[Bug libfortran/41157] dtime not consistent in times reported
--- Comment #1 from kargl at gcc dot gnu dot org 2009-08-24 17:19 ---
(In reply to comment #0)
The following code was compiled with
gfortran -g -o test_dtime test_dtime.f
The code is given by (very similar to that given in the info file for gfortran
program test_dtime
integer(8) :: i, j, k
real, dimension(2) :: tarray
real :: result
real :: accum
call dtime(tarray, result)
print '(''tarray,result:'', 1P, 3E20.11)', tarray, result
do i=1,1 ! Just a delay
j = i * i - i
end do
call dtime(tarray, result)
print '(''tarray,result:'', 1P, 3E20.11)', tarray, result
accum = 0.e0! Should accumulate 10 times previous tarray(1)
call dtime(tarray, result)
do k=1, 10
do i=1,1! Just a delay
j = i * i - i
end do
call dtime(tarray, result)
accum = accum + tarray(1)
end do
print '(''accum ='', 1P, E20.11 )', accum
end program test_dtime
The resulting output is
tarray,result: 9.9939883E-04 9.9939883E-04 1.9987977E-03
tarray,result: 3.86941999197E-01 0.000E+00 3.86941999197E-01
accum = 1.35349416733E+01
Note that accum should be close to 10 times the value the tarray(1) above,
that
is, close to 3.8. I have no idea where the 13.5... came from.
Why should it be close to 3.8?
dtime returns the time since the start of the process?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41157
[Bug libfortran/41157] dtime not consistent in times reported
--- Comment #2 from fkrogh#gcc at mathalacarte dot com 2009-08-24 17:34
---
I had thought that was the case as well. But when I started getting some
negative times by subtracting the previous value from the current one in the
first location of the array I looked at the info file and found
Subsequent invocations of `DTIME' return values accumulated since
the previous invocation.
I modified the code to compute the times between invocations. The code now
looks like
program test_dtime
integer(8) :: i, j, k
real, dimension(2) :: tarray
real :: result
real :: accum, tarray1
real :: ptimes(10)
call dtime(tarray, result)
print '(''tarray,result:'', 1P, 3E20.11)', tarray, result
do i=1,1 ! Just a delay
j = i * i - i
end do
call dtime(tarray, result)
print '(''tarray,result:'', 1P, 3E20.11)', tarray, result
accum = 0.e0! Should accumulate 10 times previous tarray(1)
call dtime(tarray, result)
tarray1 = tarray(1)
do k=1, 10
do i=1,1! Just a delay
j = i * i - i
end do
call dtime(tarray, result)
ptimes(k) = tarray(1) - tarray1
tarray1 = tarray(1)
accum = accum + tarray(1)
end do
print '(''accum ='', 1P, E20.11 )', accum
print '(''ptimes ='', 1P, (3E20.11))', ptimes
end program test_dtime
And the output is
tarray,result: 0.000E+00 9.9939883E-04 9.9939883E-04
tarray,result: 3.80941987038E-01 3.0002608E-03 3.83941978216E-01
accum = 1.34219570160E+01
ptimes = 7.64882981777E-01 -3.78940939903E-01 7.60881841183E-01
-3.77939820290E-01 7.63881921768E-01 -3.80940914154E-01
7.63882875443E-01 -3.78940820694E-01 7.61881709099E-01
-3.78939628601E-01
There is a pattern here, but why? If dtime is getting overflows in times less
than a few seconds, there is a problem as well.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41157
[Bug libfortran/41157] dtime not consistent in times reported
--- Comment #3 from dominiq at lps dot ens dot fr 2009-08-24 17:45 --- dtime returns the time since the start of the process? The manual says: Subsequent invocations of DTIME return values accumulated since the previous invocation. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41157
[Bug libfortran/41157] dtime not consistent in times reported
--- Comment #4 from dominiq at lps dot ens dot fr 2009-08-24 18:16 --- If I am not mistaken, the dtime behavior change between 4.2 and 4.3. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41157
[Bug libfortran/41157] dtime not consistent in times reported
--- Comment #5 from kargl at gcc dot gnu dot org 2009-08-24 19:40 --- Confirmed. I have a patch. -- kargl at gcc dot gnu dot org changed: What|Removed |Added Status|UNCONFIRMED |NEW Ever Confirmed|0 |1 Last reconfirmed|-00-00 00:00:00 |2009-08-24 19:40:51 date|| http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41157
[Bug libfortran/41157] dtime not consistent in times reported
-- kargl at gcc dot gnu dot org changed: What|Removed |Added AssignedTo|unassigned at gcc dot gnu |kargl at gcc dot gnu dot org |dot org | Status|NEW |ASSIGNED Last reconfirmed|2009-08-24 19:40:51 |2009-08-24 19:41:06 date|| http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41157
[Bug libfortran/41157] dtime not consistent in times reported
--- Comment #7 from kargl at gcc dot gnu dot org 2009-08-25 01:47 --- Subject: Bug 41157 Author: kargl Date: Tue Aug 25 01:47:23 2009 New Revision: 151072 URL: http://gcc.gnu.org/viewcvs?root=gccview=revrev=151072 Log: 2009-08-24 Steven G. Kargl ka...@gcc.gnu.org PR fortran/41157 * dtime.c (dtime_sub): Fix computing time increment. * time_1.h: Add sys/types.h header. Use RUSAGE_SELF macro instead of a hardcoded 0. Modified: trunk/libgfortran/ChangeLog trunk/libgfortran/intrinsics/dtime.c trunk/libgfortran/intrinsics/time_1.h -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41157
[Bug libfortran/41157] dtime not consistent in times reported
--- Comment #8 from kargl at gcc dot gnu dot org 2009-08-25 03:30 --- Subject: Bug 41157 Author: kargl Date: Tue Aug 25 03:30:25 2009 New Revision: 151073 URL: http://gcc.gnu.org/viewcvs?root=gccview=revrev=151073 Log: 2009-08-24 Steven G. Kargl ka...@gcc.gnu.org PR fortran/41157 * dtime.c (dtime_sub): Fix computing time increment. * time_1.h: Add sys/types.h header. Use RUSAGE_SELF macro instead of a hardcoded 0. Modified: branches/gcc-4_4-branch/libgfortran/ChangeLog branches/gcc-4_4-branch/libgfortran/intrinsics/dtime.c branches/gcc-4_4-branch/libgfortran/intrinsics/time_1.h -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41157
[Bug libfortran/41157] dtime not consistent in times reported
--- Comment #9 from kargl at gcc dot gnu dot org 2009-08-25 03:33 --- Fixed on trunk and 4.4. Thanks for the bug report. -- kargl at gcc dot gnu dot org changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution||FIXED Target Milestone|--- |4.4.3 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41157
