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From: lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall)
Newsgroups: comp.lang.perl
Subject: Re: what should length(@array) do ?
Message-ID: <10989@jpl-devvax.JPL.NASA.GOV>
Date: 10 Jan 91 18:47:03 GMT
References: <EMV.91Jan9211727@crane.aa.ox.com> <1991Jan10.063409.7185@iwarp.intel.com>
Reply-To: lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall)
Organization: Jet Propulsion Laboratory, Pasadena, CA
Lines: 53

In article <1991Jan10.063409.7185@iwarp.intel.com> merlyn@iwarp.intel.com (Randal L. Schwartz) writes:
: If you think that obody is huge, try something like:
: 
: body: {
: 	@obody = <STDIN>;
: 	$obodylen = 0;
: 	for (@obody) {
: 		$obodylen += length;
: 	}
: }
: 
: Yeah, actually, that's close to your solution.  You could also do it
: with a grep() (my formerly favorite operator, until I got tired of it
: :-) as in:
: 
: body: {
: 	@obody = <STDIN>;
: 	$obodylen = 0;
: 	grep($obodylen += length, @obody);
: }
: 
: which probably isn't any faster than the previous code.  (Larry?)

It's pretty much a dead heat.

I ran both five times on /etc/termcap and got.

Slurp + foreach:
2.3u 0.8s 0:10 29% 335+1119k 23+0io 30pf+0w
2.2u 0.6s 0:08 36% 220+1134k 22+0io 68pf+0w
2.4u 0.6s 0:06 44% 161+1128k 21+0io 5pf+0w
2.1u 0.8s 0:10 29% 163+1130k 23+0io 5pf+0w
2.3u 0.6s 0:06 43% 163+1164k 22+0io 5pf+0w

Slurp + grep:
2.3u 0.7s 0:06 51% 164+1164k 23+0io 6pf+0w
2.2u 0.7s 0:05 57% 161+1118k 23+0io 6pf+0w
2.3u 0.7s 0:05 55% 160+1101k 21+0io 5pf+0w
2.2u 0.7s 0:06 44% 161+1162k 23+0io 5pf+0w
2.1u 0.8s 0:06 44% 160+1115k 23+0io 5pf+0w

Now, just so you know what kind of overhead you pay for the slurp, here's
the original solution that just iterates over the lines and accumulates
lengths into a variable:
0.9u 0.2s 0:03 30% 206+134k 23+0io 63pf+0w
0.8u 0.1s 0:01 63% 157+137k 21+0io 5pf+0w
0.9u 0.2s 0:02 50% 159+139k 21+0io 5pf+0w
0.9u 0.1s 0:02 51% 156+138k 21+0io 5pf+0w
0.9u 0.1s 0:01 52% 157+139k 21+0io 5pf+0w

Moral: don't slurp files if you don't need to.

Larry