * A[i];
B[i+N] = 2.0 * C[i];
* Host code
void mexFunction(int nlhs, mxArray *plhs[],
int nrhs, mxArray const *prhs[])
/* Declare all variables.*/
mxGPUArray const *A, *C;
mxGPUArray *B;
double const *d_A, *d_C;
double *d_B;
int N;
char const * const errId = "parallel:gpu:mexGPUExample:InvalidInput";
char const * const errMsg = "Invalid input to MEX file.";
/* Choose a reasonably sized number of threads for the block. */
int const threadsPerBlock = 256;
int blocksPerGrid;
/* Initialize the MathWorks GPU API. */
/* Throw an error if the input is not a GPU array. */
if ((nrhs!=1) || !(mxIsGPUArray(prhs[0]))) {
mexErrMsgIdAndTxt(errId, errMsg);
A = mxGPUCreateFromMxArray(prhs[0]);
C = mxGPUCreateFromMxArray(prhs[1]);
* Verify that A really is a double array before extracting the pointer.
if (mxGPUGetClassID(A) != mxDOUBLE_CLASS) {
mexErrMsgIdAndTxt(errId, errMsg);
* Now that we have verified the data type, extract a pointer to the input
* data on the device.
d_A = (double const *)(mxGPUGetDataReadOnly(A));
d_C = (double const *)(mxGPUGetDataReadOnly(C));
/* Create a GPUArray to hold the result and get its underlying pointer. */
mwSize ndim = 2, dims[2] = {2,4};
B = mxGPUCreateGPUArray(ndim,
d_B = (double *)(mxGPUGetData(B));
* Call the kernel using the CUDA runtime API. We are using a 1-d grid here,
* and it would be possible for the number of elements to be too large for
* the grid. For this example we are not guarding against this possibility.
N = (int)(mxGPUGetNumberOfElements(A));
blocksPerGrid = (N + threadsPerBlock - 1) / threadsPerBlock;
TimesTwo<<<blocksPerGrid, threadsPerBlock>>>(d_A, d_C, d_B, N);
/* Wrap the result up as a MATLAB gpuArray for return. */
plhs[0] = mxGPUCreateMxArrayOnGPU(B);
* The mxGPUArray pointers are host-side structures that refer to device
* data. These must be destroyed before leaving the MEX function.
There is all changed codes.
And then I'll type in matlab mexcuda, the matlab tell me compiled successfully. Then I provide two matrix and tansfer them to GPU. Finally, the question is typing xxx(data_gpu1,data_gpu2) will report an error: Invalid input to MEX file. I would like to know how to make recognize multiple inputs.

Answers (1)

Joss Knight
Joss Knight on 23 Apr 2024
You have passed in two inputs but you have a check if (nrhs!=1), so you are erroring because you don't have one input. You need to change that bit.




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