Author: Sune Fischer
Date: 09:16:48 10/02/01
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Hi Just curious, does anyone know of a parallel algorithm which is faster than the serial one, for any type of problem? I know of many that can be done equally fast (in theory) at 2x half the power, for example vector operations. Fortran 90 (and above) has some great support for that. I have never ever heard of a parallel algorithm that was faster than the serial one (on 1 CPU of cause). It seems the communication and coordination between threads plus the increased complexity will always cost you performance. I'm pretty sure one can design a formal proof, using... minimal entropy principles?? The timeslicing argument/proof is good enough for me though. Even if such an algorithm existed, which I seriously doubt, then I don't believe it would run >2x faster on a dual 1 Gig than on a single 1 Gig chip. I have tried myself parallizing a FFT algorithm to about a 95% effciency, it ran only 23% faster (dual celerons on an Abit BP6 mobo). I conclude there were other bottlenecks, and most likely there will be on most PC-systems for a long time to come. The BUS is not fast enough to supply two chips whith data all the time, it can hardly keep up with 1 chip as it is. That of cause is a different story, and may change in the future. -S.
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