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Re: Re: Up for Critique

by biograd (Friar)
on Mar 23, 2002 at 06:43 UTC ( #153737=note: print w/ replies, xml ) Need Help??


in reply to Re: Up for Critique
in thread Up for Critique

There were a couple reasons I went for the wholesome all-array approach...one of them is I have just never been as comfortable with hashes as I have been with arrays. This is no excuse, of course, and I've been meaning to use them more. I just always see the array algorithm first. (Can you tell I'm new???) Second, I'd read in Mastering Algorithms with Perl about the speed of arrays over hashes, so I felt justified. (Webadept noted this below too.)

However, I can see the utility of hashes from many of these examples, yours and others below, so I know I'll have to bite this bullet soon. Thanks for the example, tested or not. :)

-Jenn


Comment on Re: Re: Up for Critique
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(jeffa) 3Re: Up for Critique
by jeffa (Bishop) on Mar 23, 2002 at 17:31 UTC
    Speed vs. Maintainability/Scalability

    If the difference in speed is small, i say drop the arrays and use hashes ... but i am lazy. I have this adversion to something called 'typing'. ;)

    But, arrays are not always faster than hashes. It all depends upon context - if you have to scan the entire array to find something, a hash implementation will probably be faster. But if you have to iterate over all elements - then an array is probably the better choice. Consider the following Benchmark code:

    use strict; use Benchmark; my %h; my @a = ('a'..'zzz'); @h{@a} = (1) x @a; timethese('-10', { find_array => sub { return (grep /^ccc$/, @a) ? 1 : 0 }, find_hash => sub { return $h{'ccc'} }, iterate_array => sub { do {} for @a }, iterate_hash => sub { do {} for keys %h }, }); __END__ yields on my dual proc 400 linux box: (YMWV) find_array: 10 wallclock secs (10.11usr + 0.04sys = 10.15 CPU) @ 45.62/s (n=463) find_hash: 13 wallclock secs (11.41usr + 0.07sys = 11.48 CPU) @ 1183591.72/s (n=1 +3587633) iterate_array: 11 wallclock secs (10.98usr + 0.09sys = 11.07 CPU) @ 70.28/s (n=778) iterate_hash: 11 wallclock secs (10.78usr + 0.05sys = 10.83 CPU) @ 16.53/s (n=179)

    jeffa

    L-LL-L--L-LL-L--L-LL-L--
    -R--R-RR-R--R-RR-R--R-RR
    B--B--B--B--B--B--B--B--
    H---H---H---H---H---H---
    (the triplet paradiddle with high-hat)
    

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