Question

As a fun side-project for myself to help in learning yet another PHP MVC framework, I’ve been writing Reversi / Othello as a PHP & Ajax application, mostly straightforward stuff. I decided against using a multidimensional array for a number of reasons and instead have a linear array ( in this case 64 elements long ) and a couple methods to convert from the coordinates to integers.

So I was curious, is there any other, possibly faster algorithms for converting an integer to a coordinate point?

function int2coord($i){     $x = (int)($i/8);     $y = $i - ($x*8);           return array($x, $y); }  //Not a surprise but this is .003 MS slower on average function int2coord_2($i){     $b = base_convert($i, 10, 8);     $x =  (int) ($b != 0 ? $b/8 : 0); // could also be $b < 8 for condition     $y = $b % 10;     return array($x, $y); } 

And for posterity sake, the method I wrote for coord2int

function coord2int($x, $y){    return ($x*8)+$y; } 

Update:
So in the land of the weird, the results were not what I was expecting but using a pre-computed lookup table has predominantly shown to be the fastest, guess trading memory for speed is always a winner?

• There was a table with times here but I cut it due to styling issues with SO.

Answer 1

I don’t have the time to measure this myself right now, but I would suspect that a pre-computed lookup table would beat your solution in speed. The code would look something like this:

class Converter  {     private $_table;      function __construct()      {         $this->_table = array();         for ($i=0; $i<64; $i++) {             $this->_table[$i] = array( (int)($i/8), (int)($i%8) );          }     }      function int2coord( $i )     {         return $this->_table[$i];     } }  $conv = new Converter();  $coord = $conv->int2coord( 42 ); 

Of course, this does add a lot of over-head so in practice you would only bother to pre-compute all coordinates if you conversion code was called very often.