Error when using openmp 'collapse' directive in matlab mex

Question

Ajay Iyer 2015-3-17

1
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https://ww2.mathworks.cn/matlabcentral/answers/183709-error-when-using-openmp-collapse-directive-in-matlab-mex

评论： Ajay Iyer 2015-3-19

采纳的回答： James Tursa

在 MATLAB Online 中打开

Hi,

I am trying to optimize the code for matrix multiplication in a mex file with openmp. The code is given below.

void MatrixMultiply(double *in1,double *in2,double *out,int M, int N, int P)
{
/* Description: multiplies a MxN matrix with a NxP matrix */
int i,j,k;
omp_set_num_threads(2);
#pragma omp parallel for schedule(static) shared(in1,in2,out,M,N,P) private(i,j,k) 
   for (i= 0; i < M; i++) {
     for (j = 0; j < P; j++) {
         out[M*j + i] = 0;            
         for (k = 0; k < N; k++) {
             out[M*j + i] += in1[k*M + i]*in2[j*N + k]; 
         }
      }
   }
    return;
   }

However, when I change the directive to "#pragma omp parallel for collapse(3) schedule(static) shared(in1,in2,out,M,N,P) private(i,j,k) " I get an error - "error C3005: 'collapse' : unexpected token encountered on OpenMP 'parallel for' directive"

Any help in resolving this error would be appreciated.

Thanks!