Lucas-Lehmer test

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Task
Lucas-Lehmer test
You are encouraged to solve this task according to the task description, using any language you may know.

Lucas-Lehmer Test: for p an odd prime, the Mersenne number 2p − 1 is prime if and only if 2p − 1 divides S(p − 1) where S(n + 1) = (S(n))2 − 2, and S(1) = 4.

The following programs calculate all Mersenne primes up to the implementation's maximum precision, or the 47th Mersenne prime. (Which ever comes first).

Contents

[edit] 360 Assembly

For maximum compatibility, this program uses only the basic instruction set.

*        Lucas-Lehmer test
LUCASLEH CSECT
USING LUCASLEH,R12
SAVEARA B STM-SAVEARA(R15)
DC 17F'0'
DC CL8'LUCASLEH'
STM STM R14,R12,12(R13) save calling context
ST R13,4(R15)
ST R15,8(R13)
LR R12,R15 set addessability
* ---- CODE
LA R2,2 R2=2
LA R11,0 R11:N'
BCTR R11,0 N':=X'FFFFFFFF'
LA R10,1 R10:N N=1
LA R4,1 R4:IEXP
LA R6,1 step
LH R7,IEXPMAX R7:IEXPMAX limit
LOOPE BXH R4,R6,ENDLOOPE do iexp=2 to iexpmax
SR R3,R3 R3:S S=0
CR R4,R2 if iexp=2 then S=0
BE OKS
LA R3,4 else S=4
OKS EQU *
SLDA R10,1 n=(n+1)*2-1
LA R5,0 I
LA R8,1 step
LR R9,R4 IEXP
SR R9,R2 IEXP-2 limit
LOOPI BXH R5,R8,ENDLOOPI do i=1 to iexp-2
* ---- compute s=(s*s-2) MOD n
SR R14,R14 R14=0
LR R15,R3 R15=S
MR R14,R3 R{14-15}=S*S
SLR R15,R2 R15=R15-2=S*S-2
BNM *+6 skip next if no borrow
BCTR R14,0 perform borrow
DR R14,R10 R10=N
LR R3,R14 R14=MOD
B LOOPI
ENDLOOPI EQU *
LTR R3,R3
BNZ NOPRT if s<>0 then no print
CVD R4,P store to packed P
UNPK Z,P Z=P
MVC C,Z C=Z
OI C+L'C-1,X'F0' zap sign
MVC WTOBUF(4),C+12
MVI WTOBUF,C'M'
WTO MF=(E,WTOMSG)
NOPRT EQU *
B LOOPE
ENDLOOPE EQU *
* ---- END CODE
RETURN EQU *
LM R14,R12,12(R13)
XR R15,R15
BR R14
* ---- DATA
IEXPMAX DC H'31'
I DS H
IEXP DS H
S DS F
N DS F
P DS PL8 packed
Z DS ZL16 zoned
C DS CL16 character
WTOMSG DS 0F
DC H'80',XL2'0000'
WTOBUF DC 80C' '
LTORG
YREGS
END LUCASLEH
Output:
M002
M003
M005
M007
M013
M017
M019
M031

[edit] Ada

with Ada.Text_Io; use Ada.Text_Io;
with Ada.Integer_Text_Io; use Ada.Integer_Text_Io;
 
procedure Lucas_Lehmer_Test is
type Ull is mod 2**64;
function Mersenne(Item : Integer) return Boolean is
S : Ull := 4;
MP : Ull := 2**Item - 1;
begin
if Item = 2 then
return True;
else
for I in 3..Item loop
S := (S * S - 2) mod MP;
end loop;
return S = 0;
end if;
end Mersenne;
Upper_Bound : constant Integer := 64;
begin
Put_Line(" Mersenne primes:");
for P in 2..Upper_Bound loop
if Mersenne(P) then
Put(" M");
Put(Item => P, Width => 1);
end if;
end loop;
end Lucas_Lehmer_Test;
Output:
Mersenne primes:
M2 M3 M5 M7 M13 M17 M19 M31

[edit] Agena

Because of the very large numbers computed, the mapm binding is used to calculate with arbitrary precision.

readlib 'mapm';
 
mapm.xdigits(100);
 
mersenne := proc(p::number) is
local s, m;
s := 4;
m := mapm.xnumber(2^p) - 1;
if p = 2 then
return true
else
for i from 3 to p do
s := (mapm.xnumber(s)^2 - 2) % m
od;
return mapm.xtoNumber(s) = 0
fi
end;
 
for i from 3 to 64 do
if mersenne(i) then
write('M' & i & ' ')
fi
od;

produces:

M3 M5 M7 M13 M17 M19 M31

[edit] ALGOL 68

Works with: ALGOL 68 version Revision 1 - no extensions to language used
Works with: ALGOL 68G version Any - tested with release 1.18.0-9h.tiny
PRAGMAT stack=1M precision=20000 PRAGMAT
 
PROC is prime = ( INT p )BOOL:
IF p = 2 THEN TRUE
ELIF p <= 1 OR p MOD 2 = 0 THEN FALSE
ELSE
BOOL prime := TRUE;
FOR i FROM 3 BY 2 TO ENTIER sqrt(p)
WHILE prime := p MOD i /= 0 DO SKIP OD;
prime
FI;
 
PROC is mersenne prime = ( INT p )BOOL:
IF p = 2 THEN TRUE
ELSE
LONG LONG INT m p := LONG LONG 2 ** p - 1, s := 4;
FROM 3 TO p DO
s := (s ** 2 - 2) MOD m p
OD;
s = 0
FI;
 
test:(
INT upb prime = ( long long bits width - 1 ) OVER 2; # no unsigned #
INT upb count = 45; # find 45 mprimes if INT has enough bits #
 
printf(($" Finding Mersenne primes in M[2.."g(0)"]: "l$,upb prime));
 
INT count:=0;
FOR p FROM 2 TO upb prime WHILE
IF is prime(p) THEN
IF is mersenne prime(p) THEN
printf (($" M"g(0)$,p));
count +:= 1
FI
FI;
count <= upb count
DO SKIP OD
)
Output:
Finding Mersenne primes in M[2..33252]: 
M2 M3 M5 M7 M13 M17 M19 M31 M61 M89 M107 M127 M521 M607 M1279 M2203 M2281 M3217 M4253 M4423 M9689 M9941 M11213 M19937 M21701 M23209

See also: http://www.xs4all.nl/~jmvdveer/mersenne.a68.html

[edit] AWK

 
# syntax: GAWK -f LUCAS-LEHMER_TEST.AWK
# converted from Pascal
BEGIN {
printf("Mersenne primes:")
n = 1
for (exponent=2; exponent<=32; exponent++) {
s = (exponent == 2) ? 0 : 4
n = (n+1)*2-1
for (i=1; i<=exponent-2; i++) {
s = (s*s-2)%n
}
if (s == 0) {
printf(" M%s",exponent)
}
}
printf("\n")
exit(0)
}
 
Output:
Mersenne primes: M2 M3 M5 M7 M13 M17 M19

[edit] BBC BASIC

Using its native arithmetic BBC BASIC can only test up to M23.

