RE: sc_is_running

All,

The LRM currently says that sc_is_running shall return:

false during elaboration
false from start_of_simulation
true during initialization
true while the scheduler is running (during simulation)
false from end_of_simulation
false from the destructor of any object in the module hierarchy

The LRM does not directly relate the behavior of sc_is_running to sc_stop

The LRM says that sc_stop causes the scheduler to halt, which in turn
causes end_of_simulation to be called

The LRM says nothing about what happens if sc_stop is NOT called: by
inference, simulation just "runs off the end", but sc_is_running is
required to be false in the module destructors

The LRM says that a simulator that does not make use of sc_start shall
call end_of_simulation "at the very end of simulation" regardless of
whether sc_stop is called. The OSCI simulator, does make use of sc_start,
but does not call end_of_simulation unless sc_stop has been called (and is
therefore 1666-compliant).

If sc_stop is called, the OSCI sim behaves as expected.
If sc_stop is not called, the OSCI sim has sc_is_running() == true on
return from sc_start() and in the destructors, CONTRADICTING the LRM

As Tor says, sc_is_running() is indeed true up until the end_of_simulation
callbacks.

Mac's check will indeed work

My gripe was that the value of sc_is_running() on return from sc_start()
has to be inferred from the above rules. If sc_stop has been called then
everything is clear: sc_is_running() will be false. But what if sc_stop
has not been called?

- Is an implementation allowed to insert end_of_simulation() callbacks
before returning from sc_start?
- The OSCI sim has sc_is_running() == true in the destructors. Is this a
bug, or should we change the LRM?

I just want to make these details explicit.

Cheers,

John A
Nit-picker.

From:
"Michael (Mac) McNamara" <mcnamara@cadence.com>
To:
"Jeremiassen, Tor" <tor@ti.com>, Bishnupriya Bhattacharya
<bpriya@cadence.com>, "john.aynsley@doulos.com" <john.aynsley@doulos.com>,
"systemc-p1666-technical@eda.org" <systemc-p1666-technical@eda.org>
Date:
25/03/2010 16:17
Subject:
RE: sc_is_running

Or perhaps sc_is_running() should return false during the
end_of_simulation call backs, so they could be coded to check this status
in order to guide their behavior. For example, a given routine that is
called in general, and also from end_of_simulation call backs might want
to check sc_is_running before invoking an action that would schedule
something.
 
 
Michael McNamara
VP&GM System Software
Cadence Design Systems
mcnamara@cadence.com
From: owner-systemc-p1666-technical@eda.org [
mailto:owner-systemc-p1666-technical@eda.org] On Behalf Of Jeremiassen,
Tor
Sent: Thursday, March 25, 2010 4:26 AM
To: Bishnupriya Bhattacharya; john.aynsley@doulos.com;
systemc-p1666-technical@eda.org
Subject: RE: sc_is_running
 
That sounds good. In fact, it would seem reasonable for sc_is_running() to
be true up until the end_of_simulation callbacks.
 
Tor
 

---
Tor Jeremiassen, Ph.D.
Simulation and Modeling CTO
SDO Foundational Tools
Texas Instruments                    Ph:    281 274 3483
P.O. Box 1443, MS 730                Fax:   281 274 2703
Houston, TX 77251-1443               Email: tor@ti.com
From: owner-systemc-p1666-technical@eda.org [
mailto:owner-systemc-p1666-technical@eda.org] On Behalf Of Bishnupriya 
Bhattacharya
Sent: Thursday, March 25, 2010 4:34 AM
To: john.aynsley@doulos.com; systemc-p1666-technical@eda.org
Subject: RE: sc_is_running
 
John,
 
If I understrand your question correctly, in between or after calls to 
sc_start(), sc_is_running() should return true if simulation has not 
ended, and false otherwise. For example, see code below.
 
int sc_main(...) {
  ...
  sc_start(100, SC_NS);  <---------------- sc_stop() is not called and 
sc_start() returns to sc_main
  assert(sc_is_running() == true);
  sc_start(); <---------------- sc_stop() is called from a thread process 
at time 200 ns, and sc_start() returns to sc_main
  assert(sc_is_running() == false);
  return 0;
} 
 
non-OSCI simulators may have other ways of ending simulation besides 
sc_stop(), but the behavior of sc_is_running() will still be the same if 
the wording is done in terms of "end of simulation" instead of in terms of 
sc_stop(), which is what the current wording is. 
 
Does that sound right?
 
Thanks,
-Bishnupriya
 
From: owner-systemc-p1666-technical@eda.org [
mailto:owner-systemc-p1666-technical@eda.org] On Behalf Of 
john.aynsley@doulos.com
Sent: Thursday, March 25, 2010 2:28 PM
To: systemc-p1666-technical@eda.org
Subject: sc_is_running
The LRM is ambiguous about the value of sc_is_running() when called from 
sc_main between or after calls to sc_start(). In the OSCI implementation, 
sc_is_running returns true between or after calls to sc_start(), but then 
the OSCI sim does not call end_of_simulation unless sc_stop is explicitly 
called. 
Comments? Do we want the LRM to specific the value of sc_is_running() as 
per the behavior of the OSCI sim? 
Thanks 
John A 
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