Date: Mon, 10 May 1999 20:22:40 +0200
To: pgcc AT delorie DOT com
Cc: David Whysong <dwhysong AT physics DOT ucsb DOT edu>
Subject: Re: Optimization question
Message-ID: <19990510202240.F10032@cerebro.laendle>
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	David Whysong <dwhysong AT physics DOT ucsb DOT edu>
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In-Reply-To: <Pine.SOL.3.96.990510125208.12696D-100000@ursa.cus.cam.ac.uk>; from Dr H. T. Leung on Mon, May 10, 1999 at 01:07:16PM +0100
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From: Marc Lehmann <pcg AT goof DOT com>
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On Mon, May 10, 1999 at 01:07:16PM +0100, Dr H. T. Leung wrote:
> If you had read the mailing list archive, it is terribly unfair to people
> on the list to cc you replies when you are not on the list. If you want to
> ask a question, subscribe, read on for a while, then post (then maybe
> unsubscribe). 

Well, the official policy is to state that you are not on the the list
and just post your question. I don't think his particular posting was too
annoying, do you?

> very simple example, You were doing multipication "Pv1*v01" 4 times; that
> means retrieves 2 values from memory, multiply, store it back, done 4

No, it doesn't. This only puts more pressure on the optimizer, but the
examples it cannot handle are much more complicated.

> defining new variables like this and break down your calculation so that
> it doesn't re-do little multiplications like this;

This is useless for simple cases. It helps for difficult cases where the
compiler cannot optimize for aliasing or similar reasons .

--  
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