      *FLOAT 64
PRINT "Mersenne Primes:"
FOR p% = 2 TO 23
IF FNlucas_lehmer(p%) PRINT "M" ; p%
NEXT
END
 
DEF FNlucas_lehmer(p%)
LOCAL i%, mp, sn
IF p% = 2 THEN = TRUE
IF (p% AND 1) = 0 THEN = FALSE
mp = 2^p% - 1
sn = 4
FOR i% = 3 TO p%
sn = sn^2 - 2
sn -= (mp * INT(sn / mp))
NEXT
= (sn = 0)
Output:
Mersenne Primes:
M2
M3
M5
M7
M13
M17
M19

[edit] Bracmat

Only exponents that are prime are tried. The primality test of these numbers uses a side effect of Bracmat's attempt at computing a root of a small enough number. ('small enough' meaning that the number must fit in a computer word, normally 32 or 64 bits.) To do that, Bracmat first creates a list of factors of the number and then takes the root of each factor. For example, to compute 54^2/3, Bracmat first creates the expression (2*3^3)^2/3 and then 2^2/3*3^(3*2/3), which becomes 2^2/3*9. If a number cannot be factorized, (either because it is prime or because it is to great to fit in a computer word) the root expression doesn't change much. For example, the expression 13^(13^-1) becomes 13^1/13, and this matches the pattern 13^%.

  ( clk$:?t0:?now
& ( time
= ( print
=
. put
$ ( str
$ ( div$(!arg,1)
","
( div$(mod$(!arg*100,100),1):?arg
& !arg:<10
& 0
|
)
 !arg
" "
)
)
)
& -1*!now+(clk$:?now):?SEC
& print$!SEC
& print$(!now+-1*!t0)
& put$"s: "
)
& 3:?exponent
& whl
' ( !exponent:~>12000
& (  !exponent^(!exponent^-1):!exponent^%
& 4:?s
& 2^!exponent+-1:?n
& 0:?i
& whl
' ( 1+!i:?i
& !exponent+-2:~<!i
& mod$(!s^2+-2.!n):?s
)
& (  !s:0
& !time
& out$(str$(M !exponent " is PRIME!"))
|
)
|
)
& 1+!exponent:?exponent
)
& done
);
Output:
(after 4.5 hours):
0,00 0,00 s: M3 is PRIME!
0,00 0,00 s: M5 is PRIME!
0,00 0,00 s: M7 is PRIME!
0,00 0,00 s: M13 is PRIME!
0,00 0,00 s: M17 is PRIME!
0,00 0,01 s: M19 is PRIME!
0,00 0,01 s: M31 is PRIME!
0,00 0,01 s: M61 is PRIME!
0,01 0,02 s: M89 is PRIME!
0,01 0,03 s: M107 is PRIME!
0,00 0,04 s: M127 is PRIME!
0,50 0,54 s: M521 is PRIME!
0,29 0,84 s: M607 is PRIME!
6,81 7,65 s: M1279 is PRIME!
38,35 46,01 s: M2203 is PRIME!
6,32 52,33 s: M2281 is PRIME!
116,01 168,34 s: M3217 is PRIME!
293,09 461,44 s: M4253 is PRIME!
64,61 526,05 s: M4423 is PRIME!
8863,90 9389,95 s: M9689 is PRIME!
1101,12 10491,08 s: M9941 is PRIME!
5618,45 16109,53 s: M11213 is PRIME!

[edit] C

[edit] GMP

This uses some pre-tests to show how we can skip some numbers with relatively inexpensive methods. This also does a simple optimization of the modulus. It takes about 30 seconds to get to M11213. This is substantially faster than many of the other solutions, though certainly not comparable to dedicated programs such as Prime95.

Takes an optional argument to test up to the given value.

Library: GMP
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <gmp.h>
 
int lucas_lehmer(unsigned long p)
{
mpz_t V, mp, t;
unsigned long k, tlim;
int res;
 
if (p == 2) return 1;
if (!(p&1)) return 0;
 
mpz_init_set_ui(t, p);
if (!mpz_probab_prime_p(t, 25)) /* if p is composite, 2^p-1 is not prime */
{ mpz_clear(t); return 0; }
 
if (p < 23) /* trust the PRP test for these values */
{ mpz_clear(t); return (p != 11); }
 
mpz_init(mp);
mpz_setbit(mp, p);
mpz_sub_ui(mp, mp, 1);
 
/* If p=3 mod 4 and p,2p+1 both prime, then 2p+1 | 2^p-1. Cheap test. */
if (p > 3 && p % 4 == 3) {
mpz_mul_ui(t, t, 2);
mpz_add_ui(t, t, 1);
if (mpz_probab_prime_p(t,25) && mpz_divisible_p(mp, t))
{ mpz_clear(mp); mpz_clear(t); return 0; }
}
 
/* Do a little trial division first. Saves quite a bit of time. */
tlim = p/2;
if (tlim > (ULONG_MAX/(2*p)))
tlim = ULONG_MAX/(2*p);
for (k = 1; k < tlim; k++) {
unsigned long q = 2*p*k+1;
/* factor must be 1 or 7 mod 8 and a prime */
if ( (q%8==1 || q%8==7) &&
q % 3 && q % 5 && q % 7 &&
mpz_divisible_ui_p(mp, q) )
{ mpz_clear(mp); mpz_clear(t); return 0; }
}
 
mpz_init_set_ui(V, 4);
for (k = 3; k <= p; k++) {
mpz_mul(V, V, V);
mpz_sub_ui(V, V, 2);
/* mpz_mod(V, V, mp) but more efficiently done given mod 2^p-1 */
if (mpz_sgn(V) < 0) mpz_add(V, V, mp);
/* while (n > mp) { n = (n >> p) + (n & mp) } if (n==mp) n=0 */
/* but in this case we can have at most one loop plus a carry */
mpz_tdiv_r_2exp(t, V, p);
mpz_tdiv_q_2exp(V, V, p);
mpz_add(V, V, t);
while (mpz_cmp(V, mp) >= 0) mpz_sub(V, V, mp);
}
res = !mpz_sgn(V);
mpz_clear(t); mpz_clear(mp); mpz_clear(V);
return res;
}
 
int main(int argc, char* argv[]) {
unsigned long i, n = 43112609;
if (argc >= 2) n = strtoul(argv[1], 0, 10);
for (i = 1; i <= n; i++) {
if (lucas_lehmer(i)) {
printf("M%lu ", i);
fflush(stdout);
}
}
printf("\n");
return 0;
}
Output:

(partial output after 50 minutes)

M2 M3 M5 M7 M13 M17 M19 M31 M61 M89 M107 M127 M521 M607 M1279 M2203 M2281 M3217 M4253 M4423 M9689 M9941 M11213 M11213 M19937 M21701 M23209 M44497 

[edit] Small inputs with native types

Works with: gcc version 4.1.2 20070925 (Red Hat 4.1.2-27)
Works with: C99

Compiler options: gcc -std=c99 -lm Lucas-Lehmer_test.c -o Lucas-Lehmer_test

#include <math.h>
#include <stdio.h>
#include <limits.h>
#pragma precision=log10l(ULLONG_MAX)/2
 
typedef enum { FALSE=0, TRUE=1 } BOOL;
 
BOOL is_prime( int p ){
if( p == 2 ) return TRUE;
else if( p <= 1 || p % 2 == 0 ) return FALSE;
else {
BOOL prime = TRUE;
const int to = sqrt(p);
int i;
for(i = 3; i <= to; i+=2)
if (!(prime = p % i))break;
return prime;
}
}
 
BOOL is_mersenne_prime( int p ){
if( p == 2 ) return TRUE;
else {
const long long unsigned m_p = ( 1LLU << p ) - 1;
long long unsigned s = 4;
int i;
for (i = 3; i <= p; i++){
s = (s * s - 2) % m_p;
}
return s == 0;
}
}
 
int main(int argc, char **argv){
 
const int upb = log2l(ULLONG_MAX)/2;
int p;
printf(" Mersenne primes:\n");
for( p = 2; p <= upb; p += 1 ){
if( is_prime(p) && is_mersenne_prime(p) ){
printf (" M%u",p);
}
}
printf("\n");
}
Output:
 Mersenne primes:
 M2 M3 M5 M7 M13 M17 M19 M31

[edit] C++

Straightforward method.

