You guys, I wrote a perl program to calculate the 13 million digits of 2**43_112_609-1: 

use bignum only => "GMP";  # GMP added later
use strict;

my $x = 43_112_609; warn "x isa " . ref($x). "!\n";
my $y = ( (2**$x) - 1 );

open my $out, ">", "huge.txt" or die $!;
print $out "huge prime: ", $y, "\n";

[download]

I mean, I know bignum isn't exactly news, but I just think it's a very cool package.

ref: daily galaxy: ultimate-prime.html

-Paul

Replies are listed 'Best First'.
Re: bignum rocks 2^43_112_609-1
by JavaFan (Canon) on Sep 29, 2008 at 14:30 UTC
    Unfortunally, bignum is also kind of slow. Take the following program: 
    use 5.010;
use bignum;
use warnings;
use strict;

my $x = shift || 100;
my $y = 2**$x - 1;

say $y;

    [download]
    calling it with 500000 as argument took 3m02s on my box (output redirected to /dev/null). The equivalent 
    echo '2^500000-1'|bc > /dev/null

    [download]
    only took 4 seconds.

    So, in general, if I want arbitrary precision numbers, I use bc instead of bignum.

[reply]
[d/l]
[select]
      By default, bignum uses a backend module written in pure Perl to do the math, but you can instruct it to use a different implementation, for instance the fast GMP library (see this):

      On my computer: 

      $ time echo '2^500000-1'|bc >/dev/null 
real    0m3.057s
user    0m2.920s
sys     0m0.010s

$ time perl -e 'use bigint only => 'GMP'; my $x = 2 ** 500000 - 1; pri
+nt $x' >/dev/null 
real    0m0.201s
user    0m0.160s
sys     0m0.010s

      [download]
      In that case, the perl version is ~15 times faster!!!
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[d/l]
        See, I'm under the impression that bignum uses Math::BigInt, which uses Math::BigInt::GMP if available. Since I have Math::BigInt::GMP installed, I'd assume (by default) it'd use that. But otherwise, I see what you mean.

        It seems reasonable to me to have bigint require GMP. I wonder if there are cases where you'd really want to do bignum processing in pure Perl.

        UPDATE: this is false. bignum explicitly asks for ::Calc. Why would it do that?

        -Paul

[reply]
      Wow, that's a huge difference. Is this a GMPlib problem or a bignum.pm problem? That's the question in my mind.

      -Paul

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Re: bignum rocks 2^43_112_609-1
by Anonymous Monk on Sep 29, 2008 at 12:18 UTC
    Like pouring liquid nitro on some beans, cool :D
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Re: bignum rocks 2^43_112_609-1
by bart (Canon) on Oct 06, 2008 at 14:44 UTC
    print $out "huge prime: ", $y, "\n";
    Here's to hoping it is a prime.

    update: Well, ambrus claims it must be, pointing towards this.

[reply]
[d/l]
      My original post totally links to an article about 2**43_112_609-1.

      -Paul

[reply]
Re: bignum rocks 2^43_112_609-1
by swampyankee (Parson) on Oct 07, 2008 at 02:17 UTC

    My copy of maxima dies. 8-(

    (

    Information about American English usage here and here. Floating point issues? Please read this before posting. — emc

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