Re: alex timings

From: Daan Sandee (
Date: Mon Feb 03 1992 - 10:46:16 CST

Okay, now I have what Alex provided you.
(a) He was running w/o opt, because the optimizer optimizes away the code.
(b) His output and my output for : CM2 16K, N=80000, SAXPY, differ by a
    factor of 100 in the printout. I *know* the program is wrong, so his
    output is actually correct. The mystery is, how he gets the right
    printout with the wrong program. Of course, he may have hand-corrected
    the output. Or, the version he sent you is not the latest one.
(c) So for a 16K CM2 he gets 20148.3135 MB/s which *I* compute to be
    5.622 bytes/PE/clock which is faster than the theoretical rate which *I*
    think is 4 bytes/PE/clock.
    (Those emphatic I's mean : feel free to have a different opinion).
(d) I still don't know
   (1) what you posted, because you are posting mflops, not transfer rates ;
     I compute 0.4685 flops/PE/clock or 1.679 GFlops.
   (2) what the Cray folks were complaining about.
(The bottom line, though, is that I still think the timer is screwed.
But I want to get the history straight before I get back to Alex.)

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