NetNews Usenet Archive 1992 #18/NN_1992_18.iso/spool/comp/lang/pascal/4841

Internet Message Format | 1992-08-13 | 1.6 KB

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From: [e-mail] (|S| Norbert Juffa)
Newsgroups: comp.lang.pascal
Subject: Re: Why are set operations so Slow?
Date: 13 Aug 1992 17:48:18 GMT
Organization: University of Karlsruhe (FRG) - Informatik Rechnerabt.
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In-Reply-To: [e-mail]'s message of Wed, 12 Aug 1992 14:15:13 GMT

In <[e-mail]> [e-mail] writes:

> The claim I saw in the Stoney Brook pamphlet was that operations on sets
> were converted to the equivalent bitwise operations when possible.  If S is
> a set of 250..255, then S+[251] would be compiled to do a bitwise OR of 2
> into S.  That's not a choice that was available to you in improving the RTL;
> you'd have to go back further, and change the code generator.
>
Well, it just occured to me that most of the info TP passes to the library
routines for set handling is know at compile time. So the code generator
could precompute the offset into the byte array representing the set and
the appropriate bit mask to greatly speed up most set operations, at least
if constants are involved somewhere.

Norbert
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Norbert Juffa        email: [e-mail]        Live and let live!