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Re: IEEE floating point support for guile?

From: Florian Weimer
Subject: Re: IEEE floating point support for guile?
Date: 11 Nov 2000 23:49:41 +0100
User-agent: Gnus/5.0808 (Gnus v5.8.8) Emacs/20.7

Chris Hanson <address@hidden> writes:

>    On GNU/Linux, the standard floating point round mode is "round to
>    extended precision" (64 bit, IIRC).  There is probably some code
>    out there which breaks when the rounding mode is changed that way.
>    If you want to embed Guile in your application, this can have quite
>    unexpected results.
> This isn't an accurate statement.  An accurate statement is that, on
> the x86 architecture, the default rounding mode is "round to nearest
> or even" and the default precision is "extended".  This is true not
> only for GNU/Linux on that platform, but for all other operating
> systems that I know of.  (Normally the operating system does not
> change the hardware default.)

On Win32, the operating system (or the MSVC runtime library) sets the
Precision Control Field (that's the official terminology, I think) to
53 bits -- at least this was done in the past.

> The problem with this as a default from the point of view of a
> cross-platform application like Guile is that this is _not_ the same
> default that is used on other hardware.

This is of course a problem.  On the other hand, Java, the only
language with strict requirements regarding identical floating point
behavior across all implementations, is regularly criticized because
of these requirements.

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