To: J3                                                     J3/20-104
From: John Reid
Subject: Collective subroutines and STAT=
Date: 2020-February-18
References: 18-007r1, 19-181, 19-244

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1. Introduction

1. Introduction
This paper is a fresh request for one of the interpretations requested
in 19-181. 19-244 explains why the editor did not accept it. Here, we
make a fresh request to address the same problem. It is self-contained
and does not require the reader to consult 19-181 or 19-244.

2. Question
16.6 par. 7 contains this statement pertaining to the execution of a
collective subroutine:
"If the STAT argument is present and ... the current team contained
failed images, an error condition occurs and the value
STAT_FAILED_IMAGE from the intrinsic module ISO_FORTRAN_ENV is
assigned to the STAT argument".
Given that an image might fail during the execution of the collective
subroutine, what exactly does this require of the implementation and
is it deliverable?

3. Suggested response
This statement is stronger than was intended. A collective subroutine
is defined (3.143.2) as an "intrinsic subroutine that performs a
calculation on a team of images without requiring synchronization".
For performance reasons, it was intended that once an image has
completed its calculation it should be free to execute other statements
without waiting for the other images to do so. 16.7 para. 7 seems to
require that a synchronization of all images of the team should occur
before any are freed in order to ensure that none have failed. This
was not intended and an edit is provided to correct this.

4. Suggested edit

In 16.6 Collective subroutines, para 7, sentence 2, change
        "if the current team contained failed images"
    to
        "if the current team is detected to contain failed images".
    so that the sentence becomes
        "Otherwise, if the current team is detected to contain failed
         images, an error condition occurs and the value STAT_FAILED_IMAGE
         from the intrinsic module ISO_FORTRAN_ENV is assigned to the STAT
         argument."