• Read about logic and USL...

    From Ramine@21:1/5 to All on Tue Apr 26 15:16:35 2016

    Please download here the free book about USL methodology from Baron


    You can read clearly inside the book this:

    "To forecast scalability beyond what’s observable, be pessimistic and
    treat the USL as a best-case scenario that won’t really happen. Use
    Equation 4 to forecast the maximum possible throughput, but don’t
    forecast too far out. Use Equation 6 to forecast response time."

    As you have noticed he is not saying "don't forecast", he
    is saying clearly: "don’t forecast too far out", that means
    that you can forecast not too far out. And that's illogical,
    simply because, in a parallel program, a locked region using
    locks can escape contention at fewer cores and fewer threads
    and can than hit the contention at more cores and more threads..
    so you can not use nonlinear regression to predict scalability,
    so why Baron Schwartz is saying: "don’t forecast too far out",
    so i mean why then forecast, since you can not predict scalability ?
    that's like illogical from Baron Schwartz ! so what is the purpose
    of the USL methodology that uses nonlinear regression? its purpose
    is to permit us to test and see how much there is contention and how
    much there is crosstalk(cache misses etc..), that's all, it's not a tool
    to predict scalability.

    Thank you,
    Amine Moulay Ramdane.

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