Error when running OpenCoarray example from Modern Fortran book

I was trying out the example from page 20 of Milan Curcic’s book “Modern Fortran”

program array_copy_caf
  implicit none


  integer :: array(5)[*]=0
  integer,parameter :: sender=1, reciever=2

  if (num_images() /= 2) &
       stop 'Error, this process must run on two parallel processes'

  if (this_image() == sender) array = [1,2,3,4,5]

  print '(a,i2,a,5(4x,i2))','array on proc',this_image(), &
       'before copy: ',array

  sync all

  if (this_image() == reciever) &
       array(:) = array(:)[sender]

  print '(a,i2,a,5(4x,i2))','array on proc',this_image(), &
       'after copy: ',array

end program array_copy_caf

And I get this error

[agnelo@fedora fortran experiment]$ caf array_copy_caf.f90 -o array_copy_caf
[agnelo@fedora fortran experiment]$ cafrun -n 6 ./array_copy_caf
STOP Error, this process must ruSTOP Error, this process must run on two parallel processes
STOP Error, this process must run on two parallel processes
STOP Error, this process must run on two parallel processes
STOP Error, this process must run on two parallel processes
application called MPI_Abort(MPI_COMM_WORLD, 0) - process 4
STOP Error, this process must run on two parallel processes

The output I am supposed to get is this :

array on proc 1 before copy: 1 2 3 4 5
array on proc 2 before copy: 0 0 0 0 0
array on proc 1 after copy: 1 2 3 4 5
array on proc 2 after copy: 1 2 3 4 5

Does anyone know what went wrong ?

Thanks in advance

1 Like

The code specifically expects to be run on 2 processors:

if (num_images() /= 2) &
       stop 'Error, this process must run on two parallel processes'
if (this_image() == sender) array = [1,2,3,4,5]
[...]
if (this_image() == reciever) &

[/quote]
but you run it on 6.
Try cafrun -n 2 ./array_copy_caf

2 Likes

Thank you !!