omp parallel doesn't give any performance increase for matrix multiplication

Question

I'm using following 2 code blocks to compute matrix multiplication serially and parallel.

Serial -

double** ary1 = new double*[in];
double** ary2 = new double*[in];
double** result = new double*[in];
for (int i=0;i<in;i++){
    for (int j=0;j<in;j++){
        result[i][j] = 0;
        for(int k = 0;k<in; k++){
            result[i][j] += ary1[i][k]*ary2[k][j];
        }
    }
}

Parallel -

double** ary1 = new double*[in];
double** ary2 = new double*[in];
double** resultsP = new double*[in];
#pragma omp parallel for 
for(int i=0;i<size;i++){
  int raw = i/in;
  int column = i%in;
  double sum =0;
  for(int k = 0; k < in; k++){
       resultsP[raw][column] += ary1[raw][k]*ary2[k][column];
  }
  resultsP[raw][column] = sum;
}

I ran both in quad-core computer, but get same results. Why I don't get performance increased by running this parrellely? Does accessing ary1, ary2, resultsP shared arrays inside parellel loop cause them to run serially?

Answer 1

This has happened since '-fopenmp' flag hasn't included when compiling the code. Problem was solved by adding it.