On Wed, Jun 23, 2010 at 8:50 PM, Steve Reinhardt <[email protected]> wrote:
> RIght now we have the following phases for initializing SimObjects:
> 1. user script calls instantiate()
> a. call constructors
> b. connect ports
> c. call init()
> 2. user script optionally calls restoreCheckpoint()
> a. call unserialize()
> 3. user script calls simulate() for the first time
> a. call startup()
Stepping back a bit, part of the complexity stems from the interface
between the user's simulation script and the core code: when you call
instantiate(), there's no indication whether or not you'll be
restoring from a checkpoint, so we have to wait for the call to
simulate() to do the startup() code, since that's the first point
where we know that any checkpoint that's going to be loaded will be
loaded. (Which requires a separate flag in the core code to detect
the first time you call simulate()... not as pretty as it could be.)
In fact there's no reason I can see to separate instantiate() and
restoreCheckpoint(), and looking at configs/common/Simulate.py it
shouldn't be hard to get rid of the restoreCheckpoint() call and just
pass an optional checkpoint file to instantiate(). Ignoring the issue
at hand, we could simplify the status quo above to:
1. user script calls instantiate()
a. call constructors
b. connect ports
c. call init()
d. if checkpoint arg provided, call unserialize()
e. call startup()
...which seems much simpler to me.
Using that structure as a base, I'd like to add a function that does
what I proposed in my email of a few minutes ago, which is to do the
initialization that's needed only when state is not restored from a
checkpoint. There are actually two flavors of this, depending on
whether there is no checkpoint at all or there is a checkpoint but not
for this object. So you could expand step 1d above to:
if checkpoint arg provided:
for each SimObject:
if checkpoint has section for this SimObject:
call unserialize()
else:
call unserializeNoData()
else:
for each SimObject:
call initWithoutCheckpoint()
The System/Process code that's at issue right now should be moved into
initWithoutCheckpoint(), I think. I don't know that there's any need
for the unserializeNoData() method, but now might be a good time to
add it just in case.
I'm open to different names for these functions, if anyone has suggestions.
I don't mean to preclude Nate's idea of multi-phase init() and
startup() calls, but I think that's somewhat independent of the issue
I'm facing.
Thoughts?
Steve
_______________________________________________
m5-dev mailing list
[email protected]
http://m5sim.org/mailman/listinfo/m5-dev