Library: GMP
#include <iostream>
#include <gmpxx.h>
 
static bool is_mersenne_prime(mpz_class p)
{
if( 2 == p )
return true;
else
{
mpz_class s(4);
mpz_class div( (mpz_class(1) << p.get_ui()) - 1 );
for( mpz_class i(3); i <= p; ++i )
{
s = (s * s - mpz_class(2)) % div ;
}
 
return ( s == mpz_class(0) );
}
}
 
int main()
{
mpz_class maxcount(45);
mpz_class found(0);
mpz_class check(0);
for( mpz_nextprime(check.get_mpz_t(), check.get_mpz_t());
found < maxcount;
mpz_nextprime(check.get_mpz_t(), check.get_mpz_t()))
{
//std::cout << "P" << check << " " << std::flush;
if( is_mersenne_prime(check) )
{
++found;
std::cout << "M" << check << " " << std::flush;
}
}
}
Output:
(Incomplete; It takes a long time.)
 M2 M3 M5 M7 M13 M17 M19 M31 M61 M89 M107 M127 M521 M607 M1279 M2203 M2281 M3217 M4253 M4423 M9689 M9941 M11213 M19937 M21701 M23209 M44497

[edit] C#

Works with: Visual Studio version 2010
Works with: .NET Framework version 4.0
using System;
using System.Collections.Generic;
using System.Numerics;
using System.Threading.Tasks;
 
namespace LucasLehmerTestForRosettaCode
{
public class LucasLehmerTest
{
static BigInteger ZERO = new BigInteger(0);
static BigInteger ONE = new BigInteger(1);
static BigInteger TWO = new BigInteger(2);
static BigInteger FOUR = new BigInteger(4);
 
private static bool isMersennePrime(int p)
{
if (p % 2 == 0) return (p == 2);
else {
for (int i = 3; i <= (int)Math.Sqrt(p); i += 2)
if (p % i == 0) return false; //not prime
BigInteger m_p = BigInteger.Pow(TWO, p) - ONE;
BigInteger s = FOUR;
for (int i = 3; i <= p; i++)
s = (s * s - TWO) % m_p;
return s == ZERO;
}
}
 
public static int[] GetMersennePrimeNumbers(int upTo)
{
List<int> response = new List<int>();
Parallel.For(2, upTo, i => {
if (isMersennePrime(i)) response.Add(i);
});
response.Sort();
return response.ToArray();
}
 
static void Main(string[] args)
{
int[] mersennePrimes = LucasLehmerTest.GetMersennePrimeNumbers(11213);
foreach (int mp in mersennePrimes)
Console.Write("M" + mp+" ");
Console.ReadLine();
}
}
}
Output:
(Run only to 11213)
 M2 M3 M5 M7 M13 M17 M19 M31 M61 M89 M107 M127 M521 M607 M1279 M2203 M2281 M3217 M4253 M4423 M9689 M9941 M11213

[edit] Clojure

(defn prime? [i]
(cond (< i 4) (>= i 2)
(zero? (rem i 2)) false
:else (not-any? #(zero? (rem i %)) (range 3 (inc (Math/sqrt i))))))))
 
(defn mersenne? [p] (or (= p 2)
(let [mp (dec (bit-shift-left 1 p))]
(loop [n 3 s 4]
(if (> n p)
(zero? s)
(recur (inc n) (rem (- (* s s) 2) mp)))))))
 
(filter mersenne? (filter prime? (iterate inc 1)))
Output:
 Infinite list of Mersenne primes:
 (2 3 5 7 13 17 19 31 61 89 107 127 521 607 1279 2203 2281 3217 4253...

[edit] D

Translation of: Python
import std.stdio, std.math, std.bigint;
 
bool isPrime(in uint p) pure nothrow @safe @nogc {
if (p < 2 || p % 2 == 0)
return p == 2;
foreach (immutable i; 3 .. cast(uint)real(p).sqrt + 1)
if (p % i == 0)
return false;
return true;
}
 
bool isMersennePrime(in uint p) pure nothrow /*@safe*/ {
if (!p.isPrime)
return false;
if (p == 2)
return true;
immutable mp = (1.BigInt << p) - 1;
auto s = 4.BigInt;
foreach (immutable _; 3 .. p + 1)
s = (s ^^ 2 - 2) % mp;
return s == 0;
}
 
void main() {
foreach (immutable p; 2 .. 2_300)
if (p.isMersennePrime) {
write('M', p, ' ');
stdout.flush;
}
}
Output:
M2 M3 M5 M7 M13 M17 M19 M31 M61 M89 M107 M127 M521 M607 M1279 M2203 M2281 

With p up to 10_000 it prints:

M2 M3 M5 M7 M13 M17 M19 M31 M61 M89 M107 M127 M521 M607 M1279 M2203 M2281 M3217 M4253 M4423 M9941 

[edit] DWScript

Using Integer type, which is 64bit, limits the search to M31.

function IsMersennePrime(p : Integer) : Boolean;
var
i, s, m_p : Integer;
begin
if p=2 then
Result:=True
else begin
m_p := (1 shl p)-1;
s := 4;
for i:=3 to p do
s:=(s*s-2) mod m_p;
Result:=(s=0);
end;
end;
 
const upperBound = Round(Log2(High(Integer))/2);
 
PrintLn('Finding Mersenne primes in M[2..' + IntToStr(upperBound) + ']: ');
Print('M2');
 
var p : Integer;
for p:=3 to upperBound step 2 do begin
if IsMersennePrime(p) then
Print(' M'+IntToStr(p));
end;
PrintLn('');
Output:
 M2 M3 M5 M7 M13 M17 M19 M31

[edit] Erlang

-module(mp).
-export([main/0]).
 
main() -> [ io:format("M~p ", [P]) || P <- lists:seq(2,700), (P == 2) orelse (s((1 bsl P) - 1, P-1) == 0) ].
 
s(MP,1) -> 4 rem MP;
s(MP,N) -> X=s(MP,N-1), (X*X - 2) rem MP.

In 3 seconds will print

M2 M3 M5 M7 M13 M17 M19 M31 M61 M89 M107 M127 M521 M607

Testing larger numbers (i.e. 5000) is possible but will take few minutes.

[edit] F#

Simple arbitrary-precision version:

let rec s mp n =
if n = 1 then 4I % mp else ((s mp (n - 1)) ** 2 - 2I) % mp
 
[ for p in 2..47 do
if p = 2 || s ((1I <<< p) - 1I) (p - 1) = 0I then
yield p ]

Tail-recursive version:

let IsMersennePrime exponent =
if exponent <= 1 then failwith "Exponent must be >= 2"
let prime = 2I ** exponent - 1I;
 
let rec LucasLehmer i acc =
match i with
| x when x = exponent - 2 -> acc
| x -> LucasLehmer (x + 1) ((acc*acc - 2I) % prime)
 
LucasLehmer 0 4I = 0I
 

Version using library folding function (way shorter and faster than the above):

let IsMersennePrime exponent =
if exponent <= 1 then failwith "Exponent must be >= 2"
let prime = 2I ** exponent - 1I;
 
let LucasLehmer =
[| 1 .. exponent-2 |] |> Array.fold (fun acc _ -> (acc*acc - 2I) % prime) 4I
 
LucasLehmer = 0I
 

[edit] Fortran

Works with: Fortran version 90 and later

Only Mersenne number with prime exponent can be themselves prime but for the small numbers used in this example it was not worth the effort to include this check. As the size of the exponent increases this becomes more important.

