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Re^3: Near equal partitions.

by BrowserUk (Pope)
on Jan 14, 2011 at 07:45 UTC ( #882302=note: print w/replies, xml ) Need Help??


in reply to Re^2: Near equal partitions.
in thread Near equal partitions.

It is probably because I'm using a 64-bit build? For reference, here is my benchmark code:

#! perl -slw use strict; use Benchmark qw[ cmpthese ]; use POSIX qw(ceil); sub buk{ my( $n, $m ) = @_; my @parts = (int( $n / $m )) x $m; $n -= $_ for @parts; my $i =0; $parts[ $i++ ]++ while $n--; return @parts; } sub eli { my ($n, $m) = @_; my $r = $n%$m; # <== my @parts = (($n-$r)/$m) x $m; # <== my $i=0; $parts[$i++]++ while $r--; return @parts; } sub syp { my ($n, $m) = @_; my @parts; for(0 .. $m - 1) { $n -= $parts[$_] = ceil($n / $m); $m -= 1; } return @parts; } sub ike { my ($n, $m) = @_; my $q = int($n / $m); my $r = $n % $m; return ($q+1) x $r, ($q) x ($m-$r); } printf "buk: 97/$_ [%s]\n", join ' ', buk( 97, $_ ) for 2 .. 9; printf "eli: 97/$_ [%s]\n", join ' ', eli( 97, $_ ) for 2 .. 9; printf "syp: 97/$_ [%s]\n", join ' ', syp( 97, $_ ) for 2 .. 9; printf "ike: 97/$_ [%s]\n", join ' ', ike( 97, $_ ) for 2 .. 9; cmpthese -1, { buk => q[ for my $n ( 2 .. 100 ) { for my $m ( 3 .. 50 ) { my @n = buk( $n, $m ); } } ], eli => q[ for my $n ( 2 .. 100 ) { for my $m ( 3 .. 50 ) { my @n = eli( $n, $m ); } } ], syp => q[ for my $n ( 2 .. 100 ) { for my $m ( 3 .. 50 ) { my @n = syp( $n, $m ); } } ], ike => q[ for my $n ( 2 .. 100 ) { for my $m ( 3 .. 50 ) { my @n = ike( $n, $m ); } } ], }

With regard to the integer/float division performance. Regardless of any raw machine-level differences in integer/double division--which these days are far less pronounced than previously--the cost of Perl math is always dominated by the number of Perl opcodes to perform the calculation, not the raw machine code performance.


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