http://www.perlmonks.org?node_id=1197302

in reply to Re^2: High Performance Game of Life
in thread High Performance Game of Life

On my laptop, the following shaves 4 seconds from one-time stringification per key.

```# 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 );
my ( \$k1, \$k2, \$k3, \$k4, \$k5, \$k6, \$k7, \$k8 );

( ( \$k1 = "\$x1:\$y1" ) x !( 0 + exists \$cells->{ \$k1 } ),
( \$k2 = "\$x1:\$y0" ) x !( 0 + exists \$cells->{ \$k2 } ),
( \$k3 = "\$x1:\$y2" ) x !( 0 + exists \$cells->{ \$k3 } ),
( \$k4 = "\$x0:\$y1" ) x !( 0 + exists \$cells->{ \$k4 } ),
( \$k5 = "\$x0:\$y2" ) x !( 0 + exists \$cells->{ \$k5 } ),
( \$k6 = "\$x2:\$y1" ) x !( 0 + exists \$cells->{ \$k6 } ),
( \$k7 = "\$x2:\$y0" ) x !( 0 + exists \$cells->{ \$k7 } ),
( \$k8 = "\$x2:\$y2" ) x !( 0 + exists \$cells->{ \$k8 } ) );
}

To not allocate the key variables each time, another 2 seconds reduction is possible with the state feature.

```use feature 'state';

# 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 );

state ( \$k1, \$k2, \$k3, \$k4, \$k5, \$k6, \$k7, \$k8 );

( ( \$k1 = "\$x1:\$y1" ) x !( 0 + exists \$cells->{ \$k1 } ),
( \$k2 = "\$x1:\$y0" ) x !( 0 + exists \$cells->{ \$k2 } ),
( \$k3 = "\$x1:\$y2" ) x !( 0 + exists \$cells->{ \$k3 } ),
( \$k4 = "\$x0:\$y1" ) x !( 0 + exists \$cells->{ \$k4 } ),
( \$k5 = "\$x0:\$y2" ) x !( 0 + exists \$cells->{ \$k5 } ),
( \$k6 = "\$x2:\$y1" ) x !( 0 + exists \$cells->{ \$k6 } ),
( \$k7 = "\$x2:\$y0" ) x !( 0 + exists \$cells->{ \$k7 } ),
( \$k8 = "\$x2:\$y2" ) x !( 0 + exists \$cells->{ \$k8 } ) );
}