Re (tilly) 5: how do I line-wrap while copying to stdout?

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Re:{6} how do I line-wrap while copying to stdout? by jeroenes (Priest) on Apr 20, 2001 at 18:36 UTC
By the undef $/, the file is read in as a huge string. Of course I checked, and with a n=1000 string I get: `Rate regex substr regex 21775/s -- -27% substr 29748/s 37% --` [download] Which makes sense, as my file has some 50k chars. Jeroen "We are not alone"(FZ) Update: (I'm not going to make a Re:{9} post) I'd say, start checking the source {grin} `$str='a'x1E6; => Rate regex substr regex 15.1/s -- -16% substr 18.0/s 19% -- $str='a'x1E7; => Rate regex substr regex 1.41/s -- -21% substr 1.79/s 27% --` [download] At 100M, I'm testing my swap ;-)..... I tried it nevertheless, but now I'm waiting for my box stop swapping... /me is afraid that may take a while... :-)... finally, I had to use that reboot button :-< 25M still went OK: `s/iter regex substr regex 1.80 -- -21% substr 1.42 27% --` [download] at 50M, benchmark produced a division by zero .....	[reply] [d/l] [select]
Re (tilly) 8: how do I line-wrap while copying to stdout? by tilly (Archbishop) on Apr 20, 2001 at 19:20 UTC
Oops, missed that. Still the principle that merlyn stated is correct, and is a common performance mistake in parsing. Try it with a 1 MB string. If substr still wins then I guarantee you that someone implemented a buffering strategy with strings and substr where doing a destructive substr at the beginning of a string just moves indexes around and does not recopy. Perl plays a lot of games like that, for instance that is why push, pop and friends are fast. I am just a little surprised to see it played on strings...	[reply]
(tye)Re2: how do I line-wrap while copying to stdout? by tye (Sage) on Apr 20, 2001 at 20:34 UTC
For proof that destructive substr() at the begining of a string doesn't move stuff, see (tye)Re: Creative use of pack/unpack - tye (but my friends call me "Tye")	[reply]