Primes

#!/usr/bin/python

def get_primes(n):
    if n < 2:  return []
    if n == 2: return [2]
    # do only odd numbers starting at 3
    s = range(3, n+1, 2)
    # n**0.5 simpler than math.sqr(n)
    mroot = n ** 0.5
    half = len(s)
    i = 0
    m = 3
    while m <= mroot:
        if s[i]:
            j = (m*m-3)//2  # int div
            s[j] = 0
            while j < half:
                s[j] = 0
                j += m
        i = i+1
        m = 2*i+3
    return [2]+[x for x in s if x]

for t in range(10):
    res = get_primes(10000000)
    print len(res)

#!/usr/bin/perl -w

use strict;
use warnings;

sub get_primes($)
\{
    my ($n) = @_;

    if ($n < 2) { return (); }
    if ($n == 2) { return (2); }
    # do only odd numbers starting at 3
    my @s = ();
    for (my $i = 3; $i < $n + 1; $i += 2) {
        push(@s, $i);
    }
    # n**0.5 simpler than math.sqr(n)
    my $mroot = $n ** 0.5;
    my $half = scalar @s;
    my $i = 0;
    my $m = 3;
    while ($m <= $mroot) {
        if ($s[$i]) {
            my $j = int(($m*$m - 3) / 2);
            $s[$j] = 0;
            while ($j < $half) {
                $s[$j] = 0;
                $j += $m;
            }
        }
        $i = $i + 1;
        $m = 2*$i + 3;
    }
    my @res = (2);
    foreach (@s) {
        push(@res, $_) if ($_);
    }
    return @res;
}

my @res;
for (1..10) {
    @res = get_primes(10000000);
    print scalar @res; print "\n";
}

#!/usr/bin/env gbs3

Sub GetPrimes(N As Integer) As Integer[]

  Dim aRes As New Integer[]
  Dim S As Integer[]
  Dim I, J, M As Integer
  Dim iMRoot, iHalf As Integer

  If N < 2 Then Return aRes

  If N = 2 Then Return [ 2 ]

  S = New Integer[(N - 3 + 1) \ 2]
  For J = 3 To N Step 2
    S[I] = J
    Inc I
  Next

  iMRoot = Sqr(N)
  iHalf = S.Count
  I = 0
  M = 3

  While M <= iMRoot

    If S[I] Then
      J = (M * M - 3) \ 2
      S[J] = 0
      While J < iHalf
	S[J] = 0
	J += M
      Wend
    Endif

    Inc I
    M = 2 * I + 3

  Wend

  aRes.Add(2)
  For Each I In S
    If I Then aRes.Add(I)
  Next

  Return aRes

End

Dim aRes As Integer[]
Dim I As Integer

For I = 1 To 10
  aRes = GetPrimes(10000000)
  Print aRes.Count
Next