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* [Bug libfortran/21820] New: Really, really, horrible IO performance
@ 2005-05-30 14:33 kargl at gcc dot gnu dot org
  2005-05-30 14:33 ` [Bug libfortran/21820] " kargl at gcc dot gnu dot org
                   ` (12 more replies)
  0 siblings, 13 replies; 18+ messages in thread
From: kargl at gcc dot gnu dot org @ 2005-05-30 14:33 UTC (permalink / raw)
  To: gcc-bugs

Consider the following program:

   program kl
   integer i,j,k
   integer, parameter :: m = 1000, n = 387
   real x(m,n)
   x = 1.e0
   inquire(iolength=k) (x(i,1), i=1, m)
   open(unit=1, file='foo.dat', access='direct', recl=k)
   do j = 1, n
      write(1,rec=j) (x(i,j), i=1, n)
   end do
   close(1)
   end program kl

We find the following performance on multiple executions.

kargl[225] rm foo.dat
kargl[227] gfc40 -static -o z kl.f90
kargl[228] time ./z
        0.11 real         0.05 user         0.05 sys
kargl[229] time ./z
       29.44 real         0.36 user        28.13 sys
kargl[230] time ./z
       28.77 real         0.25 user        28.07 sys
kargl[231] rm foo.dat
kargl[232] gfc41 -static -o z kl.f90
kargl[233] time ./z
        0.23 real         0.06 user         0.05 sys
kargl[234] time ./z
        0.11 real         0.05 user         0.06 sys
kargl[235] time ./z
        0.11 real         0.03 user         0.08 sys

Here gfc40 is an unpatched gfortran from 4.0.1, and
gfc41 is a patched gfortran from HEAD.  Now, image the
performance if m = 1080 and n = 25000.  Oh, the inhumanity!

See attached patch for suggested fix.

-- 
           Summary: Really, really, horrible IO performance
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libfortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: kargl at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21820


^ permalink raw reply	[flat|nested] 18+ messages in thread
end of thread, other threads:[~2005-12-09 15:09 UTC | newest]

Thread overview: 18+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
     [not found] <bug-21820-10110@http.gcc.gnu.org/bugzilla/>
2005-11-01 21:22 ` [Bug libfortran/21820] Really, really, horrible IO performance tobi at gcc dot gnu dot org
2005-11-01 22:09 ` jblomqvi at cc dot hut dot fi
2005-11-01 22:31 ` Tobias dot Schlueter at physik dot uni-muenchen dot de
2005-12-09  9:24 ` fxcoudert at gcc dot gnu dot org
2005-12-09 15:09 ` sgk at troutmask dot apl dot washington dot edu
2005-05-30 14:33 [Bug libfortran/21820] New: " kargl at gcc dot gnu dot org
2005-05-30 14:33 ` [Bug libfortran/21820] " kargl at gcc dot gnu dot org
2005-05-30 14:49 ` pinskia at gcc dot gnu dot org
2005-05-30 15:00 ` sgk at troutmask dot apl dot washington dot edu
2005-05-30 15:01 ` pinskia at gcc dot gnu dot org
2005-05-30 15:17 ` sgk at troutmask dot apl dot washington dot edu
2005-05-30 15:34 ` pinskia at gcc dot gnu dot org
2005-05-30 16:21 ` sgk at troutmask dot apl dot washington dot edu
2005-05-31  7:51 ` fxcoudert at gcc dot gnu dot org
2005-05-31 10:57 ` fxcoudert at gcc dot gnu dot org
2005-05-31 17:01 ` sgk at troutmask dot apl dot washington dot edu
2005-08-16 19:12 ` tobi at gcc dot gnu dot org
2005-09-04  9:49 ` jblomqvi at cc dot hut dot fi
2005-09-11 11:10 ` jblomqvi at cc dot hut dot fi

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