Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!tank!uxc!uxc.cso.uiuc.edu!m.cs.uiuc.edu!wsmith
From: wsmith@m.cs.uiuc.edu
Newsgroups: comp.arch
Subject: Re: String lengths
Message-ID: <3300052@m.cs.uiuc.edu>
Date: 7 Feb 89 04:23:00 GMT
References: <762@atanasoff.cs.iastate.edu>
Lines: 16
Nf-ID: #R:atanasoff.cs.iastate.edu:762:m.cs.uiuc.edu:3300052:000:686
Nf-From: m.cs.uiuc.edu!wsmith    Feb  6 22:23:00 1989


On using machine string instructions for performing things such
as index() that need the length of the string ahead of time...

On the 80x86 family of chips, I believe it is possible for a routine to 
beat the fancy string instructions with clever coding that does not need
the length of the string so that the index() subroutine does not average 
O(length), but instead much less than that when the pattern is near the 
beginning.   Certainly on some of the low end VAXes this was true also 
because the special string instructions were executed by software.
Just because they give a special instruction, doesn't mean you have to 
use it.

Bill Smith
wsmith@cs.uiuc.edu
uiucdcs!wsmith