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Message boards : Proth Prime Search : Smaller FFT size, longer CPU time

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Profile BurProject donor
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Joined: 25 Feb 20
Posts: 514
ID: 1241833
Credit: 412,173,326
RAC: 19,150
321 LLR Ruby: Earned 2,000,000 credits (2,092,823)Cullen LLR Ruby: Earned 2,000,000 credits (2,315,295)ESP LLR Ruby: Earned 2,000,000 credits (2,151,088)Generalized Cullen/Woodall LLR Ruby: Earned 2,000,000 credits (2,620,968)PPS LLR Jade: Earned 10,000,000 credits (15,300,560)PSP LLR Ruby: Earned 2,000,000 credits (2,064,832)SoB LLR Ruby: Earned 2,000,000 credits (2,434,466)SR5 LLR Ruby: Earned 2,000,000 credits (2,065,004)SGS LLR Ruby: Earned 2,000,000 credits (2,027,649)TRP LLR Ruby: Earned 2,000,000 credits (2,089,856)Woodall LLR Ruby: Earned 2,000,000 credits (2,112,258)321 Sieve (suspended) Ruby: Earned 2,000,000 credits (2,107,153)PPS Sieve Turquoise: Earned 5,000,000 credits (5,096,952)AP 26/27 Turquoise: Earned 5,000,000 credits (5,797,662)GFN Jade: Earned 10,000,000 credits (10,874,159)WW Double Silver: Earned 200,000,000 credits (349,980,000)PSA Amethyst: Earned 1,000,000 credits (1,042,601)
Message 145337 - Posted: 18 Nov 2020 | 18:28:53 UTC
Last modified: 18 Nov 2020 | 18:30:51 UTC

While browsing PPS Mega tasks, I saw that some took 4100 s, some 5400 s. I assumed the latter had the larger FFT size and larger k, but not so.

The 4100 s tasks had FFT = 256k, the 5400 s ones had FFT = 240k.

Here are examples of each: 4100 s and 5400 s or the whole list here.

The difference seems to be the pass1 and pass2, in one case pass1 is larger, in the other pass2 is larger. And a is either 3 or 5.

What do these parameters mean and how do they influence the CPU time in such a way that smaller FFT size means longer CPU time? Especially since the tasks with shorter run times had the larger k and accordingly larger FFT.
____________
1281979 * 2^485014 + 1 is prime ... no further hits up to: n = 5,700,000

Profile Eudy SilvaProject donor
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Joined: 26 Aug 17
Posts: 2033
ID: 918937
Credit: 572,885,967
RAC: 209,831
Discovered 3 mega primesFound 2 primes in the 2018 Tour de PrimesFound 1 prime in the 2019 Tour de PrimesFound 1 prime in the 2020 Tour de PrimesFound 1 prime in the 2021 Tour de Primes321 LLR Amethyst: Earned 1,000,000 credits (1,187,213)Cullen LLR Amethyst: Earned 1,000,000 credits (1,349,947)ESP LLR Amethyst: Earned 1,000,000 credits (1,151,976)Generalized Cullen/Woodall LLR Amethyst: Earned 1,000,000 credits (1,199,207)PPS LLR Sapphire: Earned 20,000,000 credits (30,057,152)PSP LLR Amethyst: Earned 1,000,000 credits (1,476,639)SoB LLR Ruby: Earned 2,000,000 credits (2,432,091)SR5 LLR Ruby: Earned 2,000,000 credits (4,140,473)SGS LLR Amethyst: Earned 1,000,000 credits (1,462,951)TRP LLR Ruby: Earned 2,000,000 credits (2,010,675)Woodall LLR Amethyst: Earned 1,000,000 credits (1,231,973)321 Sieve (suspended) Amethyst: Earned 1,000,000 credits (1,119,749)Generalized Cullen/Woodall Sieve (suspended) Amethyst: Earned 1,000,000 credits (1,005,331)PPS Sieve Double Bronze: Earned 100,000,000 credits (100,101,845)AP 26/27 Double Bronze: Earned 100,000,000 credits (100,120,852)GFN Double Bronze: Earned 100,000,000 credits (120,595,074)WW Double Silver: Earned 200,000,000 credits (200,192,000)PSA Ruby: Earned 2,000,000 credits (2,059,222)
Message 145348 - Posted: 18 Nov 2020 | 20:25:28 UTC - in response to Message 145337.

There was some talking about this last year:
https://www.primegrid.com/forum_thread.php?id=8628&nowrap=true
____________

"Accidit in puncto, quod non contingit in anno."
Something that does not occur in a year may, perchance, happen in a moment.

Profile BurProject donor
Volunteer tester
Avatar
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Joined: 25 Feb 20
Posts: 514
ID: 1241833
Credit: 412,173,326
RAC: 19,150
321 LLR Ruby: Earned 2,000,000 credits (2,092,823)Cullen LLR Ruby: Earned 2,000,000 credits (2,315,295)ESP LLR Ruby: Earned 2,000,000 credits (2,151,088)Generalized Cullen/Woodall LLR Ruby: Earned 2,000,000 credits (2,620,968)PPS LLR Jade: Earned 10,000,000 credits (15,300,560)PSP LLR Ruby: Earned 2,000,000 credits (2,064,832)SoB LLR Ruby: Earned 2,000,000 credits (2,434,466)SR5 LLR Ruby: Earned 2,000,000 credits (2,065,004)SGS LLR Ruby: Earned 2,000,000 credits (2,027,649)TRP LLR Ruby: Earned 2,000,000 credits (2,089,856)Woodall LLR Ruby: Earned 2,000,000 credits (2,112,258)321 Sieve (suspended) Ruby: Earned 2,000,000 credits (2,107,153)PPS Sieve Turquoise: Earned 5,000,000 credits (5,096,952)AP 26/27 Turquoise: Earned 5,000,000 credits (5,797,662)GFN Jade: Earned 10,000,000 credits (10,874,159)WW Double Silver: Earned 200,000,000 credits (349,980,000)PSA Amethyst: Earned 1,000,000 credits (1,042,601)
Message 145388 - Posted: 19 Nov 2020 | 17:34:11 UTC - in response to Message 145348.

Ok, thanks I will continue in that thread.
____________
1281979 * 2^485014 + 1 is prime ... no further hits up to: n = 5,700,000

Message boards : Proth Prime Search : Smaller FFT size, longer CPU time

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