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Floating point results change with different compilation options
- From: "Cristea Bogdan" <cristeab at gmail dot com>
- To: gcc-help at gcc dot gnu dot org
- Date: Tue, 23 Oct 2007 10:04:35 +0200
- Subject: Floating point results change with different compilation options
Hi
I use gcc compiler in order to study the behavior of some iterative
maps (x_n=f(x_{n-1})) using single floating point precision (following
IEEE 754 standard). I have noticed that using different compiler
options, the output sequence could be very different. My programs are
written in C++ using 'float' type and I use 'gcc version 4.1.2
20061115 (prerelease) (Debian 4.1.1-21)'. Compilation options are:
'-Wall -O3 -march=pentium4' or '-Wall'. The same program compiled with
gcc 4.2.2 gives the same results regardless of the compilation options
(on an athlon64 processor).
Is this a bug of the compiler or the floating point representation
differs from one compiler version to the other?
--
Bogdan Cristea