RE: P1666 surprising result with immediate notification

All,

-----Original Message-----
From: owner-systemc-p1666-technical@eda.org [mailto:owner-systemc-p1666-technical@eda.org] On Behalf Of Philipp A. Hartmann
Sent: Tuesday, January 18, 2011 9:20 PM
To: john.aynsley@doulos.com; bpriya@cadence.com
Cc: David Black; P1666 Technical WG
Subject: Re: P1666 surprising result with immediate notification

I haven't been aware of the corner case Bishnupriya has raised in her
last mail that threads may be immediately triggered by their static
sensitivity even though they yield with an explicit wait(ev), with ev
not being part of the static sensitivity. I agree, that this is
definitely bad.

[JC] So do I.

  I have the feeling that changing wait(ev) to have immediate effect
could break existing models, since then suddenly processes may be
re-triggered that currently are guaranteed to miss the notification.
This is one of the few things you can rely on with the current immediate
semantics.

[JC] Agreed.

  When prohibiting self-triggers via the static sensitivity _and_ an
immediate wait(ev), we effectively remove the possibility to trigger a
thread process from within itself. I don't think that this is a
show-stopper, since in SC_THREADs you can always skip the wait and
continue their work directly. They can't rely on any process being run
in-between anyhow.

[JC] Disagree here. You are saying that implementing a yield() statement
serve no purpose because the thread cannot rely on any process being run
in-between. It is true that a process cannot have such reliance, but for
the global effect of the simulation the yield() statement is still useful.

Jerome

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