Whither TF?

[Rodrigo]

Taking a quick break from the rigors of the publishing industry. I have an observation, and a question based on it.

One of my computers is assigned to do TF. When it started crunching some 15 months ago, it was getting exponents in the low 100M range. Now, some 15 months later, it's receiving exponents north of 320M. Obviously, the advent of GPU computing has had an effect. At this rate (which no doubt will continue to increase), trial factoring will hit OBD territory sometime in 2015.

When that happens, how will the TF portion of GIMPS proceed -- will it move into billion-digit exponents; recap previous exponents at deeper bit levels; or something else?

Just curious.

Rodrigo

[davieddy]

Originally Posted by Rodrigo

Taking a quick break from the rigors of the publishing industry. I have an observation, and a question based on it.

One of my computers is assigned to do TF. When it started crunching some 15 months ago, it was getting exponents in the low 100M range. Now, some 15 months later, it's receiving exponents north of 320M. Obviously, the advent of GPU computing has had an effect. At this rate (which no doubt will continue to increase), trial factoring will hit OBD territory sometime in 2015.

When that happens, how will the TF portion of GIMPS proceed -- will it move into billion-digit exponents; recap previous exponents at deeper bit levels; or something else?

Just curious.

Rodrigo

TF on GPUs is so shit hot, that CPUs better
find something else to do.

And since it takes as long to TF from X to X+1 bits as it does from 0 to X, all work above 60M is of neglible value as far as GIMPS is concerned.

David

[axn]

Originally Posted by Rodrigo

One of my computers is assigned to do TF. When it started crunching some 15 months ago, it was getting exponents in the low 100M range. Now, some 15 months later, it's receiving exponents north of 320M. Obviously, the advent of GPU computing has had an effect.

Not at all. This is strictly the CPUs (TF to low limits) that is causing that wavefront to advance. GPUs have had practically zero influence on this. And it'll stay that way -- GPU TF is not yet automated. Only a handful of enthusiasts on this board are actually using it.

Originally Posted by Rodrigo

At this rate (which no doubt will continue to increase), trial factoring will hit OBD territory sometime in 2015.

GIMPS currently has a hard stop at 1,000,000,000. I don't think George is in any rush to extend that.

Originally Posted by Rodrigo

When that happens, how will the TF portion of GIMPS proceed -- will it move into billion-digit exponents; recap previous exponents at deeper bit levels; or something else?

[NBtarheel_33]

Originally Posted by Rodrigo

recap previous exponents at deeper bit levels

You might remember this is what happened after we ran out of 63->64 bit assignments in August 2010. Once we finish TFing everything to 65, the LMH assignments will likely start over again at 100M, this time TFing to 66. Note that this will take twice as long as the effort from 64 to 65. So if it takes, say, 18 months (August 2010 - February 2012) to finish everything to 65 bits, we will be busy for three years (!) with finishing everything to 66 bits. When you also consider that the nine-figure exponents all need to be TFed to at least 72, we will certainly be busy for the foreseeable future, even with the lumberjacks and the GPUs.

[ATH]

It's better to keep TF exponents below 1 billion to higher bit ranges instead of moving beyond 1 billion, since LL wavefront probably won't get there in our lifetimes unless some major advances in algorithm or quantum computing.

[NBtarheel_33]

Originally Posted by ATH

since LL wavefront probably won't get there in our lifetimes

Once I jump the broom into the Great Beyond(TM), I plan on picking up right where I left off. First thing is to talk the angel processing new arrivals into letting me install Prime95 on her quantum computer.

(And she'll say, "But, sir, I already have it testing MMMM127!". Or, everyone will start laughing, as I get handed a paper containing a 2-line proof that there are no Mersenne primes above 2^60,000,000-1.)

[Rodrigo]

Originally Posted by NBtarheel_33

Once I jump the broom into the Great Beyond(TM), I plan on picking up right where I left off. First thing is to talk the angel processing new arrivals into letting me install Prime95 on her quantum computer.

(And she'll say, "But, sir, I already have it testing MMMM127!". Or, everyone will start laughing, as I get handed a paper containing a 2-line proof that there are no Mersenne primes above 2^60,000,000-1.)

So higher bit levels it is. Thanks, guys!

Rodrigo

[Rodrigo]

Originally Posted by axn

Not at all. This is strictly the CPUs (TF to low limits) that is causing that wavefront to advance. GPUs have had practically zero influence on this.

axn,

The month-to-month jump in the size of the TF exponents my computer is completing (recently assigned), has grown from 12.4M (10/8/10 - 11/8/10) to 24.2M (10/8/11 - 11/8/11).

This was not a fluke: the jump in the period 9/8/10 - 10/8/10 was 9.7M, while the jump in the period 9/8/11 - 10/8/11 was 20.7M. Here are the monthly jumps (every month on day 8):

Date - Exponent - Difference
11/10 1259xxxxx
12/10 1383xxxxx +124xxxxx
01/11 1478xxxxx +095xxxxx
02/11 1614xxxxx +136xxxxx
03/11 1737xxxxx +123xxxxx
04/11 1862xxxxx +125xxxxx
05/11 2022xxxxx +160xxxxx
06/11 2193xxxxx +171xxxxx
07/11 2369xxxxx +176xxxxx
08/11 2549xxxxx +180xxxxx
09/11 2739xxxxx +180xxxxx
10/11 2944xxxxx +205xxxxx
11/11 3186xxxxx +242xxxxx

So the month-to-month jumps were rather flat from 11/10 to 4/11, and since then they've been rising at an increasing pace.

Help me to understand. Are there that many more CPUs doing TF this fall, than there were last fall? What happened in April/May of this year, to account for the sudden (and growing) jump in the rate of increase? Are certain ranges being skipped?

Please note -- I'm not being contentious, just trying to get a handle on how this works.

Thanks!

Rodrigo

[chalsall]

Originally Posted by Rodrigo

The month-to-month jump in the size of the TF exponents my computer is completing (recently assigned), has grown from 12.4M (10/8/10 - 11/8/10) to 24.2M (10/8/11 - 11/8/11).

You are off by an order of (base 10) magnitude. To your above, it's 124M to 242M.

Originally Posted by Rodrigo

So the month-to-month jumps were rather flat from 11/10 to 4/11, and since then they've been rising at an increasing pace.

Remember that TF, unlike LL, gets faster the higher you go.

Originally Posted by Rodrigo

Please note -- I'm not being contentious, just trying to get a handle on how this works.

And please note we try to be as gentle as we can, but will still point out when you (or anyone) makes an error.

It's in our nature....

[bcp19]

Originally Posted by chalsall

You are off by an order of (base 10) magnitude. To your above, it's 124M to 242M.

He had it right, the exponent 'jumped' by 12.4 mil and the jumps increased to 24.2 million. He was talking about jumps, not the actual exponent.

[chalsall]

Originally Posted by bcp19

He had it right, the exponent 'jumped' by 12.4 mil and the jumps increased to 24.2 million. He was talking about jumps, not the actual exponent.

Thanks for the correction. You (and Rodrigo) are correct -- I misread it.