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That's interesting, but there are reasons other than performance for wanting fix-width integer semantics.

Try coding this with GMP (or any arbitrary precision math):

```#! perl -slw
use strict;
use Math::Int128 qw[int128 uint128];

my \$ZERO = uint128( 0 );
my \$ONE  = uint128( 1 );
my \$ALLONES = ~ \$ZERO;
my \$MASK1 = \$ALLONES / 3;
my \$MASK2 = \$ALLONES / 15 * 3;
my \$MASK3 = \$ALLONES / 255;

sub bcount {
my \$v = shift;
\$v = \$v - ( ( \$v >> 1 ) & \$MASK1 );
\$v = ( \$v & \$MASK2 ) + ( ( \$v >> 2 ) & \$MASK2 );
\$v = ( \$v + ( \$v >> 4 ) ) &  \$MASK4;
my \$c = ( \$v * ( \$MASK3 ) ) >> 120;
return \$c;
}

my \$bits = uint128( 0 );

## set every 3rd bit
\$bits |= \$ONE << \$_ for map \$_*3+1, 0 .. 42;
print \$bits;

## count the bits (43)
print bcount( \$bits );

## now invert them and count again. (85)
print bcount( ~\$bits );

__END__
c:\test>m128.pl
194447066811964836264785489961010406546
43
85

Note: I would have supplied a GMPz version, but I couldn't work out how to do it from the docs. There seem to be a million ways to initialise a number; a million ways to divide two numbers etc, But not so much when it comes to doing bitwise math.

Update: Here's my attempt at a GMP version of the above. Note that it doesn't just produce the wrong results, but it does so silently:

```#! perl -slw
use strict;
use Math::GMPz;

my \$ZERO = Math::GMPz->new( 0 );
my \$ONE  = Math::GMPz->new( 1 );
my \$ALLONES = ~ \$ZERO;
my \$MASK1 = \$ALLONES / 3;
my \$MASK2 = \$ALLONES / 15 * 3;
my \$MASK3 = \$ALLONES / 255;

sub bcount {
my \$v = shift;
\$v = \$v - ( ( \$v >> 1 ) & \$MASK1 );
\$v = ( \$v & \$MASK2 ) + ( ( \$v >> 2 ) & \$MASK2 );
\$v = ( \$v + ( \$v >> 4 ) ) &  \$MASK4;
my \$c = ( \$v * ( \$MASK3 ) ) >> 120;
return \$c;
}

my \$bits = Math::GMPz->new( 0 );

## set every 3rd bit
\$bits |= \$ONE << \$_ for map \$_*3+1, 0 .. 42;
print \$bits;

## count the bits (43)
print bcount( \$bits );

## now invert them and count again. (85)
print bcount( ~\$bits );

__END__
c:\test>gmpz-t.pl
194447066811964836264785489961010406546
0
0

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