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From: JimBo on 17 Jul 2010 15:12
The following program works using intel fortran.
But what bit of the 2d array 'arr' gets used in each in each invocation to fill?

program sections

real, allocatable, dimension(:,:),target :: arr
real,pointer,dimension(:,:) :: arrptr
allocate(arr(900,900))

arr = 0
arrptr=>arr(1:480,1:480)
call fill(480,480,arrptr)
call lookagain(480,480,arrptr)
! try it again this time 'arr' does not have correct view
! but it ok in lookagain anyway
arr = 0
call fill(480,480,arr)
call lookagain(480,480,arr)
contains

subroutine lookagain(nx,ny,arr)
integer nx,ny
real arr(nx,ny)
do i = 1, 480
do j=1,480
if(arr(i,j) /= i+j)print *,'not ok here ',i,j
enddo
enddo
end subroutine lookagain
subroutine fill(nx,ny,arr)
integer nx,ny
real arr(nx,ny)
do i = 1, 480
do j=1,480
arr(i,j) = i+j
enddo
enddo
end subroutine fill

end program sections




From: glen herrmannsfeldt on 17 Jul 2010 15:29
JimBo <user(a)compgroups.net/> wrote:
> The following program works using intel fortran.
> But what bit of the 2d array 'arr' gets used in each \
> in each invocation to fill?

I believe it works as you say, and may go through a lot of work,
including copying array sections back and forth, to make
that true.

> program sections

> real, allocatable, dimension(:,:),target :: arr
> real,pointer,dimension(:,:) :: arrptr
> allocate(arr(900,900))
>
> arr = 0
> arrptr=>arr(1:480,1:480)
> call fill(480,480,arrptr)
> call lookagain(480,480,arrptr)
> ! try it again this time 'arr' does not have correct view
> ! but it ok in lookagain anyway
> arr = 0
> call fill(480,480,arr)
> call lookagain(480,480,arr)
> contains
>
> subroutine lookagain(nx,ny,arr)
> integer nx,ny
> real arr(nx,ny)
> do i = 1, 480
> do j=1,480
> if(arr(i,j) /= i+j)print *,'not ok here ',i,j
> enddo
> enddo
> end subroutine lookagain
> subroutine fill(nx,ny,arr)
> integer nx,ny
> real arr(nx,ny)
> do i = 1, 480
> do j=1,480
> arr(i,j) = i+j
> enddo
> enddo
> end subroutine fill
>
> end program sections
>
>
>
>
From: Jimbo on 17 Jul 2010 15:46
Fill declares arr to be explicit shaped array. This occurs a lot when you interface f77 routines into a new f90 program. The f90 program allocates arrays. In the first call to fill/lookagain where a pointer is passed temp's get created. But in the second call no temps get created.
This is the info provided by ifort -check all.


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