To: J3                                                     J3/19-176
From:    John Reid
Subject: Interpretation request for intrinsic FAILED_IMAGES
Date: 2019-July-08

NUMBER: F18/nnnn
TITLE: FAILED_IMAGES intrinsic
KEYWORDS: failed images, FAILED_IMAGES
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress

QUESTION:
FAILED_IMAGES (16.9.77) provides the image indices of the images in the
specified team that are known to have failed. Paragraph 5 states that
"If the executing image has previously executed an image control
statement whose STAT= specifier assigned the value STAT_FAILED_IMAGE
from the intrinsic module ISO_FORTRAN_ENV, or referenced a collective
subroutine whose STAT argument was set to STAT_FAILED_IMAGE, at least
one image in the set of images participating in that image control
statement or collective subroutine reference shall be known to have
failed."
This means that FAILED_IMAGES might provide a very incomplete list of
failed images. What is the point of having such a poor intrinsic
function?

ANSWER:
The standard has focussed on avoiding any delay in returning from an
image control statement once a failed image has been found. However,
this makes a user wishing to write a recovery procedure ignore
FAILED_IMAGES and perform some special tests, e.g. by attempting to
synchronize with each of the other images one by one.  Edits
are provided to make it possible to use SYNC TEAM to make FAILED_IMAGES
more reliable. We have chosen SYNC TEAM rather than SYNC ALL for this
purpose because of the optional argument TEAM in FAILED_IMAGES.

EDITS:

[203:18+] In 11.6.6 SYNC TEAM statement, add a new final para:

"If the STAT= specifier in a SYNC TEAM statement is assigned the value
STAT_FAILED_IMAGE from the intrinsic module ISO_FORTRAN_ENV, any image
of the specified team that has been found to have failed shall be known
to have failed and all the other images of the team shall have been
found in execution."

[370:8] In 16.9.77 FAILED_IMAGES ([TEAM, KIND]), add at the end of
para 5:

"If the executing image has previously executed for the specified team
a SYNC TEAM statement whose STAT= specifier assigned the value
STAT_FAILED_IMAGE, every image participating in that reference that was
found to have failed shall be known to have failed and every other
image of the team shall have been found then to be in execution."