PROGRAM LUCAS_LEHMER
IMPLICIT NONE
 
INTEGER, PARAMETER :: i64 = SELECTED_INT_KIND(18)
INTEGER(i64) :: s, n
INTEGER :: i, exponent
 
DO exponent = 2, 31
IF (exponent == 2) THEN
s = 0
ELSE
s = 4
END IF
n = 2_i64**exponent - 1
DO i = 1, exponent-2
s = MOD(s*s - 2, n)
END DO
IF (s==0) WRITE(*,"(A,I0,A)") "M", exponent, " is PRIME"
END DO
 
END PROGRAM LUCAS_LEHMER

[edit] FunL

def mersenne( p ) =
if p == 2 then return true
 
var s = 4
var M = 2^p - 1
 
repeat p - 2
s = (s*s - 2) mod M
 
s == 0
 
import integers.primes
 
for p <- primes().filter( mersenne ).take( 20 )
println( 'M' + p )
Output:
M2
M3
M5
M7
M13
M17
M19
M31
M61
M89
M107
M127
M521
M607
M1279
M2203
M2281
M3217
M4253
M4423

[edit] GAP

LucasLehmer := function(n)
local i, m, s;
if n = 2 then
return true;
elif not IsPrime(n) then
return false;
else
m := 2^n - 1;
s := 4;
for i in [3 .. n] do
s := RemInt(s*s, m) - 2;
od;
return s = 0;
fi;
end;
 
Filtered([1 .. 2000], LucasLehmer);
[2, 3, 5, 7, 13, 17, 19, 31, 61, 89, 107, 127, 521, 607, 1279]

[edit] Go

Processing the first list indicates that the test works. Processing the second shows it working on some larger numbers.

package main
 
import (
"fmt"
"math/big"
)
 
var primes = []uint{3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47,
53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127}
 
var mersennes = []uint{521, 607, 1279, 2203, 2281, 3217, 4253, 4423, 9689,
9941, 11213, 19937, 21701, 23209, 44497, 86243, 110503, 132049, 216091,
756839, 859433, 1257787, 1398269, 2976221, 3021377, 6972593, 13466917,
20996011, 24036583}
 
func main() {
llTest(primes)
fmt.Println()
llTest(mersennes)
}
 
func llTest(ps []uint) {
var s, m big.Int
one := big.NewInt(1)
two := big.NewInt(2)
for _, p := range ps {
m.Sub(m.Lsh(one, p), one)
s.SetInt64(4)
for i := uint(2); i < p; i++ {
s.Mod(s.Sub(s.Mul(&s, &s), two), &m)
}
if s.BitLen() == 0 {
fmt.Printf("M%d ", p)
}
}
}
Output:
M3 M5 M7 M13 M17 M19 M31 M61 M89 M107 M127 
M521 M607 M1279 M2203 M2281 M3217 M4253 M4423 M9689 M9941 M11213 M19937...

[edit] Haskell

Works with: GHCi version 6.8.2
Works with: GHC version 6.8.2
module Main
where
 
main = printMersennes $ take 45 $ filter lucasLehmer $ sieve [2..]
 
s mp 1 = 4 `mod` mp
s mp n = ((s mp $ n-1)^2-2) `mod` mp
 
lucasLehmer 2 = True
lucasLehmer p = s (2^p-1) (p-1) == 0
 
printMersennes = mapM_ (\x -> putStrLn $ "M" ++ show x)

It is pointed out on the Sieve of Eratosthenes page that the following "sieve" is inefficient. Nonetheless it takes very little time compared to the Lucas-Lehmer test itself.

sieve (p:xs) = p : sieve [x | x <- xs, x `mod` p > 0]

It takes about 30 minutes to get up to:

M2 M3 M5 M7 M13 M17 M19 M31 M61 M89 M107 M127 M521 M607 M1279 M2203 M2281 M3217 M4253 M4423 M9689 M9941 M11213

[edit] HicEst

s = 0
DO exponent = 2, 31
IF(exponent > 2) s = 4
n = 2^exponent - 1
DO i = 1, exponent-2
s = MOD(s*s - 2, n)
ENDDO
IF(s == 0) WRITE(Messagebox) 'M', exponent, ' is prime;', n
ENDDO
 
END

[edit] J

See Primality Tests essay on the J wiki.

[edit] Java

We use arbitrary-precision integers in order to be able to test any arbitrary prime.

import java.math.BigInteger;
public class Mersenne
{
 
public static boolean isPrime(int p) {
if (p == 2)
return true;
else if (p <= 1 || p % 2 == 0)
return false;
else {
int to = (int)Math.sqrt(p);
for (int i = 3; i <= to; i += 2)
if (p % i == 0)
return false;
return true;
}
}
 
public static boolean isMersennePrime(int p) {
if (p == 2)
return true;
else {
BigInteger m_p = BigInteger.ONE.shiftLeft(p).subtract(BigInteger.ONE);
BigInteger s = BigInteger.valueOf(4);
for (int i = 3; i <= p; i++)
s = s.multiply(s).subtract(BigInteger.valueOf(2)).mod(m_p);
return s.equals(BigInteger.ZERO);
}
}
 
// an arbitrary upper bound can be given as an argument
public static void main(String[] args) {
int upb;
if (args.length == 0)
upb = 500;
else
upb = Integer.parseInt(args[0]);
 
System.out.print(" Finding Mersenne primes in M[2.." + upb + "]:\nM2 ");
for (int p = 3; p <= upb; p += 2)
if (isPrime(p) && isMersennePrime(p))
System.out.print(" M" + p);
System.out.println();
}
}
Output:
(after about eight hours):
 Finding Mersenne primes in M[2..2147483647]: 
 M2 M3 M5 M7 M13 M17 M19 M31 M61 M89 M107 M127 M521 M607 M1279 M2203 M2281 M3217 M4253 M4423 M9689 M9941 M11213

[edit] Mathematica

This version is very speedy and is bounded.

Select[Table[M = 2^p - 1; 
For[i = 1; s = 4, i <= p - 2, i++, s = Mod[s^2 - 2, M]];
If[s == 0, "M" <> ToString@p, p], {p,
Prime /@ Range[300]}], StringQ]
 
=> {M3, M5, M7, M13, M17, M19, M31, M61, M89, M107, M127, M521, M607, M1279}

This version is unbounded (and timed):

t = SessionTime[];
For[p = 2, True, p = NextPrime[p], M = 2^p - 1;
For[i = 1; s = 4, i <= p - 2, i++, s = Mod[s^2 - 2, M]];
If[s == 0, Print["M" <> ToString@p]]]
(SessionTime[] - t) {Seconds, Minutes/60, Hours/3600, Days/86400}

I'll see what this gets.

