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Re: I vote NO on Motion P1788/M0024.02:RoundedOperations

Dan,

the motion does not "require explicit hardware instructions for directed rounding operations"!

It just requires the arithmetic operations with directed roundings. I learned that in these IEEE standards documents there is a difference between shall and should. In the motion they are used that way.

I attach a short article which might be interesting for one or the other.

Best wishes
Ulrich


Am 13.05.2011 16:40, schrieb Dan Zuras Intervals: 
	Folks,

	I vote NO on Prof Kulish's motion to require a
	conforming implementation to provide explicit
	hardware instructions for directed rounding
	operations.

	There are many reasons.

	We are an arithmetic standards body not a hardware
	standards body.  It is not our place to dictate
	how our implementers shall design their hardware.

	Also, to do so would eliminate nearly all existing
	hardware from any possibility of conforming to our
	standard.  This would severely limit acceptance of
	1788 in the market.

	We have already gone out of our way to provide for
	the flexibility necessary to eliminate the need for
	frequent changes in rounding mode.  For example,
	permitting representations of the form [-inf,sup]
	rather than [inf,sup].  Thus, much of the performance
	improvement Prof Kulish seeks can already be had on
	existing hardware without new instructions.

	All of that having been said, what Prof Kulish
	suggests would clearly be a good idea for any
	architecture that permits it.  Indeed, some already
	have such instructions.  But it is up to the hardware
	designers to decide what is best for their customers,
	not us.

	Perhaps someday hardware designers will include even
	more useful instructions than explicit directed
	rounding instructions.  If 1788 is successful we may
	even see explicit interval registers with explicit
	interval add, subtract, et al.

	But not today.

	And not by our demanding it of them.

	That's how I feel anyway.

	Yours,

				Dan




-- 
Karlsruher Institut für Technologie (KIT)
Institut für Angewandte und Numerische Mathematik (IANM2)
D-76128 Karlsruhe, Germany
Prof. Ulrich Kulisch

Telefon: +49 721 608-42680
Fax: +49 721 608-46679
E-Mail: ulrich.kulisch@xxxxxxx
www.kit.edu
www.math.kit.edu/ianm2/~kulisch/

KIT - Universität des Landes Baden-Württemberg und nationales Großforschungszentrum in der Helmholtz-Gemeinschaft

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