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Indeed you are correct, my original code is flawed as you describe. Thanks for pointing out my error Cees++

I've re-run a subset of the tests using the following slightly modfied version which corrects this error and the correction slows the insertion time by approximately 1 second for the million keys. The iteration time comes out exactly the same.

print time; $hash{ substr $_, 0, 4 } .= $/. $_ for 1 .. 1_000_000; $hash{$_} .= $/ for keys %hash; # Append a final separator print time; 1069484550 1069484566 # 16 seconds. $n=0; print time; for ( 1 .. 1_000_000 ) { # Ensure no partial matches by prepending and appending # separators to the search key. next unless exists $hash{ substr $_, 0, 4 } and 1+index( $hash{ substr $_, 0, 4 }, $/.$_.$/ ); $n++; } print time, $/, $n; 1069484612 1069484656 # 44 secs. 1000000

Examine what is said, not who speaks.
"Efficiency is intelligent laziness." -David Dunham
"Think for yourself!" - Abigail

In reply to Re: Re: A (memory) poor man's <strike>hash</strike> lookup table. by BrowserUk
in thread A (memory) poor man's <strike>hash</strike> lookup table. by BrowserUk

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