------- Additional Comments From Thomas dot Koenig at online dot de 2004-12-17
14:27 -------
I've adjusted the subject.
I've had a look at the real modulo and mod case,
but didn't quite understand it - it appeared to
be overly complicated, compared to the straightforward
formula a - floor(a/b)*b. I'm probably missing something.
Also, here's a new test case.
$ cat mod-array.f90
program main
integer, parameter :: n=16
real, dimension(n) :: ar, br, modulo_result, floor_result
integer, dimension(n) :: ai, bi , imodulo_result, ifloor_result
ai(1:4) = 5
ai(5:8) = -5
ai(9:12) = 1
ai(13:16) = -1
bi(1:4) = (/ 3,-3, 1, -1/)
bi(5:8) = bi(1:4)
bi(9:12) = bi(1:4)
bi(13:16) = bi(1:4)
ar = ai
br = bi
modulo_result = modulo(ar,br)
imodulo_result = modulo(ai,bi)
floor_result = ar-floor(ar/br)*br
ifloor_result = nint(real(ai-floor(real(ai)/real(bi))*bi))
do i=1,n
if (modulo_result(i) /= floor_result(i) ) then
print "(A,4F5.0)" ,"real case failed: ", &
ar(i),br(i), modulo_result(i), floor_result(i)
end if
if (imodulo_result(i) /= ifloor_result(i)) then
print "(A,4I5)", "int case failed: ", &
ai(i), bi(i), imodulo_result(i), ifloor_result(i)
end if
end do
end program main
$ gfortran mod-array.f90 && ./a.out
real case failed: 5. -1. -1. 0.
int case failed: 5 -1 -1 0
real case failed: -5. 1. 1. 0.
int case failed: -5 1 1 0
real case failed: 1. -1. -1. 0.
int case failed: 1 -1 -1 0
real case failed: -1. 1. 1. 0.
int case failed: -1 1 1 0
--
What |Removed |Added
----------------------------------------------------------------------------
Summary|modulo generates wrong |modulo generates wrong
|result for divisor -1 |result for divisor 1 and -1
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19032
