Hi all @ scxml commons.
We had some profiling done on our scxml multi agent simulation project. Our
issue is that scxml is too slow. We need about 100,000 instances of scxml
engines for a multi agent simulation, and tests show that the approach with
scxml is over 10 times slower than an alternative but less flexible approach.
Still, the flexibility of the scxml commons project serves us very well, so we
need to look for ways to improve the performance.
For our project setup see my mailing to this list on Fri, 30 May, 20:45.
We have the following tips and improvements:
1) Now, there's a logger applied for each instance, which is inefficient.
Make default Log in SimpleContext static. In
SCXMLExecutionContext/SCXMLExecutor, it can be static final even.
public class SimpleContext implements Context, Serializable {
/** Implementation independent log category. */
private static final Log DEFAULT_LOG = LogFactory.getLog(Context.class);
private Log log = DEFAULT_LOG;
2) SimpleContext containsKey() + get() to get()
you can rewrite SimpleContext to:
public Object get(final String name) {
Object localValue = getVars().get(name);
if (localValue!=null) {
return localValue;
} else if (parent != null) {
return parent.get(name);
} else {
return null;
}
}
We think item 1) & 2) will lead to a 30-50% improvement in our scenario, and
they are very simple to apply.
3) Other issues we are not sure about:
- Status.getAllStates can probably be cached: Difficult to determine if this
can be done since the states member is writable from outside and not sure when
this getAllStates() cache should be invalidated. But it takes up quite some
time.
- SCXMLSemanticsImpl.isLegalConfig is probably a paranoia check, can we disable
it?
4) Some questions about further speed improvements:
4a) scripting:
In the configuration as given, about 10% is spend in JEXL scripting. Depending
on how much we want to do with that, we could switch to another scripting
implementation (would require some benchmarking) or maybe move some of the
scripts into the Java domain.
Do you guys have any clues about which of the provided scripting
implementations is expected to be the fastest? Are there other possibilities to
improve the scripting performance?
4b) initializing / common stuff:
What happens now is that each StateMachine engine (SCXMLExecutor) is
instantiated a thousand times, once for each agent. Maybe it's possible to move
some of the stuff to some common initialization where it is now done for each
agent. Do you see any opportunities here?
Thanks,
kind regards,
Rinke Hoekstra.
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