Re: -ffast-math option at compling octave in FreeBSD ports ?

[Thomas Weber]

On Sun, Dec 07, 2008 at 05:12:29PM +0900, Tatsuro MATSUOKA wrote:
> Hello
> 
> In an octave thread in Japan, there was a report that asked the meaning 
> -ffast-math option in FreeBSD ports.
> 
> It will be glad for me if there are some peple who will give me information 
> about it.

It tries to exploit some processor features for faster mathematic
functions, but breaks IEEE 754 for that. Citing gcc's manual:

========================================================================
This option causes the preprocessor macro __FAST_MATH__ to be defined.
This option is not turned on by any `-O' option since it can result in
incorrect output for programs which depend on an exact implementation of
IEEE or ISO rules/specifications for math functions. It may, however,
yield faster code for programs that do not require the guarantees of
these specifications.
========================================================================

For details, you are probably best off asking on gcc's list.

The obvious question is now whether Octave and all used libraries work
with -ffast-math. Sorry, I have no idea about that.

        Thomas