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Re^3: Bidirectional lookup algorithm? (no redis )

by polettix (Vicar)
on Jan 10, 2015 at 22:15 UTC ( [id://1112874]=note: print w/replies, xml ) Need Help??


in reply to Re^2: Bidirectional lookup algorithm? (no redis )
in thread Bidirectional lookup algorithm? (Updated: further info.)

Although in the OP there were no specific quality parameters about space/time constraints, my understanding is that space efficiency improvements could come at the expense of (some) speed, hence the suggestion.

Any benchmark should probably consider both aspects.

perl -ple'$_=reverse' <<<ti.xittelop@oivalf

Io ho capito... ma tu che hai detto?
  • Comment on Re^3: Bidirectional lookup algorithm? (no redis )

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Re^4: Bidirectional lookup algorithm? (no redis )
by BrowserUk (Patriarch) on Jan 10, 2015 at 23:07 UTC
    my understanding is that space efficiency improvements could come at the expense of (some) speed,

    You are correct in that. The ultimate desire is to retain (as much of as is possible) the speed of Perl's hashes; whilst reducing the space requirement necessitated by the need for bidi lookup.

    My initial brief suggested that a move from O(1) to O(logN) (with a very small constant) lookup time would be acceptable; if a 4:1 (75%) reduction in space/1:4 (400%) increase in capacity (or greater) was achieved.

    However, anonymonk is also correct, in that external storage -- whether disk/SSD or remote ram via sockets -- is too slow. A simple test will show that the minimum turnaround time of sending a request to a 'remote' (even where 'remote' equates to the callback address) and retrieving the reply requires 3 times as long as a perl hash loopkup. Even when you completely exclude the actual lookup and have the request and response consist of a single byte each way.

    No matter how fast the actual lookup at the remote, adding that constant to it crushes the overall goal.


    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.
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      I see. So, more or less you're left with the thing you were after in the first place - the algorithm. Good luck with that!

      perl -ple'$_=reverse' <<<ti.xittelop@oivalf

      Io ho capito... ma tu che hai detto?

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