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From: O'KeefeHPS@sri-unix.UUCP
Newsgroups: net.lang.prolog
Subject: A Cautionary tale.
Message-ID: <1809@sri-arpa.UUCP>
Date: Thu, 12-Jul-84 02:49:25 EDT
Article-I.D.: sri-arpa.1809
Posted: Thu Jul 12 02:49:25 1984
Date-Received: Sat, 14-Jul-84 00:18:08 EDT
Lines: 21

From:  O'Keefe HPS (on ERCC DEC-10)

I just spent some time trying to make the tokeniser I recently
submitted to the Prolog library go faster.  I put in a table of
character codes in a way I know to be implementation dependent,
I unfolded calls in line, and generally got up to some tricks
I felt slightly ashamed of.  What was the result?
The new version ran 50% - 100% SLOWER.

On the subject of making things go faster, someone recently
sent in a list of versions of reverse that might go faster.
That issue seems to have been lost from our archive, but I
recall that the correspondent involved didn't give any
figures for how fast the different versions were.  I would
not be at all surprised if some or all of them were slower.

The really amusing thing here is that if I had tried to get
the most efficient program I could think of first, instead of
trying to get something to work and then optimising it, I would
have ended up with a slower program, and would have been quite
sure that t was as fast as I could make it.