Loop nest parallelized with !$omp parallel do collapse() does not run

[styc]

Compile the following test program ifort 13.0.

[fortran]program test integer i, j double precision, allocatable :: a(:, :) allocate(a(5, 6)) !$omp parallel do collapse(2) private(i, j) do j = 1, 6 do i = 1, 5 a(i, j) = i * 10 + j end do end do !$omp end parallel do print *, a !$omp parallel do collapse(2) private(i, j) do i = 1, size(a, 1) do j = 1, size(a, 2) !$omp critical print *, a(i, j) !$omp end critical end do end do !$omp end parallel do end program[/fortran]

When the program is run, no output is produced from the second loop nest.

[Kevin_D_Intel]

Thank you for the nice reproducer. Unclear whether the root cause is tied to collapse or size() in the second loop nest. The second loop nest runs w/o collapse but w/size, or w/o size but w/collapse. I reported to Development (internal tracing id below) for further analysis and will update once I learn more. (Internal tracking id: DPD200237575)

[styc]

Kevin Davis (Intel) wrote:

Thank you for the nice reproducer. Unclear whether the root cause is tied to collapse or size() in the second loop nest. The second loop nest runs w/o collapse but w/size, or w/o size but w/collapse. I reported to Development (internal tracing id below) for further analysis and will update once I learn more.

(Internal tracking id: DPD200237575)

This is another troubling case involving the collapse clause.

[fortran]program test

integer s(3), e(3), i, j, k, l

s = 1
e = 64

!$omp parallel do collapse(2) private(i, j, k, l)
do l = 1, 2
do j = s(2), e(2)
do k = s(3), e(3)
do i = s(1), e(1)
!$omp critical
print *, i, j, k, l
!$omp end critical
end do
end do
end do
end do

end program[/fortran]

The program outputs only 8192 lines instead of the expected 524,288. Notice that j only ever takes two values (1 and 2).

I need an immediate workaround for this problem. Please confirm if using scalar variables for loop bounds always works.

[TimP]

I'd certainly hesitate to say "always" but I've had better luck with getting fixes for collapse with scalar loop bounds known at compile time, and my broken cases involve variable sizes.

[Kevin_D_Intel]

Unfortunately I can only produce correct results w/o collapse. I reported this case separately and requested advice for any other work around.

(Internal tracking id: DPD200237626)

(Resolution Update on 02/08/2013): This defect is fixed in the Intel Fortran Composer XE 2013 Update 2 (2013.2.146 - Linux) 

[Kevin_D_Intel]

I thought the second case was fixed in our latest XE 2013 Update 1, but that appears not to be true. Still awaiting resolution of both cases.

[jimdempseyatthecove]

For a work around, remove the collapse, swap the "do l" and "do j" lines. This will change the sequence. An alternative work around: s = 1 e = 64 !$omp parallel private(i, j, k, l) do l = 1, 2 !$omp do do j = s(2), e(2) do k = s(3), e(3) do i = s(1), e(1) !$omp critical print *, i, j, k, l !$omp end critical end do end do end do !$omp barrier end do Jim Dempsey

[jimdempseyatthecove]

(forum double posted message removed)

[Kevin_D_Intel]

The second defect (DPD200237626) is fixed in the Intel Fortran Composer XE 2013 Update 2 (2013.1.146 - Linux).

Still awaiting resolution of the first defect (DPD200237575).

(Resolution Update on 07/23/2013): This initial defect (DPD200237575) was fixed in the Intel Fortran Composer XE 2013 Update 3(2013.2.163 - Linux). 

[Kevin_D_Intel]

Pardon the overdue reply. The first defect (DPD200237575) was fixed in the Intel Fortran Composer XE 2013 Update 3 (2013.1.163 - Linux).