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To: jimmey@lexis-nexis.com (Jimmey Todd) Subject: Re: Flex performance question In-reply-to: Your message of Thu, 19 Feb 1998 11:01:17 PST. Date: Thu, 19 Feb 1998 15:42:25 PST From: Vern Paxson <vern> So there are several problems. First, to go fast, you want to match as much text as possible, which your scanners don't in the case that what they're scanning is *not* a <RN> tag. So you want a rule like: [^<]+ Second, C++ scanners are particularly slow if they're interactive, which they are by default. Using -B speeds it up by a factor of 3-4 on my workstation. Third, C++ scanners that use the istream interface are slow, because of how poorly implemented istream's are. I built two versions of the following scanner: %% .*\n .* %% and the C version inhales a 2.5MB file on my workstation in 0.8 seconds. The C++ istream version, using -B, takes 3.8 seconds. Vern