Cray divide speed
John D. McCalpin
mccalpin at masig3.masig3.ocean.fsu.edu
Mon Oct 30 09:40:54 AEST 1989
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 at masig1.ocean.fsu.edu
mccalpin at scri1.scri.fsu.edu
mccalpin at delocn.udel.edu
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