Talk:Lucas-Lehmer test: Difference between revisions
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== M<small><sub>23,209</sub></small> is 36 CPU hours ≡ 1979 == |
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Welcome to 1979! |
Welcome to 1979! |
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:Yeah. I know. :-) --[[User:Short Circuit|Short Circuit]] 07:55, 21 February 2008 (MST) |
:Yeah. I know. :-) --[[User:Short Circuit|Short Circuit]] 07:55, 21 February 2008 (MST) |
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==List of known Mersenne primes== |
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The table below lists all known Mersenne primes: |
The table below lists all known Mersenne primes: |
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{| class="wikitable" |
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== Java precision == |
== Java precision == |
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The Java version is still limited by types. Integer.parseInt(args[0]) limits p to 2147483647. Also the fact that isMersennePrime takes an int limits it there too. For full arbitrary precision every int needs to be a BigInteger or BigDecimal and a square root method will need to be created for them. The limitation is OK I think (I don't think we'll be getting up to 2<sup>2147483647</sup> - 1 anytime soon), but the claim "any arbitrary prime" is false because of the use of ints. --[[User:Mwn3d|Mwn3d]] 07:45, 21 February 2008 (MST) |
The Java version is still limited by types. Integer.parseInt(args[0]) limits p to 2147483647. Also the fact that isMersennePrime takes an int limits it there too. For full arbitrary precision every int needs to be a BigInteger or BigDecimal and a square root method will need to be created for them. The limitation is OK I think (I don't think we'll be getting up to 2<sup>2147483647</sup> - 1 anytime soon), but the claim "any arbitrary prime" is false because of the use of ints. --[[User:Mwn3d|Mwn3d]] 07:45, 21 February 2008 (MST) |
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== Speeding things up == |
== Speeding things up == |
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The main loop in Lucas-Lehmer is doing (n*n) mod M where M=2^p-1, and p > 1. '''But we can do it without division'''. |
The main loop in Lucas-Lehmer is doing (n*n) mod M where M=2^p-1, and p > 1. '''But we can do it without division'''. |
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