Drools 1500x slower than IncrementalScoreCalculator

After being surprised that my own project was working slow, I did some performance test with Optaplanner on the projectJobScheduling example.

I was really surprised to discover that solving a problem with the same conditions, except using Drools rules instead of an IncrementalScoreCalculator would reduce the calculation by a factor of 1500 !

I made the test again, but with the an example test set provided in the standard example, i.e.projectJobScheduling, with "A-10" test set.

Here are the results after 60 seconds :

incrementalScoreCalculatorClass With <!-<moveThreadCount>AUTO</moveThreadCount>-> :
17:09:12.577 [l-2-thread-1] INFO Local Search phase (1) ended: time spent (60006), best score ([0]hard/[-3261/-612]soft), score calculation speed (94045/sec), step total (125140).
17:09:12.577 [l-2-thread-1] INFO Solving ended: time spent (60006), best score ([0]hard/[-3261/-612]soft), score calculation speed (97769/sec), phase total (2), environment mode (REPRODUCIBLE).

incrementalScoreCalculatorClass With <moveThreadCount>AUTO</moveThreadCount> :
17:03:52.604 [l-2-thread-1] INFO Local Search phase (1) ended: time spent (60015), best score ([0]hard/[-3392/-663]soft), score calculation speed (112827/sec), step total (130255).
17:03:52.604 [l-2-thread-1] INFO Solving ended: time spent (60015), best score ([0]hard/[-3392/-663]soft), score calculation speed (116470/sec), phase total (2), environment mode (REPRODUCIBLE).

scoreDrl with <moveThreadCount>AUTO</moveThreadCount>:
17:07:02.899 [l-3-thread-1] INFO Construction Heuristic phase (0) ended: time spent (60016), best score (-444init/[-97]hard/[127/-87]soft), score calculation speed (1944/sec), step total (78).
17:07:02.905 [l-3-thread-1] INFO Solving ended: time spent (60022), best score (-444init/[-97]hard/[127/-87]soft), score calculation speed (1942/sec), phase total (2), environment mode (REPRODUCIBLE).

I understood that Drools rules was the "recommended" choice, but now I doubt if it is worth using it with such bad performance.

Is it something that you are aware of ? Is there a workaround.

Many thanks again for such a great tool ! Didier