COMPLETE!!!! Thinking out loud about getting under 20M unfactored exponents

[axn]

Unlike previous versions which run into diminishing returns the more RAM you throw at it, 30.8 efficiency keeps on going up as you increase your RAM allocation. So any recommendation that doesn't take into account the available RAM is going to be sub-optimal (and not just by a little)

We don't need to cut it so close to the required probabilities. Pick reasonably large B1, let P95 choose the B2. We'll still complete the range _much_ faster than we would with previous versions. If it turns out that we're getting much larger probabilities than is needed, we can dial back B1 a bit.

[Prime95]

I had wanted to keep 30.8 out of the general public's eye, but someone created a 30.8 thread.
I've moved all the 30.8 posts there: https://www.mersenneforum.org/showthread.php?t=27366

We now return this thread to its regular programming....

[petrw1]

No crashes or weird results so far...

i5-2500 with 12GB RAM allocated; B1/B2 of 600K/90M:
28.0M exponent
Stage 1: 51 Min
Stage 2: 55 Min

i5-3570 with 14GB RAM; B1/B2 of 600K/90M:
24.7M exponent
Stage 1: 36 Min
Stage 2: 31 Min

i5-3570 with 6.5GB RAM; B1/B2 of 600K/75M:
24.7M exponent
Stage 1: 35 Min
Stage 2: 51 Min

i5-3570K with 3GB RAM; B1/B2 of 600K/75M:
24.7M exponent
Stage 1: 31 Min
Stage 2: 85 Min

i5-3570 with 14GB RAM; B1/B2 of 600K/90M:
6.1M exponent
Stage 1: 7 Min
Stage 2: 3 Min

i5-3570K with 3GB RAM; B1/B2 of 600K/75M:
6.1M exponent
Stage 1: 6 Min
Stage 2: 5 Min

My take: in the 2x.xM ranges
12+ GB seems decent
6.5GB so-so
3GB not enough ... better suited for the lower exponents (i.e 6M)

P.S. 2 cases now trying to stop Prime95 early in Stage 2;
right after Stage 2 Init complete.
And it takes a very long time ... more than 5 minutes and still waiting.
...it stopped only after Stage 2 completed.

[axn]

Originally Posted by petrw1

My take: in the 2x.xM ranges
12+ GB seems decent

Do you have machines with more RAM? Like 32 GB or more? You'll be surprised (or not) at how much more speedup could be gained by using more RAM. For 2x.x, I would think something like 100+ GB will be "optimal".

[alpertron]

Originally Posted by petrw1

No crashes or weird results so far...
...

i5-3570 with 14GB RAM; B1/B2 of 600K/90M:
6.1M exponent
Stage 1: 7 Min
Stage 2: 3 Min

i5-3570K with 3GB RAM; B1/B2 of 600K/75M:
6.1M exponent
Stage 1: 6 Min
Stage 2: 5 Min

I'm running a more intensive test. The contents of the file worktodo.txt is:

[Worker #1]
Pminus1=1,2,9325159,-1,50000000,50000000000,"8056937377,16207126343,95788033249,799651034569,2894827758689,1416068886691577,36098431074477463,635315498297290933609,6214794856879965540791"

It took 26 hours for step 1 in an I5 3470. and now it is running step 2 for 35 hours with 8 GB used for Prime95. According to the values above, probably Prime95 will require 10 days to complete step 2.

[axn]

Originally Posted by alpertron

It took 26 hours for step 1 in an I5 3470. and now it is running step 2 for 35 hours with 8 GB used for Prime95. According to the values above, probably Prime95 will require 10 days to complete step 2.

You should have given it a _lot_ more RAM.

[alpertron]

My system has 16 GB of RAM, and I have several programs running at the same time. That's why I give 8 GB to Prime95. Otherwise the system would run slower.

[Xyzzy]

We have 256GB of memory.

If you want a test/benchmark done just post the worktodo entry that we need to use.

[petrw1]

Originally Posted by axn

Do you have machines with more RAM? Like 32 GB or more? You'll be surprised (or not) at how much more speedup could be gained by using more RAM. For 2x.x, I would think something like 100+ GB will be "optimal".

Yes I have a 32GB machine that with 30.7 did P1 4x faster than these machines.
It's at the doctor. I'll have it later today.

[axn]

Originally Posted by petrw1

Yes I have a 32GB machine that with 30.7 did P1 4x faster than these machines.
It's at the doctor. I'll have it later today.

Originally Posted by alpertron

My system has 16 GB of RAM, and I have several programs running at the same time. That's why I give 8 GB to Prime95. Otherwise the system would run slower.

Yes, with only 16GB available RAM, I understand that you can't give more. Unfortunately, you could've saved several days of computation if you had more RAM.

[petrw1]

Originally Posted by petrw1

i5-3570K with 3GB RAM; B1/B2 of 600K/75M:
24.7M exponent
Stage 1: 31 Min
Stage 2: 85 Min

3GB not enough ... better suited for the lower exponents (i.e 6M)

I squeezed this PC from 3GB to 5GB and the Stage 2 time dropped from 85 minutes to 50 minutes.