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Re^6: Memory Efficient Alternatives to Hash of Array

by BrowserUk (Pope)
on Dec 28, 2008 at 01:05 UTC ( #732852=note: print w/replies, xml ) Need Help??


in reply to Re^5: Memory Efficient Alternatives to Hash of Array
in thread Memory Efficient Alternatives to Hash of Array

I stand corrected.

However, you're still better off using an external sort, as it allows you to gather the multiple values for each key together without loading the entire dataset into memory. Using a fairly simple loop like this:

#! perl use strict; my( $key, @array ) = split "\t", <>; while( <> ) { chomp; my( $newKey, $value ) = split "\t"; if( $newKey eq $key ) { push @array, $value; next; } else { # Process @array for $key #... ## Remember the newKey $key = $nextKey; ## And the reset the array @array = $value; } }

And a command line like:

sort < unsortedFile | perl theScriptAbove

Or just sort the file and then feed it to the script as separate steps:

sort < unsortedFile > sortedFile perl theScriptAbove sortedFile

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".
In the absence of evidence, opinion is indistinguishable from prejudice.

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Re^7: Memory Efficient Alternatives to Hash of Array
by tilly (Archbishop) on Dec 28, 2008 at 02:30 UTC
    *ahem* My first answer had the same idea, but with one less bug.

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