[edit] MATLAB

MATLAB suffers from a lack of an arbitrary precision math (bignums) library. It also doesn't have great support for 64-bit integer arithmetic...or at least MATLAB 2007 doesn't. So, the best precision we have is doubles; therefore, this script can only find up to M19 and no greater.

function [mNumber,mersennesPrime] = mersennePrimes()
 
function isPrime = lucasLehmerTest(thePrime)
 
llResidue = 4;
mersennesPrime = (2^thePrime)-1;
 
for i = ( 1:thePrime-2 )
llResidue = mod( ((llResidue^2) - 2),mersennesPrime );
end
 
isPrime = (llResidue == 0);
 
end
 
%Because IEEE764 Double is the highest precision number we can
%represent in MATLAB, the highest Mersenne Number we can test is 2^52.
%In addition, because we have this cap, we can only test up to the
%number 30 for Mersenne Primeness. When we input 31 into the
%Lucas-Lehmer test, during the computation of the residue, the
%algorithm multiplies two numbers together the result of which is
%greater than 2^53. Because we require every digit to be significant,
%this leads to an error. The Lucas-Lehmer test should say that M31 is a
%Mersenne Prime, but because of the rounding error in calculating the
%residues caused by floating-point arithmetic, it does not. So M30 is
%the largest number we test.
 
mNumber = (3:30);
 
[isPrime] = arrayfun(@lucasLehmerTest,mNumber);
 
mNumber = [2 mNumber(isPrime)];
mersennesPrime = (2.^mNumber) - 1;
 
end
Output:
[mNumber,mersennesPrime] = mersennePrimes
 
mNumber =
 
2 3 5 7 13 17 19
 
 
mersennesPrime =
 
3 7 31 127 8191 131071 524287

[edit] Maxima

lucas_lehmer(p) := block([s, n, i],
if not primep(p) then false elseif p = 2 then true else
(s: 4,
n: 2^p - 1,
for i: 2 thru p - 1 do s: mod(s*s - 2, n),
is(s = 0))
)$
 
sublist(makelist(i, i, 1, 200), lucas_lehmer);
/* [2, 3, 5, 7, 13, 17, 19, 31, 61, 89, 107, 127] */

[edit] Modula-3

Modula-3 uses L as the literal for LONGINT.

MODULE LucasLehmer EXPORTS Main;
 
IMPORT IO, Fmt, Long;
 
PROCEDURE Mersenne(p: CARDINAL): BOOLEAN =
VAR
s := 4L;
m := Long.Shift(1L, p) - 1L; (* 2^p - 1 *)
BEGIN
IF p = 2 THEN
RETURN TRUE;
ELSE
FOR i := 3 TO p DO
s := (s * s - 2L) MOD m;
END;
RETURN s = 0L;
END;
END Mersenne;
 
BEGIN
FOR i := 2 TO 63 DO
IF Mersenne(i) THEN
IO.Put("M" & Fmt.Int(i) & " ");
END;
END;
IO.Put("\n");
END LucasLehmer.
Output:
M2 M3 M5 M7 M13 M17 M19 M31 

[edit] Nimrod

import math
 
proc isPrime(a: int): bool =
if a == 2: return true
if a < 2 or a mod 2 == 0: return false
for i in countup(3, int sqrt(float a), 2):
if a mod i == 0:
return false
return true
 
proc isMersennePrime(p: int): bool =
if p == 2: return true
let mp = (1'i64 shl p) - 1
var s = 4'i64
for i in 3 .. p:
s = (s * s - 2) mod mp
result = s == 0
 
let upb = int((log2 float int64.high) / 2)
echo " Mersenne primes:"
for p in 2 .. upb:
if isPrime(p) and isMersennePrime(p):
stdout.write " M",p
echo ""
Output:
 Mersenne primes:
 M2 M3 M5 M7 M13 M17 M19 M31

[edit] Oz

Oz's multiple precision number system use GMP core.

%% compile : ozc -x <file.oz>
functor
import
Application
System
define
 
fun {Arg Idx Default}
Cmd = {Application.getArgs plain}
Len = {Length Cmd}
in
if Len < Idx then
Default
else
{StringToInt {Nth Cmd Idx}}
end
end
 
fun {LLtest N}
Mp = {Pow 2 N} - 1
fun {S K} X T
in
if K == 1 then 4
else
T = {S K-1}
X = T * T - 2
X mod Mp
end
end
in
if N == 2 then
true
else
{S N-1} == 0
end
end
 
proc {FindLL X}
fun {Sieve Ls}
case Ls of nil then nil
[] X|Xs then
fun {DIV M} M mod X \= 0 end
in
X|{Sieve {Filter Xs DIV}}
end
end
in
if {IsList X} then
case X of nil then skip
[] M|Ms then
{System.printInfo "M"#M#" "}
{FindLL Ms}
end
else
{FindLL {Filter {Sieve 2|{List.number 3 X 2}} LLtest}}
end
end
 
Num = {Arg 1 607}
 
{FindLL Num}
 
{Application.exit 0}
end

[edit] PARI/GP

LL(p)={
my(m=Mod(4,1<<p-1));
for(i=3,p,m=m^2-2);
m==0
};
 
search()={
my(t=1);
print("2^2-1");
forprime(p=3,43112609,
if(LL(p),
print("2^"p"-1");
if(t++==47,return())
)
)
};

[edit] Pascal

int64 is good enough up to M31:

Program LucasLehmer(output);
var
s, n: int64;
i, exponent: integer;
begin
n := 1;
for exponent := 2 to 31 do
begin
if exponent = 2 then
s := 0
else
s := 4;
n := (n + 1)*2 - 1; // This saves from needing the math unit for exponentiation
for i := 1 to exponent-2 do
s := (s*s - 2) mod n;
if s = 0 then
writeln('M', exponent, ' is PRIME!');
end;
end.
Output:
:> ./LucasLehmer
M2 is PRIME!
M3 is PRIME!
M5 is PRIME!
M7 is PRIME!
M13 is PRIME!
M17 is PRIME!
M19 is PRIME!
M31 is PRIME!

[edit] Perl

Using Math::GMP:

use Math::GMP qw/:constant/;
 
sub is_prime { Math::GMP->new(shift)->probab_prime(12); }
 
sub is_mersenne_prime {
my $p = shift;
return 1 if $p == 2;
my $mp = 2 ** $p - 1;
my $s = 4;
$s = ($s * $s - 2) % $mp for 3..$p;
$s == 0;
}
 
foreach my $p (2 .. 43_112_609) {
print "M$p\n" if is_prime($p) && is_mersenne_prime($p);
}

The ntheory module offers a couple options. This is direct:

Library: ntheory
use ntheory qw/:all/;
$|=1; # flush output on every print
my $n = 0;
for (1..47) {
1 while !is_mersenne_prime(++$n);
print "M$n ";
}
print "\n";

However it uses knowledge from the thousands of CPU years spent by GIMPS to accelerate results for known values, so doesn't actually run the L-L test until after the 44th value, although code is included for C, Perl, and C+GMP. If we substitute Math::Prime::Util::GMP::is_mersenne_prime we can force the test to run.

A less opaque method uses the modular Lucas sequence, though it has no pretesting other than primality and calculates both Uk and Vk so won't be as fast:

use ntheory qw/:all/;
use bigint try=>"GMP,Pari";
forprimes {
my $p = $_;
my $mp1 = 2**$p;
print "M$p\n" if $p == 2 || 0 == (lucas_sequence($mp1-1, 4, 1, $mp1))[0];
} 43_112_609;

We can also use the core module Math::BigInt:

Translation of: Python
sub is_prime {
my $p = shift;
if ($p == 2) {
return 1;
} elsif ($p <= 1 || $p % 2 == 0) {
return 0;
} else {
my $limit = sqrt($p);
for (my $i = 3; $i <= $limit; $i += 2) {
return 0 if $p % $i == 0;
}
return 1;
}
}
 
sub is_mersenne_prime {
use bigint;
my $p = shift;
if ($p == 2) {
return 1;
} else {
my $m_p = 2 ** $p - 1;
my $s = 4;
 
foreach my $i (3 .. $p) {
$s = ($s ** 2 - 2) % $m_p;
}
return $s == 0;
}
}
 
my $precision = 20000; # maximum requested number of decimal places of 2 ** MP-1 #
my $long_bits_width = $precision / log(2) * log(10);
my $upb_prime = int(($long_bits_width - 1)/2); # no unsigned #
my $upb_count = 45; # find 45 mprimes if int was given enough bits #
 
print " Finding Mersenne primes in M[2..$upb_prime]:\n";
 
my $count = 0;
foreach my $p (2 .. $upb_prime) {
if (is_prime($p) && is_mersenne_prime($p)) {
print "M$p\n";
$count++;
}
last if $count >= $upb_count;
}

