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

Thomas Koenig via Fortran Sat, 26 Feb 2022 01:20:44 -0800

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) = 408write(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) = 65688write(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) = 65688write(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) = 65688write(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) = 65688write(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) = 65688write(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) = 65688write(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) = 408write(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) = 100368write(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) = 100368write(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) = 100368write(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) = 100368write(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

+++ 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) = 408write(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) = 408write(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

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

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