http://www.perlmonks.org?node_id=1197296

in reply to High Performance Game of Life

Unfortunately, method calling in Perl is expensive. The following change to Organism.pm will run two times faster simply by inlining is_alive.

Before:

```sub is_alive {
my \$self = shift;
return 0 + exists \$self->{Cells}->{ join ':', @_ };
}

# Return the list of dead cells surrounding a cell
my ( \$self, \$x, \$y ) = @_;
( (join ':', \$x - 1, \$y - 1) x !\$self->is_alive(\$x - 1, \$y - 1),
(join ':', \$x - 1, \$y    ) x !\$self->is_alive(\$x - 1, \$y    ),
(join ':', \$x - 1, \$y + 1) x !\$self->is_alive(\$x - 1, \$y + 1),
(join ':', \$x    , \$y - 1) x !\$self->is_alive(\$x    , \$y - 1),
(join ':', \$x    , \$y + 1) x !\$self->is_alive(\$x    , \$y + 1),
(join ':', \$x + 1, \$y - 1) x !\$self->is_alive(\$x + 1, \$y - 1),
(join ':', \$x + 1, \$y    ) x !\$self->is_alive(\$x + 1, \$y    ),
(join ':', \$x + 1, \$y + 1) x !\$self->is_alive(\$x + 1, \$y + 1) );
}

sub get_num_live {
my ( \$self, \$x, \$y ) = @_;
\$self->is_alive( \$x - 1, \$y - 1 )
+ \$self->is_alive( \$x - 1, \$y     )
+ \$self->is_alive( \$x - 1, \$y + 1 )
+ \$self->is_alive( \$x    , \$y - 1 )
+ \$self->is_alive( \$x    , \$y + 1 )
+ \$self->is_alive( \$x + 1, \$y - 1 )
+ \$self->is_alive( \$x + 1, \$y     )
+ \$self->is_alive( \$x + 1, \$y + 1 );
}

After:

```# Return the list of dead cells surrounding a cell
my ( \$cells, \$x0, \$y0 ) = ( shift->{Cells}, @_ );
my ( \$x1, \$x2, \$y1, \$y2 ) = ( \$x0 - 1, \$x0 + 1, \$y0 - 1, \$y0 + 1 );
( ( "\$x1:\$y1" ) x !( 0 + exists \$cells->{ "\$x1:\$y1" } ),
( "\$x1:\$y0" ) x !( 0 + exists \$cells->{ "\$x1:\$y0" } ),
( "\$x1:\$y2" ) x !( 0 + exists \$cells->{ "\$x1:\$y2" } ),
( "\$x0:\$y1" ) x !( 0 + exists \$cells->{ "\$x0:\$y1" } ),
( "\$x0:\$y2" ) x !( 0 + exists \$cells->{ "\$x0:\$y2" } ),
( "\$x2:\$y1" ) x !( 0 + exists \$cells->{ "\$x2:\$y1" } ),
( "\$x2:\$y0" ) x !( 0 + exists \$cells->{ "\$x2:\$y0" } ),
( "\$x2:\$y2" ) x !( 0 + exists \$cells->{ "\$x2:\$y2" } ) );
}

sub get_num_live {
my ( \$cells, \$x0, \$y0 ) = ( shift->{Cells}, @_ );
my ( \$x1, \$x2, \$y1, \$y2 ) = ( \$x0 - 1, \$x0 + 1, \$y0 - 1, \$y0 + 1 );
( 0 + exists \$cells->{ "\$x1:\$y1" } )
+ ( 0 + exists \$cells->{ "\$x1:\$y0" } )
+ ( 0 + exists \$cells->{ "\$x1:\$y2" } )
+ ( 0 + exists \$cells->{ "\$x0:\$y1" } )
+ ( 0 + exists \$cells->{ "\$x0:\$y2" } )
+ ( 0 + exists \$cells->{ "\$x2:\$y1" } )
+ ( 0 + exists \$cells->{ "\$x2:\$y0" } )
+ ( 0 + exists \$cells->{ "\$x2:\$y2" } );
}