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Forum: GpuOwl 2022-05-12, 11:11
Replies: 2,772
Views: 379,984
Posted By preda
Ken, I don't understand what you propose there --...

Ken, I don't understand what you propose there -- to do the validation in parallel with the last bit of a preceding exponent, upon resume?
Forum: GpuOwl 2022-05-12, 11:01
Replies: 34
Views: 2,794
Posted By preda
If using gpuowl 7.x, also try with -use...

If using gpuowl 7.x, also try with
-use TRIG_COMPUTE=0
or 1, or 2 (2 being the default).
The idea being that 2 does more compute, 0 does more memory accesses, and 1 is intermediary between those...
Forum: Information & Answers 2022-05-10, 15:49
Replies: 8
Views: 808
Posted By preda
Never delete anything. Create a "temporary"...

Never delete anything. Create a "temporary" directory somewhere, and just *move* what you want to delete there.

Later on, you can always move it back if the mood changes.

When everything is...
Forum: GPU Computing 2022-04-10, 17:22
Replies: 374
Views: 97,570
Posted By preda
It was in December 2020. I imagine it must...

It was in December 2020.

I imagine it must have been painful to lose so many R7s, sorry for that. Indeed a pity they're not made anymore, in retrospective I should've bought a few more just for my...
Forum: GPU Computing 2022-04-10, 08:21
Replies: 374
Views: 97,570
Posted By preda
I had one R7 GPU die on me following something...

I had one R7 GPU die on me following something PSU related, not sure exactly what happened there. But the symptoms were similar, the lights/fans were ON but the GPU was not detected. I looked in the...
Forum: GpuOwl 2022-03-27, 06:16
Replies: 2,772
Views: 379,984
Posted By preda
But maybe something should be done to fix the...

But maybe something should be done to fix the root of the problem, which is IMO that the proof file was not saved, but the checkpoint was advanced.

Edit: I see now what the code does. If it can't...
Forum: GpuOwl 2022-03-27, 05:59
Replies: 2,772
Views: 379,984
Posted By preda
Laur, the version I'm using (v7.2-86) does keep...

Laur, the version I'm using (v7.2-86) does keep many checkpoints to restart from, and whatsmore the number is configurable (so it's possible to keep much more if desired), and they also have the...
Forum: GpuOwl 2021-11-19, 14:49
Replies: 5
Views: 843
Posted By preda
I don't understand what happened. The proof...

I don't understand what happened. The proof residues are written once only, afterwards they are only read. The check of residues at startup is done CPU-side only (it's a very simple checksum over the...
Forum: Software 2021-11-04, 09:26
Replies: 10
Views: 1,723
Posted By preda
P-1 only "eliminates" an exponent if a factor is...

P-1 only "eliminates" an exponent if a factor is found.

I suggest using bounds of at least B1=1M,B2=20M. (I use B1=3M and B2=60M myself).
Forum: Software 2021-09-24, 08:31
Replies: 7
Views: 1,442
Posted By preda
In my understanding, VIRT in "top" for a process...

In my understanding, VIRT in "top" for a process indicates "virtual" memory that is not mapped to physical memory. That would happen for example after a malloc() but before writing anything to the...
Forum: Lounge 2021-09-06, 19:12
Replies: 1,936
RIP
Views: 226,054
Posted By preda
Ivan Patzaichin

Ivan Patzaichin was a legendary Romanian canoeist: https://en.wikipedia.org/wiki/Ivan_Patzaichin
Forum: Math 2021-07-06, 17:27
Replies: 24
Views: 4,025
Posted By preda
Maybe related, please see the thread about what I...

Maybe related, please see the thread about what I coined "PRP-1": https://www.mersenneforum.org/showthread.php?t=23628
Forum: mersenne.ca 2021-06-14, 19:20
Replies: 16
Views: 2,438
Posted By preda
Yes AFAIK the new formula is correct. ...

Yes AFAIK the new formula is correct.

fancySum(a, b) = a + b * (1 - a) == a + b - a * b
Forum: mersenne.ca 2021-06-14, 06:03
Replies: 16
Views: 2,438
Posted By preda
Let's consider a story: on a dangerous trip,...

Let's consider a story: on a dangerous trip, somebody must first cross a lake, and afterwards the forest. In the lake there's an aligator that would eat him with 90% chances. In the unlikely event...
Forum: Software 2021-06-02, 13:58
Replies: 54
Views: 12,972
Posted By preda
There's one more interesting factoid about the...

There's one more interesting factoid about the difference between "classic" FFT and NTT:

when working with complex numbers in the classic FFT, the inverse transform is equal to the conjugate of...
Forum: Software 2021-06-02, 13:33
Replies: 54
Views: 12,972
Posted By preda
In the same setup (FFT 4M, Radeon VII, exponent...

In the same setup (FFT 4M, Radeon VII, exponent around 107M) I gained about 33% performance by tweaking (with inline assembly) the low-level modular primitives (add, sub, mul). So now the performance...
Forum: Software 2021-05-27, 07:03
Replies: 54
Views: 12,972
Posted By preda
I was testing on a Radeon VII.

I was testing on a Radeon VII.
Forum: Software 2021-05-26, 20:33
Replies: 54
Views: 12,972
Posted By preda
I did some preliminary performance measurements,...

I did some preliminary performance measurements, and the initial results are a bit dissapointing -- the NTT being about 3x slower than the equivalent FP64. It seems the code is compute-bound now (vs....
Forum: Software 2021-05-25, 06:50
Replies: 54
Views: 12,972
Posted By preda
Yes this is one option I considered. It's tricky...

Yes this is one option I considered. It's tricky to do the "shift every (couple of) FFT levels" well, because if it's done the conservative way (shift every level) it's wasteful on the precision...
Forum: Software 2021-05-25, 06:41
Replies: 54
Views: 12,972
Posted By preda
There is a difference of 3 bits between M61 and...

There is a difference of 3 bits between M61 and the above 64-bit prime, which explains 3/2=1.5 bits of the difference.

Another important element that enables 25bits is that now I'm using...
Forum: Software 2021-05-25, 00:49
Replies: 54
Views: 12,972
Posted By preda
Lately I've been experimenting with some non-FP64...

Lately I've been experimenting with some non-FP64 FFT transforms.

These are briefly some directions I've looked into, for representing the values that the FFT operates on:

1. a set of 4 SP...
Forum: Math 2021-05-17, 12:17
Replies: 2
Views: 1,165
Posted By preda
On the GPU, we are limited by the small number of...

On the GPU, we are limited by the small number of "VGPRs" (registers) per workgroup that are available. Because we're operating at the upper limit of VGPRs, there's no much room to operate on two...
Forum: GpuOwl 2021-05-13, 17:54
Replies: 4
Views: 1,066
Posted By preda
It's fine to run without a config.txt if you...

It's fine to run without a config.txt if you don't need it. It's just a facility to put the flags that you would otherwise pass on the command line, in a file. The format is exactly what you'd put on...
Forum: Hardware 2021-04-29, 10:05
Replies: 77
Views: 14,175
Posted By preda
TF (trial factoring) does not use FFTs. For...

TF (trial factoring) does not use FFTs.

For primality testing Mersenne numbers, there is LL and PRP; the two are very similar from an implementation perspective. They both require squaring very...
Forum: Software 2021-04-27, 11:20
Replies: 54
Views: 12,972
Posted By preda
The cost of small multiplication

(sorry for the below being so trivial)

At the core of a FFT there are "small multiplications", word-size or some small multiple of word-size, and I've been thinking a bit about their cost.
...
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