P-1 coordination thread - discussion

[engracio]

e,

If you are talking about in general. No we will not find that many factors using P-1 but this was always the case. Overall we will also find less factors since the sieve is always progressing. Before we had a good shot at finding factors above 900T. Now that we have sieved out to around 1300T and bionic has sieved a good portion between 1500T and 2000T our chances of finding factors less than 2000T or 2P are almost zero since sieve finds all factors including those found by P-1 factoring.

Now inregards to your settings and the current settings.

You were using
B1=80K and B2=920K this is a B1 to B2 ratio of 11.5.

Currently we are suggesting using a
B1= 130K and B2=2200K this is a B1 to B2 ratio of 16.9

The suggested setting will find more factors that your old setting, but it may find less factors per unit of time. (Not sure we will see, also if we start to fall behind in P-1 we will proably reduce those B1 B2 values).

(BTW the stage that uses the most memory is stage 2, memory requirements are based upon the size of the B2 value.

The higher the B1 and B2 the more chance we have of finding a factor but the longer each test will take. There are some efficency issues here with values of n, the sieve level, B1, B2, and of course if we are testing each k/n pair prior to prime testing.

The biggest issue here is that we do at leasat some minimal testing of each k/n pair with P-1 prior to primality testing.

Now I think in your case we had talked and I suggested that you use a smaller B1:B2 ratio since you were memory limited.

If this is your case simply start to decrease the B2 value to a minimum of B1:B2 of 12, or B1=130k B2=1600k until you do not have any memory issues.

I hope this helps and I know alot of what I said above you already know.

Joe, vjs

Thanks for the info. Yes most of the info you stated above I already or have known about it. Just kind of rusty. My biggest thing is last year I was completing 1 wu per 3 to 4 hours per cpu and finding a factor every 6 to 8 wu. Now it seems like everything doubled but with very little result if any. So far out of 6 cpu/cores it found no factor yet. Is the cost/benefit ratio worth it? We all knew P1 will eventually run into this wall sooner or later. Is sooner now? I will complete my reserved range and see if we did hit the wall. My next reservation will tell me how I feel about it. Thanks.

e

[vjs]

e,

As far as cost benift you were finding really alot of factors last year. Alot more than I expected. The cost benifit really comes in when you look at how many factors you find per unit time and in that unit of time how many tests could have you done.

The ratio although some could argue should be 2 factors for every 3 tests... Yup really!!!

For the simple fact that we will probably test each k/n pair twice.

Where we were before is probably around a 1:1 ratio if not more. This ratio was totally sub-par, since we could factor tests out quicker than we could test them. I'd say stick with the P-1 for no and look at the time requirements. Besides we could always use those CPU' sin the testing fold if that's where they are best suited.