To: J3                                                     J3/23-221
From: John Reid & Reinhold Bader
Subject: Interp for MOVE_ALLOC with TO a coarray
Date: 2023-October-02

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NUMBER: F23/xxx
TITLE: MOVE_ALLOC with TO a coarray
KEYWORDS: MOVE_ALLOC, coarray
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress
REFERENCES: 23-007r1

QUESTION:
Was it intended that if TO is a coarray, all images of the team be
required to have corresponding coarrays?

For example, in the following program the subroutine is executed on all
images, the coarrays are allocated on all images, and coarray s is
moved to coarray t on all images. However, the coarrays t on images
1 to ne/2 do not correspond to the coarrays on images ne/2+1 to ne and
therefore cannot be accessed from each other. Was this intended?

program trouble
  real, allocatable :: a[:], b[:]
  integer :: me, ne
  allocate(a[*],b[*])
  a = 1
  b = 2
  me = this_image()
  ne = num_images()
  if (me>ne/2) then
     call sub (b)
  else
     call sub (a)
  end if
contains
  subroutine sub(t)
     real, allocatable :: s[:], t[:]
     integer :: i
     allocate(s[*], source=3.0)
     if (me==1 .or. me==ne) write(*,*) "On image",me," s=",s
     call move_alloc (s,t)
     if (me==1 .or. me==ne) write(*,*) "On image",me," t=",t
  end subroutine
end program

ANSWER:
No, these effects were not intended. An edit is supplied to require
that if TO is a coarray all images of the current team have
corresponding coarrays.

EDIT to 23-007r1:

[422:27] In 16.9.147 MOVE_ALLOC, at the end of the para labelled TO, add
"If it is a coarray, all images of the current team shall
have corresponding coarrays."

SUBMITTED BY: John Reid & Reinhold Bader

HISTORY: 23-170   m230  Submitted