Hello Monks!

I need to work with some rather large exponents (much too big for ordinary Perl scalar), on the order of 2**1024000.

Here's my test program:

#!/usr/bin/env perl

use 5.014;
use Math::BigFloat;
my $POW = 1024000;

my $n = Math::BigFloat->new(2);
say "BigFloat result: " . $n->pow($POW);

[download]

On my system, this takes over 3 minutes to run, and works with perfect precision (i.e., I get a 308255-digit integer). I don't need perfect precision, so I set $n->accuracy(10);, which is plenty for my purposes. However, I still get a huge integer as a result (only this time, it's mostly zeroes), and it still takes over 3 minutes to run.

What I want is a limited-precision floating point number such as 5.194693e308255, that I can compare to other such numbers for sorting, display, and the like. Any more than, say, 10 significant figures, is a waste.

Is there a way (with or without BigFloat) to (quickly) calculate a limited-precision float like 5.195e308255? I feel like I'm missing something obvious.

In reply to Efficiently working with huge exponents by wanna_code_perl

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