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Old 2016-03-04, 04:09   #1
Bemusing Prompter
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Dec 2002

237610 Posts
Default discrepancy in credit calculator for LL tests?

It is my understanding that double an exponent results in an LL test taking approximately four times longer.

From the CPU credit calculator, the 49th known Mersenne prime, M74,207,281, takes around 205 GHz-days. The first Mersenne number of prime index with 100 million digits, M332,192,831, needs around 4,941 GHz-days. This also seems reasonable. M601,248,421, the largest Mersenne number with an LL test to date, requires about 16,584 GHz-days, which closely matches the credit that Never Odd or Even received.

However, the numbers become weird after that: the calculator says the first Mersenne number with more than a billion digits, M3,321,928,097, requires just 91,630 GHz-days. The actual value should also be much higher; (3,321,928,097 / 601,248,421)2 ≈ 30.5, and multiplying that by 16,584 gives over 500,000 GHz-days.

So does the time complexity for LL tests stop exhibiting quadratic growth after a certain point? Or is there an error in the calculator?

Last fiddled with by ixfd64 on 2016-03-04 at 04:16
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