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### Re^5: Project Euler (a series of challenging mathematical/computer programming problems)

by GrandFather (Sage)
 on Feb 05, 2006 at 00:29 UTC ( #528026=note: print w/ replies, xml ) Need Help??

I had a go myself to see what was possible with simple code. It doesn't scale well, but is acceptable for the first 100,000 primes.

DWIM is Perl's answer to Gödel
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Re^6: Project Euler (a series of challenging mathematical/computer programming problems)
by BrowserUk (Pope) on Feb 05, 2006 at 00:39 UTC

I just saw that and decided to time the mechanism I suggested. At 1/3rd of a second for the first million, it even surprised me :)

#! perl -slw use strict; use Devel::Timer; my \$T = new Devel::Timer; sub firstNprimes { my \$n = shift; open my \$primes, '<:raw', 'primes.all' or die \$!; my @primes = split ' ', do{ local \$/ = \( \$n * 10 ); <\$primes> }; close \$primes; return \@primes; } \$T->mark( '201' ); my \$ref1 = firstNprimes( 201 ); \$T->mark( '100,000' ); my \$ref2 = firstNprimes( 100_000 ); \$T->mark( '1,000,000' ); my \$ref3 = firstNprimes( 1_000_000 ); \$T->report; __END__ C:\Perl\test\data>..\junk4 Devel::Timer Report -- Total time: 0.3176 secs Interval Time Percent ---------------------------------------------- 02 -> 03 0.3169 99.78% 100,000 -> 1,000,000 01 -> 02 0.0007 0.21% 201 -> 100,000 00 -> 01 0.0000 0.01% INIT -> 201

That's the ascii version, and it does slow down quite quickly due memory allocation as you go larger; 2 million takes 8 seconds.

I might try the binary file version later.

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