Re: Challenge: CPU-optimized byte-wise or-equals (for a meter of beer)

Bit ops?

sub using_str_bit_ops_and_s {
   my ($s1, $s2) = @_;
   (my $mask = $s1) =~ s/[^\x00]/\xFF/g;
   return ($s1 & $mask) | ($s2 & ~$mask);
}
[download]

tr should be faster.

sub using_str_bit_ops_and_tr {
   my ($s1, $s2) = @_;
   (my $mask = $s1) =~ tr/\x00/\xFF/c;
   return ($s1 & $mask) | ($s2 & ~$mask);
}
[download]

Benchmarks:

            Rate    split1   substr1   bit_ops map_split
split1    1.25/s        --      -95%     -100%     -100%
substr1   25.5/s     1939%        --      -96%      -99%
bit_ops    642/s    51313%     2421%        --      -71%
map_split 2230/s   178496%     8657%      247%        --
[download]

Corion's solution humbles my ass-kicking solution! I wonder if a higher density of zeros would boost my rating?

Update: Added tr variant.
Update: Added Benchmarks.

Comment on Re: Challenge: CPU-optimized byte-wise or-equals (for a meter of beer) Select or Download Code

Replies are listed 'Best First'.
Re^2: Challenge: CPU-optimized byte-wise or-equals (for a meter of beer) by bart (Canon) on Sep 12, 2007 at 16:17 UTC
Bit ops? `sub using_str_bit_ops_and_s { my ($s1, $s2) = @_; (my $mask = $s1) =~ tr/\x00/\xFF/c; return ($s1 & $mask) \| ($s2 & ~$mask); }` [download] I was thinking in the same direction, except I'd use xor. After all, `((A xor B ) and 0) xor B` is B, and `((A xor B) and true) xor B` is A, for any value of A and B. So: `sub using_str_bit_xor { my ($s1, $s2) = @_; (my $mask = $s1) =~ tr/\x00/\xFF/c; return (($s1 ^ $s2) & $mask ) ^ $s2; }` [download] Benchmarks: (and yes I did use 64k byte strings): `my $x = pack 'C', map int rand(256), 1 .. 641024; my $y = pack 'C', map int rand(256), 1 .. 641024; using_str_bit_ops_and_s($x, $y) eq using_str_bit_xor($x, $y) or die "Results are different??"; use Benchmark 'cmpthese'; cmpthese -3, { using_str_bit_ops_and_s => sub{ my $r = using_str_bit_ops_and_s($x, +$y) }, using_str_bit_xor=> sub{ my $r = using_str_bit_xor($x, $y) }, };` [download] Result: `Rate using_str_bit_ops_and_s using_str_ +bit_xor using_str_bit_ops_and_s 686/s -- + -16% using_str_bit_xor 821/s 20% + --` [download] The speed gain is humble, but real.	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re^2: Challenge: CPU-optimized byte-wise or-equals (for a meter of beer)
by bart (Canon) on Sep 12, 2007 at 16:17 UTC

Bit ops?
sub using_str_bit_ops_and_s { my ($s1, $s2) = @_; (my $mask = $s1) =~ tr/\x00/\xFF/c; return ($s1 & $mask) | ($s2 & ~$mask); }
[download]

((A xor B ) and 0) xor B

((A xor B) and true) xor B

So:

sub using_str_bit_xor {
   my ($s1, $s2) = @_;
   (my $mask = $s1) =~ tr/\x00/\xFF/c;
   return (($s1 ^ $s2) & $mask ) ^ $s2;
}
[download]

Benchmarks: (and yes I did use 64k byte strings):

my $x = pack 'C*', map int rand(256), 1 .. 64*1024;
my $y = pack 'C*', map int rand(256), 1 .. 64*1024;
using_str_bit_ops_and_s($x, $y) eq using_str_bit_xor($x, $y)
  or die "Results are different??";

use Benchmark 'cmpthese';
cmpthese -3, {
  using_str_bit_ops_and_s => sub{ my $r = using_str_bit_ops_and_s($x, 
+$y) },
  using_str_bit_xor=> sub{ my $r = using_str_bit_xor($x, $y) },
};
[download]

                         Rate using_str_bit_ops_and_s       using_str_
+bit_xor
using_str_bit_ops_and_s 686/s                      --                 
+   -16%
using_str_bit_xor       821/s                     20%                 
+     --
[download]

[reply]
[d/l]
[select]