Povray 3.7 beta 31 almost stalls when specifying recursion_limit above 1.

My CPU is Intel Quad Core at 4GHz running vista. First, i rendered the scene
rad_def_test.pov, using the "Radiosity_OutdoorHQ" setting. As expected, 3.7
beta 31 was much faster that povray 3.6. But when i added the option
"recursion_limit 2", i get:

Povray 3.6: Total time 564 seconds.
Povray 3.7 beta 31, using all four cores: Total CPU time 12960.69 seconds, total
time 3335 seconds.

Yes, that is *23* times more CPU resources than Povray 3.6. and *6* times more
execution time. I im sure i used the same rendering settings in both versions:

512 x 384 +A0.3 +AM2 +R2.

The output images were identical.

Maybe this is a bug.

PS. This effect was observed in thread "Radiosity performance: thread count
anomaly". The original poster, clipka, showed a significant performance
difference between beta 29 and 30 when rendering the above scene with the
"2Bounce" setting, which practically sets the recursion_limit to 2. Somehow the
discussion took a different path, and also, the thread's title doesn't describe
the problem accurately, so i wrote this new post.

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