mbutts@mentor.com (Mike Butts) (12/15/89)
> In article <112400013@uxa.cso.uiuc.edu> afgg6490@uxa.cso.uiuc.edu writes: >> >>..> Reciprocal approximation > > [list of machines that use NR approx to do divides...] > All Floating Point Systems 64-bit machines (164, 264, M64-xxx) use reciprocal approximation, as does the Mentor Graphics Compute Engine. I recall being told (years ago, now) by algorithmic folks that much work in scientific computing over the years has been directed towards finding algorithms that minimize the need for division, because it is so much more expensive (in time and/or HW) than multiplication. Given the existence of such, architects of scientific CPUs found reciprocal lookup tables to be far preferable to FP divide hardware in speed and simplicity. -- Michael Butts, Research Engineer KC7IT 503-626-1302 Mentor Graphics Corp., 8500 SW Creekside Place, Beaverton, OR 97005 !{sequent,tessi,apollo}!mntgfx!mbutts mbutts@pdx.MENTOR.COM Opinions are my own, not necessarily those of Mentor Graphics Corp.
khb@chiba.sun-bb (Keith Bierman - SPD Advanced Languages) (12/16/89)
In article <1989Dec14.184714.1473@mentor.com> mbutts@mentor.com (Mike Butts) writes:
I recall being told (years ago, now) by algorithmic folks that much work in
scientific computing over the years has been directed towards
finding
This generally resulted in algorithms with numerical problems. Most
really stable algorithms wind up with some divides and sqrts. That is
why many RISC machines have these instructions.
--
Keith H. Bierman |*My thoughts are my own. !! kbierman@sun.com
It's Not My Fault | MTS --Only my work belongs to Sun*
I Voted for Bill & | Advanced Languages/Floating Point Group
Opus | "When the going gets Weird .. the Weird turn PRO"
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