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

by dbuckhal (Friar)
on Nov 22, 2016 at 03:51 UTC ( #1176303=note: print w/replies, xml ) Need Help??


in reply to Re^5: 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"

(*I have an idea about the cause of the slowness in 5.10; I'll need to think of a way to verify it.)
I came across this article a little while back. It might help explain the speed difference. I certain have seen a difference running a Perl application between 5.1x and 5.22.

How We Spent Two Days Making Perl Faster

Hope you find it interesting!
  • Comment on Re^6: PDL: Looking for efficient way to extract sub-images, by finding bounding boxes of "objects" (7000x faster)

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Re^7: PDL: Looking for efficient way to extract sub-images, by finding bounding boxes of "objects" (7000x faster)
by BrowserUk (Pope) on Nov 22, 2016 at 08:39 UTC

    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.


    With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority". The enemy of (IT) success is complexity.
    In the absence of evidence, opinion is indistinguishable from prejudice.

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