[edit] Perl 6

multi is_mersenne_prime(2) { True }
multi is_mersenne_prime(Int $p) {
my $m_p = 2 ** $p - 1;
my $s = 4;
# Alternate but slightly slower: $s = ($s * $s - 2) % $m_p for 3..$p;
for (3 .. $p) {
$s = $s.expmod(2, $m_p) - 2;
$s += $m_p if $s < 0;
}
$s == 0;
}
 
say "M$_" if is-prime($_) and is_mersenne_prime($_) for 2..*;
Output:
M2
M3
M5
M7
M13
M17
M19
M31
M61
M89
M107
M127
M521
M607
M1279
M2203
M2281
M3217
M4253
M4423
^C

[edit] PicoLisp

(de prime? (N)
(or
(= N 2)
(and
(> N 1)
(bit? 1 N)
(for (D 3 T (+ D 2))
(T (> D (sqrt N)) T)
(T (=0 (% N D)) NIL) ) ) ) )
 
(de mersenne? (P)
(or
(= P 2)
(let (MP (dec (>> (- P) 1)) S 4)
(do (- P 2)
(setq S (% (- (* S S) 2) MP)) )
(=0 S) ) ) )
Output:
: (for N 10000
   (and (prime? N) (mersenne? N) (println N)) )
2
3
5
7
13
17
19
31
61
89
107
127
521
607
1279
2203
2281
3217
4253
4423
9689
9941

[edit] Pop11

Checking large numbers takes a lot of time so we limit p to be smaller than 1000.

define Lucas_Lehmer_Test(p);
lvars mp = 2**p - 1, sn = 4, i;
for i from 2 to p - 1 do
(sn*sn - 2) rem mp -> sn;
endfor;
sn = 0;
enddefine;
 
lvars p = 3;
printf('M2', '%p\n');
while p < 1000 do
if Lucas_Lehmer_Test(p) then
printf('M', '%p');
printf(p, '%p\n');
endif;
p + 2 -> p;
endwhile;
Output:
(obtained in few seconds)
M2
M3
M5
M7
M13
M17
M19
M31
M61
M89
M107
M127
M521
M607

[edit] PureBasic

PureBasic has no large integer support. Calculations are limited to the range of a signed quad integer type.

Procedure Lucas_Lehmer_Test(p)
Protected mp.q = (1 << p) - 1, sn.q = 4, i
For i = 3 To p
sn = (sn * sn - 2) % mp
Next
If sn = 0
ProcedureReturn #True
EndIf
ProcedureReturn #False
EndProcedure
 
#upperBound = SizeOf(Quad) * 8 - 1 ;equivalent to significant bits in a signed quad integer
If OpenConsole()
Define p = 3
PrintN("M2")
While p <= #upperBound
If Lucas_Lehmer_Test(p)
PrintN("M" + Str(p))
EndIf
p + 2
Wend
 
Print(#CRLF$ + #CRLF$ + "Press ENTER to exit"): Input()
CloseConsole()
EndIf
Output:
M2
M3
M5
M7
M13
M17
M19
M31

[edit] Python

from sys import stdout
from math import sqrt, log
 
def is_prime ( p ):
if p == 2: return True # Lucas-Lehmer test only works on odd primes
elif p <= 1 or p % 2 == 0: return False
else:
for i in range(3, int(sqrt(p))+1, 2 ):
if p % i == 0: return False
return True
 
def is_mersenne_prime ( p ):
if p == 2:
return True
else:
m_p = ( 1 << p ) - 1
s = 4
for i in range(3, p+1):
s = (s ** 2 - 2) % m_p
return s == 0
 
precision = 20000 # maximum requested number of decimal places of 2 ** MP-1 #
long_bits_width = precision * log(10, 2)
upb_prime = int( long_bits_width - 1 ) / 2 # no unsigned #
upb_count = 45 # find 45 mprimes if int was given enough bits #
 
print (" Finding Mersenne primes in M[2..%d]:"%upb_prime)
 
count=0
for p in range(2, upb_prime+1):
if is_prime(p) and is_mersenne_prime(p):
print("M%d"%p),
stdout.flush()
count += 1
if count >= upb_count: break
print
Output:
 Finding Mersenne primes in M[2..33218]: 
 M2 M3 M5 M7 M13 M17 M19 M31 M61 M89 M107 M127 M521 M607 M1279 M2203 M2281 M3217 M4253 M4423 M9689 M9941 M11213 M19937 M21701 M23209

[edit] Faster loop without division

def isqrt(n):
if n < 0:
raise ValueError
elif n < 2:
return n
else:
a = 1 << ((1 + n.bit_length()) >> 1)
while True:
b = (a + n // a) >> 1
if b >= a:
return a
a = b
 
def isprime(n):
if n < 5:
return n == 2 or n == 3
elif n%2 == 0:
return False
else:
r = isqrt(n)
k = 3
while k <= r:
if n%k == 0:
return False
k += 2
return True
 
def lucas_lehmer_fast(n):
if n == 2:
return True
elif not isprime(n):
return False
else:
m = 2**n - 1
s = 4
for i in range(2, n):
sqr = s*s
r = (sqr & m) + (sqr >> n)
if r >= m:
r -= m
s = r - 2
return s == 0

[edit] Racket

 
#lang racket
(require math)
 
(define (mersenne-prime? p)
(divides? (- (expt 2 p) 1) (S (- p 1))))
 
(define (S n)
(if (= n 1) 4 (- (sqr (S (- n 1))) 2)))
 
(define (loop p)
(when (mersenne-prime? p)
(displayln p))
(loop (next-prime p)))
 
(loop 3)
 

[edit] REXX

REXX won't have a problem with the large number of digits involved, but since it's an interpreted language,
such massive number crunching isn't conducive in searching for large primes.

/*REXX program to use Lucas-Lehmer primality test for prime powers of 2.*/
parse arg limit . /*get the optional arg from C.L. */
if limit=='' then limit=1000 /*No argument? Then assume 1000.*/
list= /*placeholder for the results. */
/* [↓] only process up to LIMIT,*/
do j=1 by 2 to limit /*···only so many hours in a day.*/
power=j + (j==1) /*POWER ≡ J except for when J=1.*/
if \isPrime(power) then iterate /*if not prime, then ignore it. */
list=list Lucas_Lehmer2(power) /*add to list (···or maybe not).*/
end /*j*/
 
list=space(list) /*remove all extraneous blanks. */
say; say center('list',60-3,"═") /*show a fancy-dancy header/title*/
say
do k=1 for words(list) /*show entries in list, 1/line. */
say right(word(list,k),30) /*right-justify 'em to look nice.*/
end /*k*/
exit /*stick a fork in it, we're done.*/
/*──────────────────────────────────ISPRIME subroutine──────────────────*/
isPrime: procedure; parse arg x /*get # to be tested*/
if x<17 then return wordpos(x,'2 3 5 7 11 13')\==0 /*test special cases*/
if x//2==0 then return 0 /*is it even? Not prime.*/
if x//3==0 then return 0 /*divisible by three? Not prime.*/
if right(x,1)==5 then return 0 /*right-most dig ≡ 5? Not prime.*/
if x//7==0 then return 0 /*divisible by seven? Not prime.*/
 
