Re: Re: Problem setting buffer size for gfortran ( v 11.2)

["Bertini, Denis Dr." <D.Bertini@gsi.de>]

Hi Harald

I modified a little your test program to the following:

>>>>>>>>>>>>>>>>>>>>>>>>>>
program fio
  integer       :: stat
  character(80) :: s
  integer, parameter                :: nx = 256
  integer, parameter                :: ny = 256
  integer, parameter                :: nz = 256
  integer                :: i, j, k, l
  double precision   :: data(nx,ny,nz)

  call get_environment_variable ("GFORTRAN_FORMATTED_BUFFER_SIZE", s, status=stat)
  if (stat == 0) then
     print *, "GFORTRAN_FORMATTED_BUFFER_SIZE=",trim(s)
  else
     print *, "GFORTRAN_FORMATTED_BUFFER_SIZE not set"
  end if


     ! reset array
     data(:,:,:) = -1

     ! fill dummy data
     do i = 1, nx
        do j = 1, ny
           do k = 1, nz
              data(i,j,k) = (i+j+k) * 0.1
           end do
        end do
     end do



  open(10,file="bigfile", status="new", action="write", form='unformatted', access='stream')
  write(10) data(1:nx, 1:ny, 1:nz)
  close(10)
end program fio

>>>>>>>>>>>>>>>>>>>>>>>>


Now i set the env. variable to the following values:


export GFORTRAN_UNFORMATTED_BUFFER_SIZE=10000
export GFORTRAN_FORMATTED_BUFFER_SIZE=10000
export GFORTRAN_UNBUFFERED_ALL=n

From the output log  indeed  i got the correct env. variable as i set:


GFORTRAN_FORMATTED_BUFFER_SIZE=10000


But from strace output i got always


>>>>>>>>>>>>>>>>>>>>>>

write(3, "\0\0\0\0\0\0\10@\0\0\0\340\314\314\10@\0\0\0\240\231\231\t@\0\0\0`ff\n@"..., 8192) = 8192
write(3, "\0\0\0@33\v@\0\0\0\0\0\0\f@\0\0\0\340\314\314\f@\0\0\0\240\231\231\r@"..., 8192) = 8192
write(3, "\0\0\0`ff\16@\0\0\0@33\17@\0\0\0\0\0\0\20@\0\0\0`ff\20@"..., 8192) = 8192
write(3, "\0\0\0\340\314\314\20@\0\0\0@33\21@\0\0\0\240\231\231\21@\0\0\0\0\0\0\22@"..., 8192) = 8192
write(3, "\0\0\0`ff\22@\0\0\0\340\314\314\22@\0\0\0@33\23@\0\0\0\240\231\231\23@"..., 8192) = 8192
write(3, "\0\0\0\0\0\0\24@\0\0\0`ff\24@\0\0\0\340\314\314\24@\0\0\0@33\25@"..., 8192) = 8192
.....
>>>>>>>>>>>>>>>>>>
Showing the fixed that still a  8kiB buffer size is effectively ude in I/O...

Best
Denis
























________________________________
From: Harald Anlauf <anlauf@gmx.de>
Sent: Friday, February 25, 2022 7:28:31 PM
To: Bertini, Denis Dr.
Cc: Tobias Burnus; fortran@gcc.gnu.org
Subject: Aw: Re: Problem setting buffer size for gfortran ( v 11.2)

Hi Denis,

I and verified it works here on our Lustre with gfortran-10.3.0.
You could use:

integer       :: stat
character(80) :: s
call get_environment_variable ("GFORTRAN_FORMATTED_BUFFER_SIZE", s, status=stat)
if (stat == 0) then
   print *, "GFORTRAN_FORMATTED_BUFFER_SIZE=",trim(s)
else
   print *, "GFORTRAN_FORMATTED_BUFFER_SIZE not set"
end if
open(10,file="bigfile")
write(10,*) "data"
close(10)
end

to verify that the environment variable is set for a process/rank.
If that doesn't help, I'd suggest that it is possibly not a gfortran issue.

Cheers,
Harald


Gesendet: Freitag, 25. Februar 2022 um 18:28 Uhr
Von: "Bertini, Denis Dr." <D.Bertini@gsi.de>
An: "Tobias Burnus" <tobias@codesourcery.com>, "Harald Anlauf" <anlauf@gmx.de>
Cc: "fortran@gcc.gnu.org" <fortran@gcc.gnu.org>
Betreff: Re: Problem setting buffer size for gfortran ( v 11.2)

Hi Tobias,



So i use now in my submission script the option you were quoting i.e



> srun --export=ALL



which is actually the default as stated in the slurm documentation.

Setting the following environment to change the buffer size in both formatted/unformatted I/O 😎





export GFORTRAN_FORMATTED_BUFFER_SIZE=10000
export GFORTRAN_UNFORMATTED_BUFFER_SIZE=10000
export GFORTRAN_UNBUFFERED_ALL=n

Does not work even on gcc/gfortran 11.2



If i set the same way some environment variables for openMPI,

it is working.

So this is not related to the forwarding of environment variables

with srun.



Are the variables set correct ?

Best,

Denis



________________________________
From: Tobias Burnus <tobias@codesourcery.com>
Sent: Thursday, February 24, 2022 9:20:26 AM
To: Bertini, Denis Dr.; Harald Anlauf
Cc: fortran@gcc.gnu.org
Subject: Re: Problem setting buffer size for gfortran ( v 11.2)

Hi Denis,

On 24.02.22 09:15, Bertini, Denis Dr. via Fortran wrote:
> I can try that but on our cluster we are bound to use
>    srun (slurm).
> Do you know how to use the same functionality with srun
> to set the environment variables.

I didn't – but the manual did: srun --export=...

See: https://slurm.schedmd.com/srun.html#OPT_export_1

Good luck,

Tobias

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