Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!uwvax!astroatc!johnw From: johnw@astroatc.UUCP (John F. Wardale) Newsgroups: comp.arch Subject: Re: What with these Vector's anyways? Message-ID: <363@astroatc.UUCP> Date: Mon, 20-Jul-87 22:10:50 EDT Article-I.D.: astroatc.363 Posted: Mon Jul 20 22:10:50 1987 Date-Received: Wed, 22-Jul-87 06:05:56 EDT References: <218@astra.necisa.oz> <142700010@tiger.UUCP> Reply-To: johnw@astroatc.UUCP (John F. Wardale) Organization: Astronautics Technology Cntr, Madison, WI Lines: 52 Summary: clarifications and nits In article <13401@topaz.rutgers.edu> ron@topaz.rutgers.edu (Ron Natalie) writes: >> Could someone out there explain to me what the basic idea is behind >> supercomputer CPU's? ...vectors...etc. Thanks Ron, for a generally Ecellent responce. Just a few additions: > Of course, you need to have >problems that using an array would be a speed up. This is the ability >to being "vectorized" that was referred to. The requirements are hard to explain, but just using arrays (in fortran or whatever is NOT enuf) The data values have to be know in time for the operators to operate on them. ARY (I) = some_function_of ARY (I-1) is *HARD* or impossible to vectorize. > ... SIMD (Single Instruction stream, Multiple Data stream) > ... Mulitiple Instruction and Multiple Data Streams (MIMD) don't forget SISD (single Instr. Single Data) (most common form) and MISD (in theory...I doubt any ever built one) >CRAY 2 - Similar to X-MP, newer and faster technology (a nit:) A Cray-2 is NOT like an XMP, but that's a different argumnent. Comments on Shared memory MIMD machines: This is probably the easiest and a fairly flexable solution. It works great for ~10 CPUs, but it you try it with ~100 CPUs, the memory get very overloaded (i.e. real-slow system-responce) The code it different programs can be o SCALAR (none of the following use SISD) o VECTORIZABLE (see above; use SIMD) o PARALLELIZABLE (well suited for MIMD machines) o Vec or Parr (use either) The problem is that most pograms contain sections that are each of the above classes. Each type machine will do best on different on different sections, and its usually the SCALAR portions that contribute to the LARGEST part of the run times. BTW: The Cray-1 & XMP are also very-good Scalar machines! John W - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Name: John F. Wardale UUCP: ... {seismo | harvard | ihnp4} !uwvax!astroatc!johnw arpa: astroatc!johnw@rsch.wisc.edu snail: 5800 Cottage Gr. Rd. ;;; Madison WI 53716 audio: 608-221-9001 eXt 110 To err is human, to really foul up world news requires the net!