------- 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=1,100000000 ! 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=1,100000000 ! 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: 0.00000000000E+00 9.99000039883E-04 9.99000039883E-04
tarray,result: 3.80941987038E-01 3.00000002608E-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
