From: hjstein@bfr.co.il (Harvey J. Stein) Newsgroups: comp.lang.fortran,comp.parallel.pvm Subject: Re: superlinear speedup, (was: fortran77 programming) Date: 14 Dec 1998 12:09:38 +0200 Organization: Unspecified Organization Message-Id: References: <3660D892.E1EDBF12@est.it> <3665044D.A0F57E59@kings.uq.edu.au> <3665E491.7993355@flash.net> <366BF6F3.1E8DC934@cic-mail.lanl.gov> Cc: hjstein@bfr.co.il Xref: ukc comp.lang.fortran:62155 comp.parallel.pvm:7868 "Tony T. Warnock" writes: > A simple argument (due to Vance Faber of LANL) shows that > superlinear speedup is not possible. Given an N times faster > processor, one can have the processor execute the first instruction > of each of the N slower processors, then the second instruction, > etc. The faster processor will finish at least as fast as the > slower set of processors. One can't do this and it'd make a modern processor slower. One can't do it because the the registers will be in the wrong state Even if you could do it, it'd make a modern processor slower because you'd break pipeline optimizations that had been done to the individual programs. -- Harvey J. Stein BFM Financial Research hjstein@bfr.co.il