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Re: Expression and Meta Templates Problem using C++ (Wrong results)

From: Jim Wilson <wilson at specifixinc dot com>
To: Olaf Petzold <opetzold at wit dot regiocom dot net>
Cc: gcc at gcc dot gnu dot org
Date: Mon, 15 Sep 2003 19:58:33 -0700
Subject: Re: Expression and Meta Templates Problem using C++ (Wrong results)
References: <002201c37b69$5cd1ed30$6802a8c0@wit.regiocom.net>

Olaf Petzold wrote:

matrix-matrix product. The problem is related to the temporary temp_lhs used
by the prod function. If I make the temp static I've got right results but,
other/further matrix multiplications calculate wrong results (same
dimensions with other values using the same static temp).

Try submitting a bug report. See http://gcc.gnu.org/bugs.html.

There are known x86 FP problems with gcc. This is partly gcc's fault, and partly the fault of the x86 FPU. They are collectively refered to as the excess precision problem. If the problem only shows up on x86, then this could be the case. Or it could be a compiler bug.

There is some info about the excess precision problem in this thread
    http://gcc.gnu.org/ml/gcc/2003-08/msg01195.html
--
Jim Wilson, GNU Tools Support, http://www.SpecifixInc.com

References:
- Expression and Meta Templates Problem using C++ (Wrong results)
  - From: Olaf Petzold

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