On Thursday 06 March 2003 13:03, Daran wrote: > > Based upon what I know of the algorithms involved, it *ought* to be the > case that you should do any P-1 work on the machine which can give it the > most memory, irrespective of processor type.
... assuming the OS allows a single process to grab the amount of memory configured in mprime/Prime95 (this may not always be the case, at any rate under linux, even if adequate physical memory is installed.) > > However, some time ago, I was given some information on the actual P-1 > bounds chosen for exponents of various sizes, running on systems of various > processor/memory configurations. It turns out that P4s choose *much > deeper* P-1 bounds than do other processors. For example: > > 8233409,63,0,Robreid,done,,40000,450000,,Athlon,1.0/1.3,90 > 8234243,63,0,Robreid,done,,40000,450000,,Celeron,540,80 > 8234257,63,0,Robreid,done,,45000,742500,,P4,1.4,100 > > The last figure is the amount of available memory. The differences between > 80MB and 100MB, and between 8233409 and 8234257 are too small to account > for the near doubling in the B2 bound in the case of a P4. Yes, that does seem odd. I take it the software version is the same? The only thing that I can think of is that the stage 2 storage space for temporaries is critical for exponents around this size such that having 90 MBytes instead of 100 MBytes results in a reduced number of temporaries, therefore a slower stage 2 "iteration time", therefore a significantly lower B2 limit. I note also that the limits being used are typical of DC assignments. For exponents a bit smaller than this, using a P3 with memory configured at 320 MBytes (also no OS restriction & plenty of physical memory to support it) but requesting "first test" limits (Pfactor=<exponent>,<tfbits>,0) I'm getting B2 ~ 20 B1 e.g. [Thu Mar 06 12:07:46 2003] UID: beejaybee/Simon1, M7479491 completed P-1, B1=90000, B2=1732500, E=4, WY1: C198EE63 The balance between stage 1 and stage 2 should not really depend on the limits chosen since the number of temporaries required is going to be independent of the limit, at any rate above an unrealistically small value. Why am I bothering about this exponent? Well, both LL & DC are attributed to the same user... not really a problem, but somehow it feels better to either find a factor or have an independent triple-check when this happens! Regards Brian Beesley _________________________________________________________________________ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
