in reply to Re^6: PDL: Looking for efficient way to extract sub-images, by finding bounding boxes of "objects" (7000x faster)
in thread PDL: Looking for efficient way to extract sub-images, by finding bounding boxes of "objects"

If this difference in performance between versions was due to optimisations of the internals between those versions, then:

  1. Wouldn't you expect it to apply pretty evenly to all the subroutines rather than just one of them?
  2. If they'd succeeded in making Perl run 135x faster, I'm pretty sure we'd all have heard about it.

The idea I had about a possible cause of the pathological behaviour of yr() code is my memory of this Windows memory allocation bug What could cause excessive page faults? that I discovered 7 years ago that, under some very specific circumstances, caused the CRT code underlying Perl to generate millions of page faults. But that is not the cause here.

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