Task is to parallelize matrix multiplication with p-threads and vectorized with Intel ISPC compiler

Question

In .ispc file using pthread generates errors as follows: (1) t.ispc:2:13: Error: Illegal to return a "varying" or vector type from exported function "matrix_mult_pl" export void * matrix_mult_pl( void *arg )

(2) t.ispc:2:36: Error: Varying pointer type parameter "arg" is illegal in an exported function. export void * matrix_mult_pl( void *arg )

(3) t.ispc:6:11: Error: syntax error, unexpected 'int'. tid = *(int *)(arg); // get the thread ID assigned sequentially. ^^^

and many more errors. Coder is attached below. Kindly look into the issue of using pthreads in ISPC.

threads.c file

/**
 * Thread routine.
 * Each thread works on a portion of the 'matrix1'.
 * The start and end of the portion depend on the 'arg' which
 * is the ID assigned to threads sequentially. 
 */
void * matrix_mult_pl( void *arg )
{
  int rows, cols, j, tid, portion_size, row_start, row_end;

  tid = *(int *)(arg); // get the thread ID assigned sequentially.
  portion_size = size / num_threads;
  row_start = tid * portion_size;
  row_end = (tid+1) * portion_size;

  for (rows = row_start; rows < row_end; ++rows) { // hold row index of 'matrix1'
    for (j = 0; j < size; ++j) { // hold column index of 'matrix2'
     // hold value of a cell
      /* one pass to sum the multiplications of corresponding cells
     in the row vector and column vector. */
      for(cols=0; cols<size; cols++) { 
        result_pl[ rows ][ cols ] += matrix1[ rows ][ j ] * matrix2[ j ][ cols ];
      }
    }
  }
}

threads.ispc file

export void * matrix_mult_pl( void *arg )
{
  int rows, cols, j, tid, portion_size, row_start, row_end;

  tid = *(int *)(arg); // get the thread ID assigned sequentially.
  portion_size = size / num_threads;
  row_start = tid * portion_size;
  row_end = (tid+1) * portion_size;

  for (rows = row_start; rows < row_end; ++rows) { // hold row index of 'matrix1'
    for (j = 0; j < size; ++j) { // hold column index of 'matrix2'
     // hold value of a cell
      /* one pass to sum the multiplications of corresponding cells
     in the row vector and column vector. */
      for(cols=0; cols<size; cols++) { 
        result_pl[ rows ][ cols ] += matrix1[ rows ][ j ] * matrix2[ j ][ cols ];
      }
    }
  }
}

Why is ISPC file not vectorizing the execution with parallelization by pthreads?

To maximize the ability for us to help you, you should reduce this to a [Minimal, Reproducible Example](https://stackoverflow.com/help/minimal-reproducible-example). You might even find out the issue by doing so. — Ken Wayne VanderLinde, Apr 24 '20 at 19:47
I have done some changes to the code so that you can easily understand what I want to implement. — Hassam Khan, Apr 24 '20 at 21:12

score 1 · Accepted Answer · answered May 09 '20 at 08:06

1

The problem you're having is because ISPC defaults to varying type. int x = 0 is the same as varying int x = 0. This applies to pointer types as well void *arg as void varying * uniform arg and you can't have varying types in exported functions. When porting and first getting started with ISPC it's best to be explicit with uniform and varying keywords.

answered May 09 '20 at 08:06

pbrubaker

51
5

That's great to hear! Also if you run into issues in the future the [ispc-users Google Group](https://groups.google.com/forum/?utm_medium=email&utm_source=footer#!forum/ispc-users) is probably the best place to seek feedback. – pbrubaker May 12 '20 at 06:58

Task is to parallelize matrix multiplication with p-threads and vectorized with Intel ISPC compiler

1 Answers1