do j=11 by 6 until j*j>x /*ensures J isn't divisible by 3.*/
if x// j ==0 then return 0 /*is divisible by J  ? */
if x//(j+2)==0 then return 0 /* " " " J+2 ? ___*/
end /*j*/ /* [↑] perform loop through √ x */
return 1 /*indicate the number X is prime.*/
/*──────────────────────────────────LUCAS_LEHMER2 subroutine────────────*/
Lucas_Lehmer2: procedure; parse arg ? /*Lucas-Lehmer test on 2**? - 1 */
if form()\=='SCIENTIFIC' then numeric form /*ensure correct # form.*/
if ?==2 then s=0 /*handle the special even case.*/
else s=4
q=2**? /*╔═════════════════════════════════════════════════════════════╗
║Compute a power of 2, using only 9 decimal digits. DIGITs ║
║of 1 million could be used, but that really gums up the whole║
║works. So, we start with the default of 9 digits, find the ║
║ten's exponent in the product (2**?), double it, and then add║
║6. 2 is all that's needed, but 6 is a lot safer.║
║The doubling is for the squaring of S (below, for s*s).║
╚═════════════════════════════════════════════════════════════╝*/

if pos('E',q)\==0 then do /*is # in exponential notation?*/
parse var q 'E' tenpow
numeric digits tenpow*2 + 6
end
else numeric digits digits()*2 + 6 /* 9*2 + 6 */
q=2**?-1
do ?-2 /*apply, rinse, repeat ··· */
s=(s*s-2) // q /*remainder in REXX is: // */
end /* [↑] compute the real McCoy. */
 
if s\==0 then return '' /*return nuttin' if not prime. */
return 'M'? /*return modified (prime) number.*/
Output:
when the following is used for input:   10000
══════════════════════════list═══════════════════════════

                            M2
                            M3
                            M5
                            M7
                           M13
                           M17
                           M19
                           M31
                           M61
                           M89
                          M107
                          M127
                          M521
                          M607
                         M1279
                         M2203
                         M2281
                         M3217
                         M4253
                         M4423
                         M9689
                         M9941
On IBM VM and MVS Rexx programs can be compiled.
The above program uses (elapsed time) 
 interpreted      100   seconds
 compiled           1.5 seconds
 (for limit=2000)  20   seconds
--[[User:Walterpachl|Walterpachl]] 09:55, 12 July 2012 (UTC)

[edit] RPL

 
%%HP: T(3)A(R)F(.);  ; ASCII transfer header
\<< DUP LN DUP \pi * 4 SWAP / 1 + UNROT / * IP 2 { 2 } ROT 2 SWAP  ; input n; n := Int(n/ln(n)*(1 + 4/(pi*ln(n)))), p:=2; (n ~ number of primes less then n, pi used here only as a convenience), 2 is assumed to be the 1st elemente in the list
START SWAP NEXTPRIME DUP UNROT DUP 2 SWAP ^ 1 - 4 PICK3 2 - 1 SWAP  ; for i := 2 to n, p := nextprime; s := 4; m := 2^p - 1;
START SQ 2 - OVER MOD  ; for j := 1 to p - 2; s := s^2 mod m;
NEXT NIP NOT { + } { DROP } IFTE  ; next j; if s = 0 then add p to the list else discard p;
NEXT NIP  ; next i;
\>>
 
Output:
Outputs for arguments 130, 607 and 2281, respectively:

{ 2 3 5 7 13 17 19 31 61 89 107 127 } 
{ 2 3 5 7 13 17 19 31 61 89 107 127 521 607 }
{ 2 3 5 7 13 17 19 31 61 89 107 127 521 607 1279 2203 2281 }

These take respectively 1m 22s on the real HP 50g, 4m 29s and 10h 29m 23s on the emulator (Debug4 running on PC under WinXP, Intel(R) Core(TM) Duo CPU T2350 @ 1.86GHz). 

[edit] Ruby

def is_prime ( p )
return true if p == 2
return false if p <= 1 || p.even?
(3 .. Math.sqrt(p)).step(2) do |i|
return false if p % i == 0
end
true
end
 
def is_mersenne_prime ( p )
return true if p == 2
m_p = ( 1 << p ) - 1
s = 4
(p-2).times { s = (s ** 2 - 2) % m_p }
s == 0
end
 
precision = 20000 # maximum requested number of decimal places of 2 ** MP-1 #
long_bits_width = precision / Math.log(2) * Math.log(10)
upb_prime = (long_bits_width - 1).to_i / 2 # no unsigned #
upb_count = 45 # find 45 mprimes if int was given enough bits #
 
puts " Finding Mersenne primes in M[2..%d]:" % upb_prime
 
count = 0
for p in 2..upb_prime
if is_prime(p) && is_mersenne_prime(p)
print "M%d " % p
count += 1
end
break if count >= upb_count
end
puts
Output:
 Finding Mersenne primes in M[2..33218]: 
 M2 M3 M5 M7 M13 M17 M19 M31 M61 M89 M107 M127 M521 M607 M1279 M2203 M2281 M3217 M4253 M4423 M9689 M9941 M11213 M19937 M21701 M23209

[edit] Scala

Library: Scala

In accordance with definition of Mersenne primes it could only be a Mersenne number with prime exponent.

object LLT extends App {
import Stream._
 
def primeSieve(s: Stream[Int]): Stream[Int] =
s.head #:: primeSieve(s.tail filter { _ % s.head != 0 })
val primes = primeSieve(from(2))
 
def mersenne(p: Int): BigInt = (BigInt(2) pow p) - 1
 
def s(mp: BigInt, p: Int): BigInt = { if (p == 1) 4 else ((s(mp, p - 1) pow 2) - 2) % mp }
 
val upbPrime = 9941
println(s"Finding Mersenne primes in M[2..$upbPrime]")
((primes takeWhile (_ <= upbPrime)).par map { p => (p, mersenne(p)) }
map { p => if (p._1 == 2) (p, 0) else (p, s(p._2, p._1 - 1)) } filter { _._2 == 0 })
.foreach { p =>
println(s"prime M${(p._1)._1}: " +
{ if ((p._1)._1 < 200) (p._1)._2 else s"(${(p._1)._2.toString.size} digits)" })
}
println("That's All Folks!")
}
Output:
After approx 20 minutes (2.10 GHz dual core)
Finding Mersenne primes in M[2..9999]
prime M2: 3
prime M3: 7
prime M5: 31
prime M7: 127
prime M13: 8191
prime M17: 131071
prime M19: 524287
prime M31: 2147483647
prime M61: 2305843009213693951
prime M89: 618970019642690137449562111
prime M107: 162259276829213363391578010288127
prime M127: 170141183460469231731687303715884105727
prime M521: (157 digits)
prime M607: (183 digits)
prime M1279: (386 digits)
prime M2203: (664 digits)
prime M2281: (687 digits)
prime M3217: (969 digits)
prime M4253: (1281 digits)
prime M4423: (1332 digits)
prime M9689: (2917 digits)
prime M9941: (2993 digits)
That's All Folks!

[edit] Scheme

;;;The heart of the algorithm
(define (S n)
(let ((m (- (expt 2 n) 1)))
(let loop ((c (- n 2)) (a 4))
(if (zero? c)
a
(loop (- c 1) (remainder (- (* a a) 2) m))))))
 
(define (mersenne-prime? n)
(if (= n 2)
#t
(zero? (S n))))
 
;;;Trivial unoptimized implementation for the base primes
(define (next-prime x)
(if (prime? (+ x 1))
(+ x 1)
(next-prime (+ x 1))))
 
(define (prime? x)
(let loop ((c 2))
(cond ((>= c x) #t)
((zero? (remainder x c)) #f)
(else (loop (+ c 1))))))
 
;;Main loop
(let loop ((i 45) (p 2))
(if (not (zero? i))
(if (mersenne-prime? p)
(begin
(display "M") (display p) (display " ")
(loop (- i 1) (next-prime p)))
(loop i (next-prime p)))))
M2 M3 M5 M7 M13...

