To:      J3                                    13-288
From:    Reinhold Bader
Subject: Synchronization of CHANGE TEAM and END TEAM
Date:    27 June 2013
References: N1967, N1971

Discussion:
~~~~~~~~~~~

N1967 presently specifies that for both the CHANGE TEAM and END TEAM
statements, synchronization of all images of the parent team is
required, implying that all these images are obliged to execute
these statements.
This paper relaxes the requirement, replacing it by one that
synchronization only applies to individual subteams in the
decomposition established by FORM SUBTEAM.


Edits to N1967:
~~~~~~~~~~~~~~~

[9:5-6] Delete "Except by ... the team."

[10:11-16] Replace paragraph by
"The CHANGE TEAM and END TEAM statements are image control
 statements.  When a CHANGE TEAM statement is executed, there is
 an implicit synchronization of all images in that subteam
 of the team specified by <team-variable> that includes the
 executing image. On each image of the subteam, execution of
 the segment following the statement is delayed until all the
 other images of the subteam have executed the same statement
 the same number of times. When execution of a change-team block
 finishes, there is an implicit synchronization of all images in
 the subteam. On each image of the subteam, execution of the
 segment following the END TEAM  statement is delayed until
 all the other images of the subteam have executed the same
 block the same number of times."


Edits to the standard (TS section 8):
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

~[...] denotes an addition to existing text.
x[...] denotes a removal from existing text.

On p27 of the TS, add

{In 8.5.4 SYNC IMAGES statement, edit paragraph 1 as follows}

"If <image-set> is an array expression, the value of each element
shall be positive and not greater than the number of images
~[of the current team], and there shall be no repeated values."

{In 8.5.4 SYNC IMAGES statement, edit paragraph 3 as follows}

"An <image-set> that is an asterisk specifies all images ~[of the
current team]."

{In 8.5.4 SYNC IMAGES statement, edit paragraph 4 as follows}

"Executions of SYNC IMAGES statements on images M and T correspond
 if ~[the current team of image M is the same as that of image T and]
 the number of times image M has executed a SYNC IMAGES statement with
 T in its image set ~[since the current team started execution] is the
 same as the number of times image T has  executed a SYNC IMAGES
 statement with M in its image set ~[since the current team started
 execution]."