[RC5] Speed

Dan Sugalski sugalskd at osshe.edu
Mon Apr 20 20:39:25 EDT 1998


On Mon, 20 Apr 1998, Bojan Baros wrote:
> On Mon, 20 Apr 1998, Dan Sugalski wrote:
> 
> > At 11:35 AM 4/20/1998 -0400, Bojan Baros wrote:
> > >Some of you will remember that a month or so ago I asked the question of 
> > >Flops that D.Net has.  I got my answer today.  Combined MFlops are : 
> > >2959855 or at least that is what it says on the stats page (thumbs up for 
> > >new look).  That I think officially makes us the fastest computer on the 
> > >net.
> > >	Also, is it possible that someone from the admin write a letter to 
> > >the magazine byte and tell them that they are wrong (the said that 
> > >fastest computer has broken 1 terraflops).
> > 
> > Except, of course, we haven't broken any flops mark. Flops is short for
> > Floating point Operations. RC5 and DES are both integer-only calculations,
> > so there's no floating point involved at all. (Not that I doubt we'd kill
> > that terraflop number if there were, but our current numbers don't have
> > anything to do with it)
> > 
> 
> And I was saying, that is a calculated value.  It is calculated from 
> taking some refference processor (in X86 case it was P100), calculating 
> how many of those processors would be doing current load of X86es, and 
> than multiplying it with the number of known FLOPS of P100.  That was 
> done by D.Net staff (http://www.distributed.net/statistics/stats.html.
> I know that D.Net processing does NOT involve fp ops to be measured...

You can't scale the numbers at all meaningfully, though. I've got a couple
of Alpha CPUs involved, and their numbers, relatively speaking, suck. The
speed of a CPU for RC5 purposes is almost entirely based on the speed
that a particular CPU can shift data within a register. It has zilch to do
with floating-point performance.

> Can you at least check out the info before you start flaming people!!!!!!

Um, if you check, you'll see it's not a flame. You just made an incorrect
statement based on an incorrect assumption. I'm quite sure of my
information. 

The big thing you can extrapolate from the RC5 numbers is some aggregate
MegaShift/sec number, which is fairly meaningless.

					Dan

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