[edit] Scilab

  iexpmax=30
n=1
for iexp=2:iexpmax
if iexp==2 then s=0; else s=4; end
n=(n+1)*2-1
for i=1:iexp-2
s=modulo((s*s-2),n)
end
if s==0 then printf("M%d ",iexp); end
end
Output:
M2 M3 M5 M7 M13 M17 M19

[edit] Seed7

To get maximum speed the program should be compiled with -O2.

$ include "seed7_05.s7i";
include "bigint.s7i";
 
const func boolean: isPrime (in integer: number) is func
result
var boolean: prime is FALSE;
local
var integer: upTo is 0;
var integer: testNum is 3;
begin
if number = 2 then
prime := TRUE;
elsif number rem 2 = 0 or number <= 1 then
prime := FALSE;
else
upTo := sqrt(number);
while number rem testNum <> 0 and testNum <= upTo do
testNum +:= 2;
end while;
prime := testNum > upTo;
end if;
end func;
 
const func boolean: lucasLehmerTest (in integer: p) is func
result
var boolean: prime is TRUE;
local
var bigInteger: m_p is 0_;
var bigInteger: s is 4_;
var integer: i is 0;
begin
if p <> 2 then
m_p := 2_ ** p - 1_;
for i range 2 to pred(p) do
s := (s ** 2 - 2_) rem m_p;
end for;
prime := s = 0_;
end if;
end func;
 
const proc: main is func
local
var integer: p is 2;
begin
writeln(" Mersenne primes:");
while p <= 3217 do
if isPrime(p) and lucasLehmerTest(p) then
write(" M" <& p);
flush(OUT);
end if;
incr(p);
end while;
writeln;
end func;

Original source: lucasLehmerTest, isPrime

Output:
 Mersenne primes:
 M2 M5 M7 M13 M17 M19 M31 M61 M89 M107 M127 M521 M607 M1279 M2203 M2281 M3217

[edit] Tcl

Translation of: Pop11
proc main argv {
set n 0
set t [clock seconds]
show_mersenne 2 [incr n] t
 
for {set p 3} {$p <= [lindex $argv 0]} {incr p 2} {
if {![prime $p]} continue
if {[LucasLehmer $p]} {
show_mersenne $p [incr n] t
}
}
}
proc show_mersenne {p n timevar} {
upvar 1 $timevar time
set now [clock seconds]
puts [format "%2d: %5ds M%s" $n [expr {$now - $time}] $p]
set time $now
}
proc prime i {
if {$i in {2 3}} {return 1}
prime0 $i [expr {int(sqrt($i))}]
}
proc prime0 {i div} {
expr {!($i % $div)? 0: $div <= 2? 1: [prime0 $i [incr div -1]]}
}
proc LucasLehmer p {
set mp [expr {2**$p-1}]
set s 4
for {set i 2} {$i < $p} {incr i} {
set s [expr {($s**2 - 2) % $mp}]
}
expr {$s == 0}
}
 
main 33218
Output:

The program was still running, but as the next Mersenne prime is 19937 there will be a long wait until the program finds it.

 1:     0s  M2
 2:     0s  M3
 3:     0s  M5
 4:     0s  M7
 5:     0s  M13
 6:     0s  M17
 7:     0s  M19
 8:     0s  M31
 9:     0s  M61
10:     0s  M89
11:     0s  M107
12:     0s  M127
13:     1s  M521
14:     0s  M607
15:     4s  M1279
16:    21s  M2203
17:     4s  M2281
18:    69s  M3217
19:   180s  M4253
20:    39s  M4423
21:  5543s  M9689
22:   655s  M9941
23:  3546s  M11213

[edit] TI-83 BASIC

19→M
1→N
For(E,2,M)
If E=2
Then:0→S
Else:4→S
End
(N+1)*2-1→N
For(I,1,E-2)
Reminder(S*S-2,N)→S
End
If S=0
Then:Disp E
End
End
Output:
2 
3 
5 
7 
13 
17 
19

[edit] VBScript

iexpmax = 15
n=1
out=""
For iexp = 2 To iexpmax
If iexp = 2 Then
s = 0
Else
s = 4
End If
n = (n + 1) * 2 - 1
For i = 1 To iexp - 2
s = (s * s - 2) Mod n
Next
If s = 0 Then
out=out & "M" & iexp & " "
End If
Next
Wscript.echo out
Output:
M2 M3 M5 M7 M13 

[edit] Visual Basic .NET

Works with: Visual Basic .NET version 2011
Public Class LucasLehmer
Private Sub btnGo_Click(sender As Object, e As EventArgs) Handles btnGo.Click
Const iexpmax = 31
Dim s, n As Long
Dim i, iexp As Integer
n = 1
txtOut.Text = ""
For iexp = 2 To iexpmax
If iexp = 2 Then
s = 0
Else
s = 4
End If
n = (n + 1) * 2 - 1
For i = 1 To iexp - 2
s = (s * s - 2) Mod n
Next i
If s = 0 Then
txtOut.Text = txtOut.Text & "M" & iexp & " "
End If
Next iexp
End Sub
End Class
Output:
M2 M3 M5 M7 M13 M17 M19 M31 

[edit] zkl

Using Extensible prime generator#zkl and the GMP library.

var BN=Import("zklBigNum");	// lib GMP
primes:=Utils.Generator(Import("sieve").postponed_sieve);
fcn isMersennePrime(p){
if(p==2) return(True);
mp:=BN(1).shiftLeft(p) - 1; // 2^p - 1, a BIG number, like 1000s of digits
s:=BN(4); do(p-2){ s.mul(s).sub(2).mod(mp) } // the % REALLY cuts down on mem usage
return(s==0);
}

Calculating S(n) is done in place (overwriting the value in the BigInt with the result); this really cuts down on memory usage.

mersennePrimes:=primes.tweak(fcn(p){ isMersennePrime(p) and p or Void.Skip });
println("Mersenne primes:");
foreach mp in (mersennePrimes) { print(" M",mp); }

This will "continuously" spew out Mersenne Primes.

Tweaking a Walker (aka iterator, Generators are a class of Walker) basically puts a filter on the underlying iterator, in this case, ignoring prime numbers that are not Mersenne primes and passing those that are.

Output:
Mersenne primes:
 M2 M3 M5 M7 M13 M17 M19 M31 M61 M89 M107 M127 M521 M607 M1279 M2203
 M2281 M3217 M4253 M4423 M9689 M9941 M11213 M19937 M21701 M23209 M44497 ^C

Additionally, this problem is readily threaded and has a linear speedup. Since there are lots of calculations between results, the [bigger] results are basically time sorted. However, N times faster doesn't mean much given the huge calculations used by the LL test (math with thousands of digits ain't quick).

Using five threads:

ps:=Thread.Pipe(); mpOut:=Thread.Pipe(); // how the threads will communicate
fcn(ps){ // a thread to generate primes, sleeps most of the time
Utils.Generator(Import("sieve").postponed_sieve).pump(ps)
}.launch(ps);
 
do(4){ // four threads to perform the Lucas-Lehmer test
fcn(ps,out){ ps.filter2s(out,isMersennePrime) }.launch(ps,mpOut)
}
println("Mersenne primes:");
foreach mp in (mpOut) { print(" M",mp); }
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