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-   -   CUDALucas not redoing iterations with larger FFT (https://www.mersenneforum.org/showthread.php?t=19690)

patrik 2014-09-11 14:52

CUDALucas not redoing iterations with larger FFT
 
I just had the following problem with CUDALucas v2.04 Beta:

[CODE]Iteration 24020000 M( 36163033 )C, 0x47f4b44347a56afb, n = 1920K, CUDALucas v2.04 Beta err = 0.2812 (1:07 real, 6.7233 ms/iter, ETA 22:40:21)
Iteration 24030000 M( 36163033 )C, 0x5f9ad444634e1734, n = 1920K, CUDALucas v2.04 Beta err = 0.2734 (1:08 real, 6.7129 ms/iter, ETA 22:37:07)
Iteration = 24037901 >= 1000 && err = 0.35938 >= 0.35, fft length = 1920K, not writing checkpoint file (because -t is disabled) and exiting.[/CODE]

In this case Prime95 would increase the FFT length and restart from the last checkpoint with a larger FFT size, but CUDALucas just fails at the same point after every restart.

Is there a way I can manually set it to use a larger FFT to get past this point?

(I know this is not the lastest version of CUDALucas, but if I run a later version I use on another computer I just get:
./CUDALucas-2.05-Beta-r64-Linux-x86-64: error while loading shared libraries: libcufft.so.5.5: cannot open shared object file: No such file or directory )

patrik 2014-09-11 20:00

I managed to get past the point using the same fft size by changing 0.35 in the source to 0.40, and recompiling the program. (I compiled it from source when I first started using this version.)

I used the new version only for 12651 iterations, then stopped it and switched back to the original version.

In a day or so I will se if this double-check matches the original test.

owftheevil 2014-09-12 00:56

If I remember correctly 2.04 can take a command line parameter eg, -f=4000k to use a particular size fft. On the other hand, I don't see any reason that what you have done will give an incorrect result.


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