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Re^3: Efficient code.

by demerphq (Chancellor)
on Jan 30, 2006 at 18:23 UTC ( #526513=note: print w/replies, xml ) Need Help??

in reply to Re^2: Efficient code.
in thread Efficient code.

Juts FYI: In Perl 5.10 alternations not containing regex metachars will not backtrack at all as they are represented by a trie node that can traverse all of the alternations in a single pass. Id say which version of perl contains this but embarrasingly I appear to have forgotten.


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Re^4: Efficient code.
by Aristotle (Chancellor) on Jan 30, 2006 at 20:56 UTC


    Old geezer moment: sometimes these optimisations make me feel like I did when I was writing assembly code (inner loops of texture mappers slinging pixels… unrolling carefully, rejoicing when a clever trick got your loop down from 11 to 9 cycles per pixel – those were the days) and went from Pentium to PentiumPro – suddenly it was no longer possible to measure how many clock cycles any one instruction took: an innocuous change somewhere up or down the line would sometimes dramatically change the time response of an unrelated instruction, occasionally a loop iteration would randomly take more or less cycles than average, and sometimes instructions would appear to take a fractional amount of cycles. It was like wading through quicksand.

    Of course, there was no way to inspect the result of the PPro’s µ-Op translator. Thank goodness for use re 'debug'; :-)

    Makeshifts last the longest.

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