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From: lindsay@gandalf.cs.cmu.edu (Donald Lindsay)
Newsgroups: comp.sys.super,comp.arch
Subject: Re: Massively Parallel LINPACK on the Intel Touchstone Delta machine
Message-ID: <13301@pt.cs.cmu.edu>
Date: 6 Jun 91 04:22:37 GMT
References: <1991Jun3.130104.15667@hubcap.clemson.edu> <1991Jun3.233741.8570@elroy.jpl.nasa.gov>
Organization: Carnegie Mellon
Lines: 27

In article <1991Jun3.233741.8570@elroy.jpl.nasa.gov> 
	stevo@elroy.jpl.nasa.gov (Steve Groom) writes:
>Can someone explain how "massively parallel LINPACK" is different from
>regular LINPACK?

Dongarra's latest Linpack report states that a fixed-size problem is
inappropriate for a scalable ensemble machine. So, instead, the
matrix size is allowed to vary. The solution method is considered
irrelevant: FLOPS is defined as  (2/3 N^3 + 2 N^2) / elapsed-time.

The Linpack reports wants the following numbers:
 - Accuracy residual.
 - GFLOPS and N for the largest problem run.
 - N-HALF, the problem size that achieved half the GFLOPS.
 - Theoretical peak GFLOPS.
 - Number of processors.

In the following, it's interesting to see the ratio of N^2 to N-HALF^2:

N	N-HALF	  ratio
------	------    -----
26,624	11,000	    6		CM-2	   64 K PE (or, 2 K FPU)
21,376	 3,193	   45		nCUBE 2	    1 K PE
 5,504   1,180     22		MasPar	   16 K PE
14,000	 5,500?     6		Touchstone, 512 PE, as just reported
-- 
Don		D.C.Lindsay 	Carnegie Mellon Robotics Institute