Mersenne primes

Mersenne primes is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Mersenne primes:

Challenge:

Create code that will list all of the Mersenne primes until some limitation is reached. For information on what a Mersenne prime is, go to this link: [[1]]

AppleScript

<lang> on isPrime(integ) set isComposite to "" if (integ / 2) = (integ / 2 div 1) then log integ & " is composite because 2 is a factor" as string --buttons {"OK", "Cancel"} default button 1 cancel button 2

else set x to 2 set sqrtOfInteg to integ ^ 0.5 repeat until x = integ ^ 0.5 + 1 as integer if (integ / x) = integ / x div 1 then log integ & " is composite because " & x & " & " & (integ / x div 1) & " are factors" as string --buttons {"OK", "Cancel"} default button 1 cancel button 2 set isComposite to 1 set x to x + 1 else

set x to x + 1 end if

end repeat log integ & " is prime" as string --buttons {"OK", "Cancel"} default button 1 cancel button 2 if isComposite = 1 then log integ & "is composite" else display dialog integ end if end if

end isPrime set x to 2 repeat isPrime(((2 ^ x) - 1) div 1) set x to x + 1 end repeat </lang>

D

Simplest thing that could possibly work. Using better primality tests will allow for more results to be calculated in a reasonable amount of time. <lang D>import std.bigint; import std.stdio;

bool isPrime(BigInt bi) {

   if (bi < 2) return false;
   if (bi % 2 == 0) return bi == 2;
   if (bi % 3 == 0) return bi == 3;
   
   auto test = BigInt(5);
   while (test * test < bi) {
       if (bi % test == 0) return false;
       test += 2;
       if (bi % test == 0) return false;
       test += 4;
   }

   return true;

}

void main() {

   auto base = BigInt(2);

   for (int pow=1; pow<32; pow++) {
       if (isPrime(base-1)) {
           writeln("2 ^ ", pow, " - 1");
       }
       base *= 2;
   }

}</lang>

Output:

2 ^ 2 - 1
2 ^ 3 - 1
2 ^ 5 - 1
2 ^ 7 - 1
2 ^ 13 - 1
2 ^ 17 - 1
2 ^ 19 - 1
2 ^ 31 - 1

Kotlin

This task is similar to the Lucas-Lehmer test task except that you can use whatever method you like to test the primality of the Mersenne numbers. Here, I've chosen to use the JDK's BigInteger.isProbablePrime(certainty) method. The exact algorithm is implementation dependent --- GNU classpath uses only Miller-Rabin, while Oracle JDK uses Miller-Rabin and sometimes adds a Lucas test (this is not the Lucas-Lehmer test).

A 'certainty' parameter of 10 is enough to find the first 20 Mersenne primes but as even this takes about 90 seconds on my modest machine I've not bothered going beyond that. <lang scala>// version 1.2.10

import java.math.BigInteger

const val MAX = 20

val bigOne = BigInteger.ONE val bigTwo = 2.toBigInteger()

/* for checking 'small' primes */ fun isPrime(n: Int): Boolean {

   if (n < 2) return false
   if (n % 2 == 0) return n == 2
   if (n % 3 == 0) return n == 3
   var d : Int = 5
   while (d * d <= n) {
       if (n % d == 0) return false
       d += 2
       if (n % d == 0) return false
       d += 4
   }
   return true

}

fun main(args: Array<String>) {

   var count = 0
   var p = 2
   while (true) {
       val m = (bigTwo shl (p - 1)) - bigOne
       if (m.isProbablePrime(10)) {
           println("2 ^ $p - 1")
           if (++count == MAX) break
       }
       // obtain next prime, p
       while(true) {
           p = if (p > 2) p + 2 else 3
           if (isPrime(p)) break
       }
   }

}</lang>

Output:

2 ^ 2 - 1
2 ^ 3 - 1
2 ^ 5 - 1
2 ^ 7 - 1
2 ^ 13 - 1
2 ^ 17 - 1
2 ^ 19 - 1
2 ^ 31 - 1
2 ^ 61 - 1
2 ^ 89 - 1
2 ^ 107 - 1
2 ^ 127 - 1
2 ^ 521 - 1
2 ^ 607 - 1
2 ^ 1279 - 1
2 ^ 2203 - 1
2 ^ 2281 - 1
2 ^ 3217 - 1
2 ^ 4253 - 1
2 ^ 4423 - 1

Perl

Since GIMPS went to the trouble of dedicating thousands of CPU years to finding Mersenne primes, we should be kind enough to use the results. The ntheory module front end does this, so the results up to 43 million is extremely fast (4 seconds), and we can reduce this another 10x by only checking primes. After the GIMPS double-checked mark, a Lucas-Lehmer test is done using code similar to Rosetta Code Lucas-Lehmer in C+GMP.

If this is too contrived, we can use Math::Prime::Util::GMP::is_mersenne_prime instead, which will run the Lucas-Lehmer test on each input. The first 23 Mersenne primes are found in under 15 seconds.

Library: ntheory

<lang perl>use ntheory qw/forprimes is_mersenne_prime/; forprimes { is_mersenne_prime($_) && say } 1e9;</lang>

Output:

2
3
5
7
13
17
19
31
61
...

Ring

<lang ring>

1. Project : Mersenne primes
2. Date  : 2018/01/22
3. Author : Gal Zsolt [~ CalmoSoft ~]
4. Email  : <calmosoft@gmail.com>

n = 0 while true

       n = n +1
       if isprime(pow(2,n)-1) = 1
          see n + nl
       ok

end

func isprime num

      if (num <= 1) return 0 ok
      if (num % 2 = 0) and num != 2 return 0 ok
      for i = 3 to floor(num / 2) -1 step 2
           if (num % i = 0) return 0 ok
      next
      return 1

</lang> Output:

2
3
5
7
13
17
19

zkl

Uses libGMP (GNU MP Bignum Library) and its Miller-Rabin probabilistic primality testing algorithm. <lang zkl>var [const] BN=Import("zklBigNum"); // libGMP fcn mprimes{

  n,m := BN(2),0;
  foreach e in ([2..]){
     n,m = n.shiftLeft(1), n-1;
     if(m.probablyPrime()) println("2^%d - 1".fmt(e));
  }

}() // gets rather slow after M(4423)</lang>

Output:

2^2 - 1
2^3 - 1
2^5 - 1
2^7 - 1
2^13 - 1
2^17 - 1
2^19 - 1
2^31 - 1
2^61 - 1
2^89 - 1
2^107 - 1
2^127 - 1
2^521 - 1
2^607 - 1
2^1279 - 1
2^2203 - 1
2^2281 - 1
2^3217 - 1
2^4253 - 1
2^4423 - 1
2^9689 - 1
2^9941 - 1
2^11213 - 1
...