[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

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


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