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Old 2022-12-06, 15:03   #2685
Madpoo
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Quote:
Originally Posted by Andrew Usher View Post
It's hard to believe no one has noticed, but for the past 2 weeks the contributions of TJAOI's main factor search have been categorised incorrectly. The smallest exponents are being recorded as ECM and P-1 rather than TF; as he actually does ECM (but not P-1) this is especially problematic.

It seems to be PrimeNet's fault, so I am posting it here, but I claim no knowledge of why it is occurring, but it should not be. Any fix needs to be retroactive to Nov. 24 (the first day the problem occurred), so the sooner it is addressed the better.
Could you provide an example exponent I can look at? Thanks.
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Old 2022-12-07, 00:03   #2686
Andrew Usher
 
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If you need one to examine the non-public information, try M9891151 which has a bogus 'ECM' factor followed by a real ECM factor a week later. The problem is also easily seen when seeing the list of TJAOI submissions on 'recent results', or on mersenne.ca where I found it.
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Old 2022-12-07, 16:37   #2687
Madpoo
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Quote:
Originally Posted by Andrew Usher View Post
If you need one to examine the non-public information, try M9891151 which has a bogus 'ECM' factor followed by a real ECM factor a week later. The problem is also easily seen when seeing the list of TJAOI submissions on 'recent results', or on mersenne.ca where I found it.
Ah, I see. I'll defer to George for the confirmation on this, but my understanding is that, in the absence of any other info to the contrary, if a factor is found for smaller exponents (I don't remember what the threshold is), the assumption is that it was found via ECM and not TF.

TJAOI uses some custom code to find factors and are not typically assigned, so there's no information on what actual method was used to find it (ECM, TF, etc). The raw result line that was submitted is literally just this:
M9891151 has a factor: 222093838040213055689

I don't know if this answers your question or not, but I think that's all that's happening. We have no way of knowing independently how these factors were found so it's just a basic categorization based on exponent size.

Again, I'll defer to George (or James might know also) on if I'm right about that.

^^^ I just dug into the code and I'm pretty sure I followed the threads correctly and the threshold for "unknown" factors like that will assume ECM up to 16M if the # of bits in the factor is > 55. If the # of bits is <=55 then it assumes TF although honestly, I wouldn't expect we'd find any more of those.

I mean, it'd be nice if TJAOI's code would include the basic details that other clients do, like if it's doing TF, include the bits from/to, and if it's ECM include the bounds, etc. but a factor is a factor.

EDIT: While I'm at it, I'll point out that if the factor is for an exponent above 16M, there's a lookup table that sets the cutoff level between P-1 and TF based on the exponent size and the current work on where TF bit levels are at. The code will lookup the exponent, find the current set point for TF work and if the factor is below that bit length, it assumes TF, and if above, it assumes P-1 with B1=800000.

Again, this is just a basic assumption when the client didn't provide any information on how the factor was found. Primenet will guess and dump it into TF, ECM, or P-1 as a best guess.

Last fiddled with by Madpoo on 2022-12-07 at 16:50
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