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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 16:18:53 +0100
User-agent: Gnus/5.0808 (Gnus v5.8.8) Emacs/20.7

Jim Blandy <address@hidden> writes:

> - By default, Guile should use the standard IEEE double-precision
>   format for all flonum values and intermediate values.  On the IA-32,
>   this implies changing the FPU's precision control field to "double
>   precision (53-bits)".

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.

(I'm extrapolating from reports regarding the Win32 platform, where
some graphics drivers unconditionally set the precision to 53 bits,
even if an application changed it.  Some code assumed that the FPU was
in the mode set at program startup and failed quite miserably.)

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