strange behavior while copying an array

Hi,

I'm experiencing strange behavior of the program while copying an array.

I made a simple test code to reproduce it.

program test

integer :: ni, nj, nk
integer, allocatable :: id(:)
real*8, allocatable :: a(:,:,:), b(:,:,:)

ni = 50
nj = 50
nk = 1

allocate(a(ni,nj,nk))
allocate(b(ni,nj,nk))
allocate(id(nk))

a = 1d0

do n = 1, nk
   id(n) = nk+1-n
enddo

call copy(a,b)

print*, sum(a), sum(b)

contains

subroutine copy(aa,bb)

real*8, intent(in)  :: aa(ni,nj,nk)
real*8, intent(out) :: bb(ni,nj,nk)

do n = 1, nk
   bb(:,:,id(n)) = aa(:,:,n)
enddo

end subroutine copy

end program test

I think the program should print out the sum value of 2500 for both array a and b.

However, the program prints out 2500 for array a, but 1250 for array b.

In this test, I used intel fortran compiler 2017 initial release.

Could you give me an advice for this problem?, or is there anything I'm doing wrong?

Thanks,