Cray divide speed

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Article #2884

#2884

From: John D. McCalpin
Date: Sun, 29 Oct 1989 22:40

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Does anyone have the figures handy for the peak speed of the Cray
X/MP, the Cray Y/MP, and the Cray 2 for vector divide operations?

I know that Cray uses an approximate reciprocal scheme, but I need to
know how many cycles per result are required for a plain vector
divide, i.e.

	DO 100 I=1,N
	    A(I) = B(I)/C(I)
  100	CONTINUE

On the Cyber 205 and ETA-10, the number is 6 cycles per element, and I
am trying to figure out if that is a representative number for vector
machines. I am using this information to modify the work estimates for
various implicit and explicit finite-difference schemes used in fluid
dynamics.
--
John D. McCalpin - mccalpin@masig1.ocean.fsu.edu
		   mccalpin@scri1.scri.fsu.edu
		   mccalpin@delocn.udel.edu

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From: mccalpin@masig3.masig3.ocean.fsu.edu (John D. McCalpin)
Newsgroups: comp.arch,comp.sys.super,comp.unix.cray
Subject: Cray divide speed
Message-ID: <MCCALPIN.89Oct29174054@masig3.masig3.ocean.fsu.edu>
Date: 29 Oct 89 22:40:54 GMT
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