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Re: Fourth Draft "Unsafe fp optimizations" project description.


On Mon, 13 Aug 2001 dewar@gnat.com wrote:

> <<They are as "accurate" - it's just that they have a more limited
> argument range.
> >>
> 
> I do not believe that these built in routines meet the Ada requirements
> for accuracy. At least I cannot prove that from the documentation Intel
> provides.
> 

Look in an appendix of the original Pentium documentation, where they
compare the accuracy of the transcendental instructions to the VAX H float
(128-bit) library and discuss the differences with earlier processors.

I can send you a copy if Intel has cleaned up its web site. I don't have
the Ada requirements but I can't believe that anybody could seriously ask
for more accuracy (you never know until you read, however). The behaviour
on out-of-range inputs is another matter, although I believe that anybody
calling direct trigonometric functions (sin, cos and especially tan) with
large arguments should be aware of the risks he/she is taking.

	Regards,
	Gabriel.



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