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Re: A prototype loop reverser for the scalarizer
- From: Toon Moene <toon at moene dot indiv dot nluug dot nl>
- To: Dorit Nuzman <DORIT at il dot ibm dot com>
- Cc: Daniel Berlin <dberlin at dberlin dot org>, fortran at gcc dot gnu dot org, Paul Thomas <paulthomas2 at wanadoo dot fr>, Sebastian Pop <sebastian dot pop at cri dot ensmp dot fr>, Steven Bosscher <stevenb dot gcc at gmail dot com>
- Date: Thu, 19 Oct 2006 21:55:50 +0200
- Subject: Re: A prototype loop reverser for the scalarizer
- Organization: Moene Computational Physics, Maartensdijk, The Netherlands
- References: <18311869.1161208207893.JavaMail.root@dtm1eusosrv72.dtm.ops.eu.uu.net> <4537CF5F.7060301@moene.indiv.nluug.nl>
Toon Moene wrote:
Hmmm, good idea, that -fassociative-math - why didn't I come up with
that myself ;-)
[ I suppose it means: treat (A+B)+C as the same as A+(B+C) ]
I realize this needs a correction:
In Fortran
A + B + C
means the processor (compiler, run time library, OS) can evaluate this
expression as either:
(A + B) + C
or
A + (B + C)
or
(A + C) + B
[Because the programmer didn't specify an order by applying parentheses]
This is what -fassociative-math should establish: It doesn't matter in
which order you add the terms, we don't care.
Cheers,
--
Toon Moene - e-mail: toon@moene.indiv.nluug.nl - phone: +31 346 214290
Saturnushof 14, 3738 XG Maartensdijk, The Netherlands
A maintainer of GNU Fortran: http://gcc.gnu.org/fortran/
Who's working on GNU Fortran:
http://gcc.gnu.org/ml/gcc/2006-01/msg00000.html