09-186r2
To: J3
From: Van Snyder/ Bill Long
Subject: SYNC problems, especially SYNC MEMORY
Date: 2009 May 7
Reference: 09-007r1


1.  Discussion

Various wording changes that correct or clarify the text on segments
and SYNC MEMORY are proposed.


2.  Edits


[130:12-13 6.7.1.2p3]------------------------------------------------------
Editor: Replace "each" by "every" twice.


[189:17 8.5.1p1]--------------------------------------------------------
Editor: Delete "as".


[189:18 8.5.1p2]--------------------------------------------------------
The first sentence is untrue, since SYNC MEMORY does not on its own
affect the execution ordering between images.  Other than SYNC MEMORY,
it's not the statement but execution of it that affects execution order
between images.  The fact that they divide the execution sequence on each
image into segments should be mentioned here instead of in 8.5.5.

Editor:
Replace the first sentence of p2 with

"An image control statement divides the execution sequence on an image
into segments (8.5.2)."


[192:5-6 8.5.5p1]-------------------------------------------------------
How can a segment be divided into two segments?  SYNC MEMORY is already
defined to be a segment boundary so the two segments are just sitting
there anyway.  It's just too weird to say "divides what would otherwise
be a single segment into two segments."

Editor: Replace "provides a means of dividing a segment on an image
into two segments" with "defines the boundary between two segments on
an image".


[193/194 - NOTE 8.39]--------------------------------------------------
It would be clearer to have the description in 8.5.5p3  use the
same segment labels as the example in Note 8.39. Changes to the Note
are provided:

In the 8th line of the example program segment in Note 8.39, replace

"! Preceding segment" with  "! Segment <P_i>"

In the 10th line, replace

"segment <P_i>" with  "segment <P_{i+1}>"

In the 14th line, replace

"segment <Q_j>" with  "segment <Q_{j-1}>"

In the 18th line, replace

"Subsequent segment" with  "Segment <Q_j>".


Replace the first para after the program text with:

"The DO WHILE loop does not complete until VAL is defined with the
value false. This is the cooperative synchronization that provides the
dependency that image Q does not complete the segment <Q_{j-1}> until
the CALL statement in segment <P_{i+1}> completes.  This ensures that
the execution of segment <P_i> on image P precedes execution of
segment <Q_j> on image Q."

In the third paragraph, delete the first sentence, "The definition
... of segment <P_i>."

At the end of the third paragraph, replace "<Q_j>" with "<Q_{j-1}>".