To:      J3                                                 J3/14-157r2
From:    John Reid
Subject: A.1.2 revision
Date: 2014 June 26
References: N2007, N2013

Discussion
----------
In N2013, I suggested a change to the code in A.1.2 to make the code
tolerate failing spare images. That code was not correct. Here is a
alternative change. It uses image 1 to inquire about failed images
and set up a suitable mapping to spare images. The function
IMAGE_STATUS, proposed in 14-141r2, is used to test the spares for
failure. In case of further failures before the CHANGE TEAM statement
completes execution, a test is included after it to cause the set-up
process to be repeated if any more images have failed. I am assuming
here that if some of the images that executed the CHANGE TEAM statement
have failed but the executing image is a member of a new team without
a failed image, its value of its variable called status will not be
STAT_FAILED_IMAGE.

Edits to N2007:
---------------

[40:4] Delete "and the spare ... images".

[40:9] Delete "id, me,"
[49:9+] Add INTEGER :: id[*], me[*]

[40:22-37] Replace by
! Set up spare images as replacement for failed ones
  IF (image_status(1) == STAT_FAILED_IMAGE) &
      ERROR STOP 'cannot recover'
  IF (this_image() == 1) THEN
     failed_img = failed_images()
     k = images_used
     DO i = 1, size(failed_img)
        DO k = k+1, num_images()
           IF (image_status(k) == 0) EXIT
        END DO
        IF (k > num_images()) ERROR STOP 'cannot recover'
        me[k] = failed_img(i)
        id[k] = 1
     END DO
     images_used = k
  END IF
!
! Set up a simulation team of constant size.
! id == 2 does not participate in team execution
  FORM TEAM (id, simulation_team, NEW_INDEX=me, STAT=status)
  simulation : CHANGE TEAM (simulation_team, STAT=status)
  IF (status==STAT_FAILED_IMAGE) EXIT simulation