Prev: write matrix
Next: Public review
From: Domel on 4 Jul 2008 15:18
The following code should allocate an allocatable shared array inside
the parallel construct using SINGLE clause. It generates a run time
error with ifort 10.1:

forrtl: severe (408): fort: (8): Attempt to fetch from allocatable
variable USEDD when it is not allocated

It *IS* allocated at the end of the routine RESIZE, only something
gets screwed up on the return . It is allocated inside the SINGLE
region, so no double allocation. The problem is gone if the call to
resize is replaced by explicit inlining of the routine (uncomment the
commented lines and do not call RESIZE). The problem will also go away
if the RESIZE routine is present -and called from - directly the main
file. Looks like an obvious bug to me. Any comments to open my eyes?
Thanks -- Dominik

main file:

PROGRAM NS3T
USE NS3T10
IMPLICIT NONE
CALL SETUP_A
END PROGRAM NS3T

separate file:
MODULE NS3T10
USE OMP_LIB
IMPLICIT NONE

CONTAINS

SUBROUTINE SETUP_A
INTEGER, DIMENSION(:), ALLOCATABLE :: USEDD
INTEGER :: NTH=1, MYID=1
!$OMP PARALLEL DEFAULT(SHARED) PRIVATE(NTH, MYID)
NTH = OMP_GET_NUM_THREADS()
MYID = OMP_GET_THREAD_NUM()
!$OMP SINGLE
PRINT *, NTH, MYID
CALL RESIZE(USEDD,1)
! IF(ALLOCATED(USEDD)) DEALLOCATE(USEDD)
! ALLOCATE(USEDD(1))
PRINT *, ALLOCATED(USEDD)
USEDD = 0
PRINT *, USEDD
!$OMP END SINGLE
!$OMP END PARALLEL
END SUBROUTINE SETUP_A

SUBROUTINE RESIZE(V,S)
INTEGER, DIMENSION(:), ALLOCATABLE, INTENT(INOUT) :: V
INTEGER, INTENT(IN) :: S
IF(ALLOCATED(V)) DEALLOCATE(V)
ALLOCATE(V(S))
PRINT *, 'RESIZE : ', S
END SUBROUTINE RESIZE

END MODULE NS3T10
From: Roman on 4 Jul 2008 18:35

>   INTEGER, DIMENSION(:), ALLOCATABLE, INTENT(INOUT) :: V

Hi,

When I compiled your code with /stand:f95 option,
the above line produced the following warning:

Warning: Allocatable dummy arguments is an extension of Standard
F95. [V]


Maybe that's the problem?


Roman
From: Roman on 4 Jul 2008 19:14

Hi,

Your code seems to work if the array is already allocated
before entering the parallel region:


SUBROUTINE SETUP_A
INTEGER, DIMENSION(:), ALLOCATABLE :: USEDD
INTEGER :: NTH=1, MYID=1

allocate(USEDD(1)) !!!

!$OMP PARALLEL DEFAULT(NONE) SHARED(USEDD) PRIVATE(NTH, MYID)
!$ NTH = OMP_GET_NUM_THREADS()
!$ MYID = OMP_GET_THREAD_NUM()

!$OMP SINGLE
!$ PRINT *, NTH, MYID
CALL RESIZE(USEDD, 5)

PRINT *, ALLOCATED(USEDD)
USEDD = 0
PRINT *, USEDD
!$OMP END SINGLE
!$OMP END PARALLEL

END SUBROUTINE SETUP_A
From: Domel on 5 Jul 2008 03:49
Hi, thanks for the comment. Yes indeed, the problem is the allocation
inside the parallel region. I looked through the OpenMP specifications
and did not find a requirement that allocatable arrays can not be
allocated there...
-- Dominik

On 5 Jul., 01:14, Roman <she...(a)eos.ubc.ca> wrote:
> Hi,
>
> Your code seems to work if the array is already allocated
> before entering the parallel region:
>
> SUBROUTINE SETUP_A
> INTEGER, DIMENSION(:), ALLOCATABLE :: USEDD
> INTEGER :: NTH=1, MYID=1
>
> allocate(USEDD(1)) !!!
>
> !$OMP PARALLEL DEFAULT(NONE) SHARED(USEDD) PRIVATE(NTH, MYID)
> !$ NTH = OMP_GET_NUM_THREADS()
> !$ MYID = OMP_GET_THREAD_NUM()
>
> !$OMP SINGLE
> !$ PRINT *, NTH, MYID
> CALL RESIZE(USEDD, 5)
>
> PRINT *, ALLOCATED(USEDD)
> USEDD = 0
> PRINT *, USEDD
> !$OMP END SINGLE
> !$OMP END PARALLEL
>
> END SUBROUTINE SETUP_A

From: Domel on 5 Jul 2008 03:51
Hmm, that is interesting, didn't know that, thanks. However, the thing
works without OpenMP. In addition, emitting such warning means that
the compiler is aware of the situation and handles it. So it makes me
even more confident it is a bug. -- Dominik

On 5 Jul., 00:35, Roman <she...(a)eos.ubc.ca> wrote:
> > INTEGER, DIMENSION(:), ALLOCATABLE, INTENT(INOUT) :: V
>
> Hi,
>
> When I compiled your code with /stand:f95 option,
> the above line produced the following warning:
>
> Warning: Allocatable dummy arguments is an extension of Standard
> F95. [V]
>
> Maybe that's the problem?
>
> Roman

 |  Next  |  Last
Pages: 1 2 3 4
Prev: write matrix
Next: Public review