OMNeT 6-pre12 fingerprint-modules filter broken due to slow dynamic cast

[edlongman]

Platform

• OMNeT++ version: OMNeT 6-pre12
• OS: Windows 10

Describe the bug
getClassDescriptorFor causes a huge slowdown of fingerprint calculation when filtering using fields. The simple Aloha simulation goes from 0.5s to over 15s

The dynamic cast from the classDescriptors array can be skipped (but with potential for risk here) since the only things that are added to the array are classDescriptors. But this is a negligible saving.

The issue with modules with no associated classDescriptor, so the entire array of classDescriptors must be looped through, doing a dynamic_cast inside doesSupport at every step along the way.

omnetpp/src/sim/cclassdescriptor.cc

Lines 271 to 294 in 00f99d5

	cClassDescriptor *cClassDescriptor::getDescriptorFor(const cObject *object)
	{
	// find descriptor by class name
	cClassDescriptor *desc = cClassDescriptor::getDescriptorFor(object->getClassName());
	if (desc)
	return desc;
	// bad luck: no descriptor for exactly this class. Try to find one for some base class.
	//XXX we could even cache the result in a {classname->descriptor} hashtable.
	cClassDescriptor *bestDesc = nullptr;
	int bestInheritanceChainLength = -1;
	cRegistrationList *array = classDescriptors.getInstance();
	for (int i = 0; i < array->size(); i++) {
	cClassDescriptor *desc = dynamic_cast<cClassDescriptor *>(array->get(i));
	if (!desc || !desc->doesSupport(const_cast<cObject*>(object)))
	continue; // skip holes
	int inheritanceChainLength = desc->getInheritanceChainLength();
	if (inheritanceChainLength > bestInheritanceChainLength) {
	bestDesc = desc;
	bestInheritanceChainLength = inheritanceChainLength;
	}
	}
	return bestDesc;
	}

To Reproduce
Run aloha sample (PureAloha1) with the following fingerprint calculation

sim-time-limit = 10000s
fingerprint = 330e-4b36/tplx
fingerprint-modules = "className=~*Host"

Compare that with fingerprint-modules = "Aloha.host*"

[edlongman]

Performance can be restored by adding a .msg file as per 6.10 of the user manual - but this is obviously not practical when using something like INET or another large library

cplusplus{{
#include <omnetpp.h>
#include "Server.h"
#include "Host.h"  
}}


namespace aloha;

class Server extends cSimpleModule
{
    @existingClass;
    @overwritePreviousDefinition;
    @descriptor(readonly);
    @icon(simple);
}

class Host extends cSimpleModule
{
    @existingClass;
    @overwritePreviousDefinition;
    @descriptor(readonly);
    @icon(simple);
}