From: "Bertini, Denis Dr." <D.Bertini@gsi.de>
To: Thomas Koenig <tkoenig@netcologne.de>, Harald Anlauf <anlauf@gmx.de>
Cc: Tobias Burnus <tobias@codesourcery.com>,
"fortran@gcc.gnu.org" <fortran@gcc.gnu.org>
Subject: Re: Problem setting buffer size for gfortran ( v 11.2)
Date: Sat, 26 Feb 2022 15:37:50 +0000 [thread overview]
Message-ID: <c63d8824456047729db4e23924d36df2@gsi.de> (raw)
In-Reply-To: <691ce537-ff39-7410-327f-ef11d89e2419@netcologne.de>
Hi Thomas,
OK so i took your example ( exact copy) and compile it
with gfortran 11.2.
Then without setting the environment variable:
export GFORTRAN_UNFORMATTED_BUFFER_SIZE=200000
i got
dbertini@lxbk0596:/lustre/rz/dbertini/fio > strace -e write ./fio
write(3, "\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"..., 408) = 408
write(3, "\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"..., 100368) = 100368
write(3, "\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"..., 100368) = 100368
write(3, "\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"..., 100368) = 100368
write(3, "\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"..., 100368) = 100368
write(3, "\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"..., 6120) = 6120
+++ exited with 0 +++
setting for example
dbertini@lxbk0596:/lustre/rz/dbertini/fio > export GFORTRAN_UNFORMATTED_BUFFER_SIZE=400000
dbertini@lxbk0596:/lustre/rz/dbertini/fio > strace -e write ./fio
write(3, "\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"..., 408) = 408
write(3, "\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"..., 200328) = 200328
write(3, "\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"..., 200328) = 200328
write(3, "\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"..., 6936) = 6936
+++ exited with 0 +++
So it seems to work right?
But do you understand the strace output in both cases ?
What means the data buffer distribution?
Is there some data alignment alforithm working in the background here?
Cheers.
Denis
________________________________
From: Thomas Koenig <tkoenig@netcologne.de>
Sent: Saturday, February 26, 2022 10:20:25 AM
To: Bertini, Denis Dr.; Harald Anlauf
Cc: Tobias Burnus; fortran@gcc.gnu.org
Subject: Re: Problem setting buffer size for gfortran ( v 11.2)
On 25.02.22 21:53, Bertini, Denis Dr. via Fortran wrote:
> It seems that the value set in the foreseen environment variable is just
> ignored.
> And always a buffer size of 8kiB is used, which is the default values
> for formatted I/O harcoded in libgfortran.
> The only way to change this value is editing and recompiling the libgfortran.
This is really strange, I also cannot reproduce this.
With the Ubuntu-supplied gfortran 9.3.0 I get (just setting a few
semi-random numbers for the unformatted buffer size).
$ cat write.f90
program main
implicit none
integer, parameter :: n=100
integer, dimension(n) :: x
integer :: i
x = [(i,i=1,n)]
open (10,file="tst.dat",form="unformatted",action="write")
do i=1,1000
write (10) x
end do
end program main
$ gfortran write.f90
$ strace -e write ./a.out
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
408) = 408
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
65688) = 65688
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
65688) = 65688
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
65688) = 65688
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
65688) = 65688
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
65688) = 65688
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
65688) = 65688
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
13464) = 13464
+++ exited with 0 +++
$ GFORTRAN_UNFORMATTED_BUFFER_SIZE=200000 strace -e write ./a.out
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
408) = 408
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
100368) = 100368
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
100368) = 100368
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
100368) = 100368
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
100368) = 100368
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
6120) = 6120
+++ exited with 0 +++
$ GFORTRAN_UNFORMATTED_BUFFER_SIZE=210000 strace -e write ./a.out
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
408) = 408
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
105264) = 105264
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
105264) = 105264
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
105264) = 105264
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
91800) = 91800
+++ exited with 0 +++
$ GFORTRAN_UNFORMATTED_BUFFER_SIZE=2100000 strace -e write ./a.out
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
408) = 408
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
407592) = 407592
+++ exited with 0 +++
$ GFORTRAN_UNFORMATTED_BUFFER_SIZE=21000000 strace -e write ./a.out
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
408) = 408
write(3,
"\220\1\0\0\1\0\0\0\2\0\0\0\3\0\0\0\4\0\0\0\5\0\0\0\6\0\0\0\7\0\0\0"...,
407592) = 407592
prev parent reply other threads:[~2022-02-26 15:37 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-23 16:10 Bertini, Denis Dr.
2022-02-23 18:26 ` Harald Anlauf
2022-02-23 18:26 ` Harald Anlauf
2022-02-23 20:28 ` Bertini, Denis Dr.
2022-02-23 20:57 ` Harald Anlauf
2022-02-23 20:57 ` Harald Anlauf
2022-02-23 20:59 ` Bertini, Denis Dr.
[not found] ` <trinity-9bf94afe-e773-4366-b0b2-ae398de80664-1645651097363@3c-app-gmx-bs49>
2022-02-23 21:23 ` Bertini, Denis Dr.
2022-02-23 21:38 ` Harald Anlauf
2022-02-24 7:57 ` Bertini, Denis Dr.
2022-02-24 8:13 ` Tobias Burnus
2022-02-24 8:15 ` Bertini, Denis Dr.
2022-02-24 8:20 ` Tobias Burnus
2022-02-25 17:28 ` Bertini, Denis Dr.
[not found] ` <trinity-59001f50-077d-424e-a648-24645944dd0c-1645813711633@3c-app-gmx-bap28>
2022-02-25 20:01 ` Bertini, Denis Dr.
2022-02-25 20:44 ` Harald Anlauf
2022-02-25 20:44 ` Harald Anlauf
2022-02-25 20:53 ` Bertini, Denis Dr.
2022-02-26 9:20 ` Thomas Koenig
2022-02-26 15:37 ` Bertini, Denis Dr. [this message]
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