Search code examples
c++multithreadingparallel-processingopenmpmex

OpenMP Matrix-Vector Multiplication Executes on Only One Thread

I have this code (outlined below) for parallelizing matrix-vector multiplication. But whenever I run it, I discover that it is executing on just one thread (even though I specified 4). How can I separate parts of the parallel code to run on separate threads. Any help will be highly appreciated. Thanks

int nthreads;
nthreads = 4;    
omp_set_num_threads(nthreads);
chunk = m/nthreads;

  #pragma omp parallel for private(i,j,H) schedule(static,chunk)
  for (i=0; i<m; i++ ){ 
    C[i]=0;
     for (j=0; j<p; j++) {
       int H = omp_get_thread_num();
       C[i] += (A[i+(j*m)]*B[j]);
   }              
 }
Solution

  • Did you include this snippet in #pragma omp parallel{...} or you might be missing the word parallel?