Expected: The following loop is optimized way using gfortran -O3.
------------
program prova
implicit none
integer :: i, j, Nx, Ny
parameter(Nx=10000,Ny=10000)
real(8) :: A(Nx,Ny)
do j=1,Ny
do i=1,Nx
A(i,j)=sin(1.d0+i+j);
end do
end do
end program
------------
In an equivalent C program the loop is optimized away and the run time drops
from 10.927s to 0.001s: gcc -O3
------------
#include <math.h>
#define NX 10000
#define NY 10000
int main() {
double A[NX][NY];
int i, j;
for(i = 0; i < NX; i++)
for(j = 0; j < NY; j++)
A[i][j] = sin(3.0+i+j);
return 0;
}
--
Summary: optimization: Loop not optimized away
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: middle-end
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: burnus at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31892
