Date: Tue, 5 Apr 2005 23:20:43 -0700 From: Brooks Davis <brooks@one-eyed-alien.net> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Jeremie Le Hen <jeremie@le-hen.org> Subject: Re: strcspn(3) complexity improvement Message-ID: <20050406062043.GB22691@odin.ac.hmc.edu> In-Reply-To: <200504060346.j363ko4b088610@apollo.backplane.com> References: <20050330083435.GI75546@obiwan.tataz.chchile.org> <20050330110613.GB71384@cirb503493.alcatel.com.au> <20050330183145.GB24465@odin.ac.hmc.edu> <200504060346.j363ko4b088610@apollo.backplane.com>
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--p4qYPpj5QlsIQJ0K Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Apr 05, 2005 at 08:46:50PM -0700, Matthew Dillon wrote: > :The real question I have is, how long does the string need to be before > :this is a win and how much does it hurt for typical string lengths? > :I've written code with strcspn that needed to perform well, but it was > :parsing 80-column punch card derived formats. >=20 > I think the answer is to not use strcspn() in cases where it *really* > matters. Certainly. strcspn() wasn't worth optimizing out after I replaced the hand coded crap that used getc to parse files up to 100MB is size and did a realloc for each character! That got me a 50% speedup in overall execution time and the function dropped from #1 to <#50 in the profiling numbers. At that point FPU intensive code was at the top where it belonged. My main point was to avoid a purely theoretical "optimization". -- Brooks --=20 Any statement of the form "X is the one, true Y" is FALSE. PGP fingerprint 655D 519C 26A7 82E7 2529 9BF0 5D8E 8BE9 F238 1AD4 --p4qYPpj5QlsIQJ0K Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQFCU3+yXY6L6fI4GtQRAo3cAKCjGIbjiZbYPuBrUDMBmlq8s9UbqgCaAj8u PMXZq4cqToA2dCnZ7RUy2E0= =fV/5 -----END PGP SIGNATURE----- --p4qYPpj5QlsIQJ0K--
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