AUTO Loop Schedule

AUTO Loop Schedule in OpenMP 3.0

The AUTO loop schedule is a new loop schedule introduced in OpenMP 3.0. When SCHEDULE(AUTO) is specified on a do/for loop directive, the decision regarding scheduling is delegated to the compiler and/or OpenMP runtime support library. The programmer gives the compiler and/or libmtsk the freedom to choose any possible mapping of iterations to threads in the team.

The AUTO loop schedule is described in Section 2.5.1 (p. 38) of the OpenMP specification.

Example (Fortran):

      Program Test
      integer A(10), B(10)

      A = -1
      B = 20

!$OMP PARALLEL DO PRIVATE (A), SHARED(B), SCHEDULE(AUTO)
      do i = 1, 10
         A(i) = i
         B(i) = B(i) + A(i)
      end do

      do i = 1, 10
         PRINT *, B(i)
      end do
      end


% f90 -xopenmp -xO3 test.f
% a.out
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30

Example (C/C++):

#include <stdio.h>
#include <omp.h>

#define SIZE 10

int main(void)
{
  int i;
  int buffer[SIZE];

  #pragma omp parallel for schedule(auto)
  for (i = 0; i < SIZE; i++)
    {
      buffer[i] = i;
    }

  for (i = 0; i < SIZE; i++)
    {
      printf ("%d\n", buffer[i]);
    }

  return 0;
}

 
% cc -xopenmp -xO3 test.c
% a.out
0
1
2
3
4
5
6
7
8
9

OpenMP 3.0 Features in Express 7.08

AUTO Loop Schedule

AUTO Loop Schedule in OpenMP 3.0

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