Intel® Fortran Compiler
Build applications that can scale for the future with optimized code designed for Intel® Xeon® and compatible processors.
28436 Discussions

Using larger array in a Fortran subroutine


My Fortran code is below(test.f):

subroutine sub(n1,n2,wa)
implicit none
integer, intent(in)  :: n1, n2
real(4), intent(inout) :: wa(1_8:1_8*n1*n2)
integer(8) :: i, j, ms

print*, 'in sub, 1_8*n1*n2=', 1_8*n1*n2
print*, 'in sub, size of wa:', size(wa,kind=8)

!$omp parallel default(shared) private(i,j,ms)
!$omp do 
    do i=1, n1
    do j=1, n2
    enddo; enddo;
!$omp end do nowait
!$omp end parallel

print*, 'size of wa:', size(wa,kind=8)

end subroutine sub

program main
implicit none
integer, parameter :: n1=2**11,n2=2**20
real(4), allocatable :: wave(:)
integer :: ierr
integer(8) :: i

allocate(wave(1_8*n1*n2), stat=ierr)

!$omp parallel default(shared) private(i)
!$omp do
     do i=1_8,1_8*n1*n2
!$omp end do nowait
!$omp end parallel

print*, 'in main, size of wave:', size(wave,kind=8)

call sub(n1, n2, wave)

print*, wave(1_8*n1*n2)

deallocate(wave, stat=ierr)
end program main


n1 and n2 can be larger, and make sure that n1*n2 is an long integer (>2**31-1). I just want to test how to use very large array in a subroutine.

i compile with intel fortran 2015 and run on centos 7.3.1611.

I compile with: ifort -openmp -CB test.f.

the array wa in subroutine sub will make an error if I use -CB option for checking bound of an array.

This is the error information:

in main, size of wave: 2147483648
in sub, 1_8*n1*n2= 2147483648
in sub, size of wa: 0
forrtl: severe (408): fort: (2): Subscript #1 of the array WA has
value 108003329 which is greater than the upper bound of -2147483648.

the number of value in the error information is random.

When I declare wa in subroutine as real(4), intent(inout) :: wa(1), the program will run well.

If i complie with: gfortran gfortran -fopenmp -fbounds-check test.f, the program also run well.

Can someone tell me why?

0 Kudos
0 Replies