CSC/ECE 506 Spring 2015/37 mr: Difference between revisions

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The code to parallelize:
The code to parallelize:
#include <stdio.h>
  int main()
  int main()
  {
  {
        int size = 5;
      omp_set_num_threads(6);
        int i, j;
      long sum = 1;
        int first[5][5] = { { 1, 2, 3, 4, 5 }, { 6, 7, 8, 9, 10 }, { 11, 12, 13, 14, 15 }, {16, 17, 18, 19, 20}, {21, 22, 23, 24, 25} };
      int size = 5;
        int second[5][5];
      int i, j, rowsum;
        int shift[5][5];
      int first[5][5] = { { 1, 2, 3, 4, 5 }, { 6, 7, 8, 9, 10 }, { 11, 12, 13, 14, 15 }, {16, 17, 18, 19, 20}, {21, 22, 23, 24, 25} };
        int sum = 0;
      for ( i = 0 ; i < size ; i++ ){
        for ( i = 0 ; i < size ; i++ ){
              rowsum = 0;
                for ( j = 0 ; j < size ; j++ ){
              for ( j = 0 ; j < size ; j++ ){
                        second[i][j] = first[j][i];
                      rowsum = rowsum + first[i][j];
                        sum = first[j][i] + sum;
              }
                        shift[i][j] = first[j-1][i-1];
              sum = rowsum*sum;
                }
      }
        }
      printf("sum: %d\n", sum);
        printf("Transposed matrix:-\n");
    return 0;
        for ( i = 0 ; i < size ; i++ )
        {
                for ( j = 0 ; j < size ; j++ )
                        printf("%d\t", second[i][j]);
                printf("\n");
        }
        return 0;
  }
  }
Note that this can be done using DOALL with openMP because we created a copy of the matrix!
 
== Answer 1 ==
== Answer 1 ==
  int main()
  int main()
  {
  {
omp_set_num_threads(4);
        omp_set_num_threads(6);
#pragma omp parallel
        long sum = 1;
{
         int size = 5;
         int size = 5;
         int i, j;
         int i, j, rowsum;
  #pragma omp parallel shared(rowsum, i, sum) private(j)
  {
         int first[5][5] = { { 1, 2, 3, 4, 5 }, { 6, 7, 8, 9, 10 }, { 11, 12, 13, 14, 15 }, {16, 17, 18, 19, 20}, {21, 22, 23, 24, 25} };
         int first[5][5] = { { 1, 2, 3, 4, 5 }, { 6, 7, 8, 9, 10 }, { 11, 12, 13, 14, 15 }, {16, 17, 18, 19, 20}, {21, 22, 23, 24, 25} };
        int second[5][5];
         #pragma omp for
        int shift[5][5];
        int sum = 0;
         #pragma omp parallel for default (shared)
         for ( i = 0 ; i < size ; i++ ){
         for ( i = 0 ; i < size ; i++ ){
                rowsum = 0;
                 for ( j = 0 ; j < size ; j++ ){
                 for ( j = 0 ; j < size ; j++ ){
                         second[i][j] = first[j][i];
                         rowsum = rowsum + first[i][j];
                        sum = first[j][i] + sum;
                        shift[i][j] = first[j-1][i-1];
                 }
                 }
                #pragma omp critical
                sum = rowsum*sum;
         }
         }
         printf("Transposed matrix:\n");
  }
        for ( i = 0 ; i < size ; i++ )
         printf("sum: %d\n", sum);
        {
    return 0;
                for ( j = 0 ; j < size ; j++ )
                        printf("%d\t", second[i][j]);
                printf("\n");
        }
}
        return 0;
  }
  }



Latest revision as of 04:49, 3 February 2015

A (simple) Introduction to OpenMP

How to run the samples on EOS

gcc -fopenmp hello.c -o hello

Question 1

Parallelize the following code using OpenMP


The code to parallelize:

int main()
{
      omp_set_num_threads(6);
      long sum = 1;
      int size = 5;
      int i, j, rowsum;
      int first[5][5] = { { 1, 2, 3, 4, 5 }, { 6, 7, 8, 9, 10 }, { 11, 12, 13, 14, 15 }, {16, 17, 18, 19, 20}, {21, 22, 23, 24, 25} };
      for ( i = 0 ; i < size ; i++ ){
              rowsum = 0;
              for ( j = 0 ; j < size ; j++ ){
                      rowsum = rowsum + first[i][j];
              }
              sum = rowsum*sum;
      }
      printf("sum: %d\n", sum);
   return 0;
}

Answer 1

int main()
{
       omp_set_num_threads(6);
       long sum = 1;
       int size = 5;
       int i, j, rowsum;
 #pragma omp parallel shared(rowsum, i, sum) private(j)
 {
       int first[5][5] = { { 1, 2, 3, 4, 5 }, { 6, 7, 8, 9, 10 }, { 11, 12, 13, 14, 15 }, {16, 17, 18, 19, 20}, {21, 22, 23, 24, 25} };
       #pragma omp for
       for ( i = 0 ; i < size ; i++ ){
               rowsum = 0;
               for ( j = 0 ; j < size ; j++ ){
                       rowsum = rowsum + first[i][j];
               }
               #pragma omp critical
               sum = rowsum*sum;
       }
 }
       printf("sum: %d\n", sum);
    return 0;
}

Question 2

Parallelize the code below using loop distribution


for (i=0; i<n; i++) { 
S1:  a[i] = b[i-1] * a[i+1];
S2:  b[i] = b[i] * 3;
S3:  c[i] = .2 * (c[i-1] * c[i]);
} 

After loop distribution


for(i=0; i < n; i++)  
 S1: a[i] = b[i-1] * a[i+1]; 
for(i=0; i < n; i++) 
 S3: c[i] = .2* c[i-1] * c[i];
for(i=0; i < n; i++) 
 S2: b[i] = b[i] * 3;

Now write the parallelized code in openMP using C++


#pragma omp parallel shared(a,b,c)private(i) {
 #pragma omp sections nowait
 {
       #pragma omp section
       for(i=0; i < n; i++)
         a[i] = b[i-1] * a[i+1];
       #pragma omp section
       for(i=0; i<n; i++)
        c[i] = .2* c[i-1]*c[i];
       #pragma omp section
       for(i=0; i < n; i++)
        b[i] = b[i] * 3;
  }//end omp sections
} //end omp parallel