RE: "Scheduling Insights" for Process Control Constructs

John,

I'm not entirely happy with this scenario either. This is the case that prompted me to write up the "Scheduling Insights" section. Does that give you any insights on why it is what it is? One purpose of that section is to "enable the LRM writers to determine if the LRM rules for the process control constructs are accurate and complete".

I believe the rules do come out consistent, if resume() causes resume_event to be notified immediately, i.e. w/o the delta cycle delay. Then the lines below become

"The effect of resume() shall be the same as immediately notifying the resume_event that the target process was sensitive to".

"Note that if a process is already scheduled, and then suspended and also resumed before it executes, it shall still execute in the current delta cycle, following the rules laid down here".
Do you (or anyone else) see any gotchas with notifying the resume_event immediately? In the original specification, there wasn't a strong reason to make the notification be with a delta delay, we went with one of the 2 choices. I quickly tried out this change in the Cadence implementation, and the house didn't break down - as expected, there were process execution order changes in a couple of tests.

Thanks,
-Bishnupriya
________________________________
From: john.aynsley@doulos.com [mailto:john.aynsley@doulos.com]
Sent: Thursday, September 02, 2010 8:05 PM
To: Bishnupriya Bhattacharya
Cc: systemc-p1666-technical@eda.org
Subject: Re: "Scheduling Insights" for Process Control Constructs

Bishnupriya,

Aaaagh! 8=)

The spec says "The effect of resume() shall be the same as notifying the resume_event that the target process was sensitive to, with a delta cycle delay."

You have now added "If a process is already scheduled, and then suspended and also resumed before it executes, there shall be no effect on the process, and it shall execute in the current delta cycle as if the suspend() and resume() have cancelled each other."

These two statements seem mutually contradictory to me.

p1.resume(); // means make runnable in the next eval phase (with a delta delay)

p2.suspend();
p2.resume(); // means make runnable in the current eval phase

Duh? You are effectively saying that resume() has a history; it remembers whether or not the process was suspended at the start of the current eval phase.

John A

From: Bishnupriya Bhattacharya <bpriya@cadence.com>
To: "john.aynsley@doulos.com" <john.aynsley@doulos.com>, "systemc-p1666-technical@eda.org" <systemc-p1666-technical@eda.org>
Date: 02/08/2010 07:27
Subject: "Scheduling Insights" for Process Control Constructs

________________________________

John, All,

As promised, here is an updated process control spec with a new section 4 "Scheduling Insights" - the intent is this section will further augment and clarify the current content. Besides the addition of this section, I've also made some minor modifications. The complete list of changes is described below. Change bars are turned on, so the changes are easy to find.

Note that the changes do not include any of the clarifications/modifications that have already happened as part of the p1666 discussions so far.

Thanks,
-Bishnupriya

 * Any place that mentions behavior for "before simulation has started" has been augmented to also include "before the process has executed for the first time" to include spawned processes
 * clarification provided for suspend-resume if process is already scheduled
 * the behavior of disabling a process before it has executed for the first time has been modified to align with the behavior of disabling an already scheduled process - rationale being if dont_initialize() has not been specified then the two cases are the same
 * clarification provided for reset() on currently executing process
 * behavior of sync_reset_on() on a process before it has executed for the first time was inaccurately stated - it has been corrected
 * for some MSWord inexplicability, Section 3 had to be copied and re-pasted; so it is showing up as a change, actually it is the same as before
 * added Section 4 "Scheduling Insights"

-------------------------------------------------------------------------------------------------------------------------------------
    Bishnupriya Bhattacharya | R&D - SystemC Simulation, Debug & Analysis | Cadence
    P: +91.80.4184.1197 www.cadence.com<http://www.cadence.com/>
-------------------------------------------------------------------------------------------------------------------------------------

 [attachment "ProcessControlLWG_July2010.doc" deleted by John Aynsley/doulos]

-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.