https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98577
Chinoune <mehdi.chinoune at hotmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |UNCONFIRMED
Resolution|INVALID |---
--- Comment #2 from Chinoune <mehdi.chinoune at hotmail dot com> ---
program main
use iso_fortran_env
implicit none
!
integer(int32) :: count_rate_i32
integer(int64) :: t1, t2, t3, t4, t5, t6
real(real32) :: count_rate_r32
real(real64) :: count_rate_r64
!
integer(int32), parameter :: n = 2048
real(real64), allocatable :: a(:,:), b(:,:), c(:,:)
integer :: i, j, k
!
allocate( a(n,n), b(n,n), c(n,n) )
call random_number( a )
call random_number( b )
!
call system_clock( t1, count_rate_r32 )
c = matmul( a, b )
call system_clock( t2 )
!
call system_clock( t3, count_rate_i32 )
b = matmul( c, a )
call system_clock( t4 )
!
call system_clock( t5, count_rate_r64 )
a = matmul( b, c )
call system_clock( t6 )
!
print*, "count_rate_r32:", (t2-t1)/count_rate_r32
print*, "count_rate_i32:", (t4-t3)/real(count_rate_i32,real64)
print*, "count_rate_r64:", (t6-t5)/count_rate_r64
!
end program main
$ gfortran-9 -O3 bug_gcc_98577_2.f90 -o test.x
$ ./test.x
count_rate_r32: 478419744.
count_rate_i32:
479128968.57999998
count_rate_r64: 0.71684850000000000
$ gfortran-10 -O3 bug_gcc_98577_2.f90 -o test.x
$ ./test.x
count_rate_r32: 568052096.
count_rate_i32:
568763156.84800005
count_rate_r64: 0.71658250000000001
Can you explain these results?!
