LL tests more credit-efficient than P-1?

ixfd64 · 2011-02-17, 19:56

I've assigned three desktops (all with i5-650 processors) to do P-1 factoring exclusively. From what I've noticed, each P-1 assignments takes about 1.8 days to complete gives exactly 4.6787 GHz-days of credit, provided that no factor is found in stage 1.

4.6787 / 1.8 = 2.6 GHz-days / (core * day)

However, another i5-650 desktop is LL-testing a 52M exponent. Each iteration takes 0.058 seconds; at this rate, it would take about 35 days for the assignment to finish.

An exponent of this size gives about 110.5 GHz-days of credit, or about 3.15 GHz-days / (core * day).

Is there an explanation for this discrepancy? Are LL tests more computationally intensive? Or does the code for calculating P-1 credit need to be adjusted?

Uncwilly · 2011-02-18, 01:30

You may want to see this thread:
http://www.mersenneforum.org/showthread.php?t=11411

nucleon · 2011-02-20, 12:24

How much memory did you allocate to P-1? I find allocating 500MB+ gave quicker results, than say 200MB.

Sorry I don't have exact figures. But I have 4x cores doing P-1 stage at the time, the 500MB core was sitting at 40% compelte, while the other was sitting at 25% ish. Note this figures are from memory. It's more qualative comparison than quantitive.

-- Craig

ixfd64 · 2011-02-20, 16:24

I'm using 384 MB per core.

2011-02-17, 19:56	#1
ixfd64 Bemusing Prompter "Danny" Dec 2002 California 2,341 Posts	LL tests more credit-efficient than P-1? I've assigned three desktops (all with i5-650 processors) to do P-1 factoring exclusively. From what I've noticed, each P-1 assignments takes about 1.8 days to complete gives exactly 4.6787 GHz-days of credit, provided that no factor is found in stage 1. 4.6787 / 1.8 = 2.6 GHz-days / (core * day) However, another i5-650 desktop is LL-testing a 52M exponent. Each iteration takes 0.058 seconds; at this rate, it would take about 35 days for the assignment to finish. An exponent of this size gives about 110.5 GHz-days of credit, or about 3.15 GHz-days / (core * day). Is there an explanation for this discrepancy? Are LL tests more computationally intensive? Or does the code for calculating P-1 credit need to be adjusted?

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2011-02-18, 01:30	#2
Uncwilly 6809 > 6502 """"""""""""""""""" Aug 2003 101×103 Posts 23D8₁₆ Posts	You may want to see this thread: http://www.mersenneforum.org/showthread.php?t=11411

2011-02-20, 12:24	#3
nucleon Mar 2003 Melbourne 1003₈ Posts	How much memory did you allocate to P-1? I find allocating 500MB+ gave quicker results, than say 200MB. Sorry I don't have exact figures. But I have 4x cores doing P-1 stage at the time, the 500MB core was sitting at 40% compelte, while the other was sitting at 25% ish. Note this figures are from memory. It's more qualative comparison than quantitive. -- Craig

2011-02-20, 16:24	#4
ixfd64 Bemusing Prompter "Danny" Dec 2002 California 2,341 Posts	I'm using 384 MB per core.