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From: djh@xipe.osc.edu (David Heisterberg)
Newsgroups: comp.lang.fortran
Subject: Re: Cray memory stride (was Re: vectorization question reposed)
Message-ID: <1512@sunc.osc.edu>
Date: 31 Mar 91 14:23:48 GMT
References: <1991Mar30.142903.5225@ariel.unm.edu> <27758@uflorida.cis.ufl.EDU>
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In article <27758@uflorida.cis.ufl.EDU> bernhold@red (David E. Bernholdt) writes
>I asked this question a while ago.  I _think_ that the (two) YMPs to
>which I have access have 256 banks.
>...
>Once you've got the number of banks, the most general thing to do is
>to work with vectors who's length is prime relative to the number of
>banks.

For single stream performance it is the number of sub-sections rather
than banks that is important.  A memory reference makes a particular
bank unavailable to all CPUs, and the containing sub-section unavailable
to further references from the same CPU, for 5 CP.  I lack a definative
statement, but I think all YMPs have 32 sub-sections.  The 2 series has
64 banks; the 4, 128; and the 8, 256.
--
David J. Heisterberg		djh@osc.edu		And you all know
The Ohio Supercomputer Center	djh@ohstpy.bitnet	security Is mortals'
Columbus, Ohio  43212		ohstpy::djh		chiefest enemy.