Force FFT-size to be used

kruoli · 2017-11-16, 21:39

Hey,

I'm trying to execute non-PrimeNet-work like this (just as example):

Code:

PRP=N/A,1,2,1000000,51,99,0,3,1
PRP=N/A,1,2,1000000,35181,99,0,3,1

The first line will be executed with 64 K FFT, the second line with 100 K FFT. The bit sizes of the numbers are identical. The result is an extremely small round-off. Am I mistaken when I think that both of them should be able to use the same FFT? If so, how can one enforce a specific FFT size for an assignment or even the whole worktodo-file, if all the numbers have similar size?

Batalov · 2017-11-16, 23:20

You can enforce FFT size.
But you shouldn't - in this case.
Bitsize is not the only factor for the FFT size choice. The k and/or c value will affect the FFT size too. (In this case c value is large, 35181.)

kruoli · 2017-11-17, 15:31

The round-off is really small. Even then you should not decrease FFT-size?

Just out of curiosity: How do you set a specific FFT?

ATH · 2017-11-17, 16:31

PRP=FFT2=64K,1,2,1000000,51,99,0,3,5

You should use type 5 PRP (the last 5 in the line) unless you are double checking a previous PRP result run with another type.

Edit: Nevermind I missed that it was not primenet work.

kruoli · 2017-11-17, 18:14

Quote:

Originally Posted by ATH

PRP=FFT2=64K,1,2,1000000,51,99,0,3,5

Nice, thanks! :)

2017-11-16, 21:39	#1
kruoli "Oliver" Sep 2017 Porta Westfalica, DE 2³·67 Posts	Force FFT-size to be used Hey, I'm trying to execute non-PrimeNet-work like this (just as example): Code: PRP=N/A,1,2,1000000,51,99,0,3,1 PRP=N/A,1,2,1000000,35181,99,0,3,1 The first line will be executed with 64 K FFT, the second line with 100 K FFT. The bit sizes of the numbers are identical. The result is an extremely small round-off. Am I mistaken when I think that both of them should be able to use the same FFT? If so, how can one enforce a specific FFT size for an assignment or even the whole worktodo-file, if all the numbers have similar size?

2017-11-17, 16:31	#4
ATH Einyen Dec 2003 Denmark 2·1,579 Posts	PRP=FFT2=64K,1,2,1000000,51,99,0,3,5 You should use type 5 PRP (the last 5 in the line) unless you are double checking a previous PRP result run with another type. Edit: Nevermind I missed that it was not primenet work. Last fiddled with by ATH on 2017-11-17 at 16:32

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2017-11-16, 23:20	#2
Batalov "Serge" Mar 2008 Phi(4,2^7658614+1)/2 2·47·101 Posts	You can enforce FFT size. But you shouldn't - in this case. Bitsize is not the only factor for the FFT size choice. The k and/or c value will affect the FFT size too. (In this case c value is large, 35181.)

2017-11-17, 15:31	#3
kruoli "Oliver" Sep 2017 Porta Westfalica, DE 1030₈ Posts	The round-off is really small. Even then you should not decrease FFT-size? Just out of curiosity: How do you set a specific FFT?