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RE: Linux doubles precision bug?
- From: "Betty Evans" <bevans at ittvis dot com>
- To: "Ian Lance Taylor" <iant at google dot com>
- Cc: <libstdc++ at gcc dot gnu dot org>
- Date: Wed, 27 Feb 2008 08:53:33 -0700
- Subject: RE: Linux doubles precision bug?
Ian
Thank you so much for your reply. I also received good advise from
Phillip Jordan. He noted that the -ffloat-store option would solve my
problem but that there is an performance hit using this compiler option.
Betty
-----Original Message-----
From: Ian Lance Taylor [mailto:iant@google.com]
Sent: Tuesday, February 26, 2008 3:58 PM
To: Betty Evans
Cc: libstdc++@gcc.gnu.org
Subject: Re: Linux doubles precision bug?
"Betty Evans" <bevans@ittvis.com> writes:
> Running the same code gives me different results on Linux 32 bit and
64
> bit computers. I'm not sure if it is a bug or not but other compilers
> give the same results when run on 32 and 64-bit systems.
This question would be better directed to the mailing list
gcc-help@gcc.gnu.org. Please take any followups there. Thanks.
You didn't mention the processor, but let's assume it's x86. On x86,
32-bit floating point code uses the x87 registers with 80-bit
precision. 64-bit floating point code uses the SSE registers with
64-bit precision. Different results are normal and expected.
You may find it interesting to look at http://gcc.gnu.org/PR323 .
Ian