Re: math function accuracy -- was Re: text2interval again /
On 2013-03-12 17:01:19 +0000, John Pryce wrote:
> Folk
You forgot to put the list in Cc. Fixing that...
> On 12 Mar 2013, at 16:08, Vincent Lefevre wrote:
> > On 2013-03-12 10:30:12 -0500, Ralph Baker Kearfott wrote:
> >> Is this argument meant to help us come to a consensus on
> >> what accuracy (if any) we are to demand of the end points
> >> of enclosing intervals for the elementary functions in
> >> P-1788, i.e. what should be in the second column of
> >> Table 8, p. 43 of the draft John just passed around.
> >> Are we saying the "accurate" requirement for "sin" might
> >> be too strict?
> >
> > Perhaps, in particular because of the fact that the rounding direction
> > is not necessarily honored mainly the math functions. But it may also
> > not be available, e.g. in case of static rounding modes, in which case
> > the arithmetic operations (+, -, *, /, sqrt) are affected too.
> >
> > So, the only requirements could be containment ("valid" accuracy mode)
> > and other accuracy modes could be recommendations.
> I am in favour of that.
>
> > But for 754-conforming P1788 implementations, you can add the
> > associated "tightest" requirements for each supported function
> > (this includes the required functions +, -, *, /, etc.).
> Why treat this separately? Just note, as part of the
> recommendations, that it is straightforward to get "tightest" for
> these functions in a 754-conforming implementation. As Bill reminds
> us, QoI gives the needed incentive.
It is not necessarily straightforward, e.g. if the implementation
doesn't want to change the rounding mode. But I thought that this
was the purpose of a 754-conforming implementation to have such
requirements. Otherwise, what's the point of this notion?
--
Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)