blob: 971cd634a5fa8e32f69f00cd35f92ed037e5bfbe [file] [log] [blame]
! { dg-do run }
! PR 83064 - this used to give wrong results.
! { dg-additional-options "-O1 -ftree-parallelize-loops=2" }
! Original test case by Christian Felter
program main
use, intrinsic :: iso_fortran_env
implicit none
integer, parameter :: nsplit = 4
integer(int64), parameter :: ne = 2**20
integer(int64) :: stride, low(nsplit), high(nsplit), i
real(real64), dimension(nsplit) :: pi
integer(int64), dimension(:), allocatable :: edof
allocate (edof(ne))
edof(1::4) = 1
edof(2::4) = 2
edof(3::4) = 3
edof(4::4) = 4
stride = ceiling(real(ne)/nsplit)
do i = 1, nsplit
high(i) = stride*i
end do
do i = 2, nsplit
low(i) = high(i-1) + 1
end do
low(1) = 1
high(nsplit) = ne
pi = 0
do concurrent (i = 1:nsplit)
pi(i) = sum(compute( low(i), high(i) ))
end do
if (abs (sum(pi) - atan(1.0d0)) > 1e-5) stop 1
contains
pure function compute( low, high ) result( ttt )
integer(int64), intent(in) :: low, high
real(real64), dimension(nsplit) :: ttt
integer(int64) :: j, k
ttt = 0
! Unrolled loop
! do j = low, high, 4
! k = 1
! ttt(k) = ttt(k) + (-1)**(j+1) / real( 2*j-1 )
! k = 2
! ttt(k) = ttt(k) + (-1)**(j+2) / real( 2*j+1 )
! k = 3
! ttt(k) = ttt(k) + (-1)**(j+3) / real( 2*j+3 )
! k = 4
! ttt(k) = ttt(k) + (-1)**(j+4) / real( 2*j+5 )
! end do
! Loop with modulo operation
! do j = low, high
! k = mod( j, nsplit ) + 1
! ttt(k) = ttt(k) + (-1)**(j+1) / real( 2*j-1 )
! end do
! Loop with subscripting via host association
do j = low, high
k = edof(j)
ttt(k) = ttt(k) + (-1.0_real64)**(j+1) / real( 2*j-1 )
end do
end function
end program main