The P-1 factoring CUDA program

[Aramis Wyler]

Originally Posted by James Heinrich

That is a bit disturbing.

M9090017 has factor 516770062491225473521, with a k of 28425142796280
k-factored = 2³ × 3 × 5 × 61 × 97 × 389 × 102913
minimal bounds to find this factor in stage2 would be B1=389,B2=102913
minimal bounds to find this factor in stage1 would be B1=102913

You ran this with B1=115000 so it should have found the factor, at least according to my understand of P-1

If I follow that correctly, then with a B1 of 110000 not only should it have found it in stage 1, but it should not have been possible to find in stage 2 (B1 too high). Is that right? Or could it have found it in stage 2 as a multiple of 102913 (like 205826)? further, if it did find it as a multiple of 102913, would it have given the same factor (516770062491225473521) as prime95 did in stage1?

[owftheevil]

You are all right. There's something weird going on here.

Edit: 102913 is pairing up with 1341143, which gets caught in stage 2. But I still don't know why stage 1 is not finding the factor.

Edit2. Found it. Stage 1 doesn't stand a chance of finding any factor at the moment. Its not looking at the right data. Fix coming this evening.

[Stef42]

I did some other exponents which had factors in low P-1 bounds.
Each and everyone of them was reported by prime95 in stage 1, CUDAPm1 found them in stage 2.

[James Heinrich]

Originally Posted by Stef42

Right after stage 1 finished and stage 2 was initiated, I got a popup saying that CUDAPm1 crashed.

Just for clarity, I have attached a screenshot showing this happening.

[James Heinrich]

Originally Posted by Stef42

I did some other exponents which had factors in low P-1 bounds.
Each and everyone of them was reported by prime95 in stage 1, CUDAPm1 found them in stage 2.

I tried looking for factor where k=1, so I tried

CUDAPm1 4444091 -b1 100 -b2 1000

Should've been found in stage1, actually it should have found 2 factors in stage 1:
8888183 k = 1
319974553 k = 36

But no factor(s) found:

Stage 1 complete, estimated total time = 0:00
Starting stage 1 gcd.
M4444091 Stage 1 found no factor (P-1, B1=100, B2=390390, e=6, n=256K CUDAPm1 v0.00)
Starting stage 2.
Zeros: 12986, Ones: 24934, Pairs: 8522

One side note:

B2 should be at least 390390, increasing it.
Starting stage 1 P-1, M4444091, B1 = 100, B2 = 390390, e = 6, fft length = 256K

Is the B2>=390390 a fixed limitation, or tied to the exponent, or FFT, or...? It could be interesting to play with CUDAPm1 with a smaller B2 bound than that, if possible.

[chalsall]

Originally Posted by owftheevil

You are all right. There's something weird going on here.

Edit: 102913 is pairing up with 1341143, which gets caught in stage 2. But I still don't know why stage 1 is not finding the factor.

Edit2. Found it. Stage 1 doesn't stand a chance of finding any factor at the moment. Its not looking at the right data. Fix coming this evening.

A fundamental truth: software is hard. Computers do exactly what we tell them to do (usually; damn bad hardware!). My second born for a DWIM command!

This is why extensive testing -- by many different people -- is required.

Good work everyone!

[James Heinrich]

Originally Posted by James Heinrich

actually it should have found 2 factors in stage 1

On the plus side, it did find all 3 known factors in stage2, albeit as the composite of all of them:

M4444091 has a factor: 1809798096458971047321927127 (P-1, B1=100, B2=390390, e=6, n=256K CUDAPm1 v0.00)

[Stef42]

Originally Posted by James Heinrich

One side note:Is the B2>=390390 a fixed limitation, or tied to the exponent, or FFT, or...? It could be interesting to play with CUDAPm1 with a smaller B2 bound than that, if possible.

B2 should be at least 1560000, increasing it.
Starting stage 1 P-1, M9090017, B1 = 120000, B2 = 1560000, e = 6, fft length = 5
12K

I'm not that good in figuring out what it's bound too. Example might help tough.

[James Heinrich]

Playing with some limits checking.

smallest exponent: M86243 (aka 28^th Mersenne Prime) -- checked for and warns user

non-prime exponents: checks for and warns user

maximum exponent: uncertain. Haven't tested extensively, but testing in OBD range isn't working nicely: "CUDAPm1 3333333011 -b1 100 -b2 1000" crashes quickly ("CUDAPm1 has stopped working...", whereas "CUDAPm1 3333333011" (no bounds specified) just sits there (no GPU load, no crash, no progress). Just under 2³¹ (M2000000011) does the same thing.
Just under 2³⁰, it doesn't crash, but the error message is somewhat cryptic to me as an end-user:

CUDAPm1 1000000009 -b1 1000 -b2 10000
over specifications Grid = 110592
try increasing threads (512) or decreasing FFT length (55296K)

Specifying a negative exponent (e.g. "CUDAPm1 -3333333011") doesn't work, but doesn't issue any warnings either. I guess it's being treated as an unrecognized parameter, but a warning should be generated for unrecognized parameters.

[owftheevil]

Threads is a parameter you can set in the ini file. 1024 is the largest possible value. That value should enable 1000000009 to run.

[c10ck3r]

Q? about proto-p-1-cuda...
Is the does it write a .bu or .bu2 file like P95 does? If so, are they compatible? i.e. could I run Stage 1 on GPU and Stage 2 on CPU?