Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!gatech!hubcap!Ray From: Ray@hubcap.UUCP Newsgroups: comp.hypercube Subject: Re: communications intensive applications Message-ID: <304@hubcap.UUCP> Date: Thu, 16-Jul-87 09:00:41 EDT Article-I.D.: hubcap.304 Posted: Thu Jul 16 09:00:41 1987 Date-Received: Sat, 18-Jul-87 06:40:57 EDT Sender: fpst@hubcap.UUCP Lines: 40 Approved: hypercube@hubcap.clemson.edu In article <270@hubcap.UUCP> fpst@hubcap.UUCP (Dennis Stevenson) writes: > >One such 'application' that may be interesting was described in the >April 1987 edition of IEEE Computer. "Multiprocessing the Sieve of >Eratosthenes" by S.H.Bokhari. This uses a FLEX-32 shared memory >machine to implement a novel prime number sieve benchmark. > We have implemented the "Seive of Erathosthenes" on the Intel Hypercube as follows: The tablet of N numbers is divided evenly amongst the p processors (p can be any value up to the maximum number of processors in the configuration). Processor 0 contains the first N/p numbers, 1 contains the next, etc. Processor zero is in charge and will have all of the SQRT(N) first primes. Zero finds the prime and before sieving broadcasts the value to all participating processors. Each processor (including zero) then strikes out those multiples of the prime which belong to him. Once zero has finished striking, he finds the next prime and broadcasts it, etc. Each processor has an equivalent number of numbers and they all seive with the same prime at the same time. The work is balanced. Once zero has found the first SQRT(N) primes, seiving is finished and each processor can search through his subset of numbers and report the primes, again a perfectly balanced computation. This code has been implemented in FORTRAN and runs on an iPSC */MX (* = 4,5 or 6). -- Ray Asbury CSNET: ray@isc.intel.com Intel Scientific Computers 15201 NW Greenbrier Parkway Beaverton, Oregon 97006 (503) 629-7641