On 2007-01-04, at 09:47 , Darse Billings wrote:

>
> On 4-Jan-07, at 9:23 AM, Darse Billings wrote:
> >
> > I'm thinking it might be advantageous to represent cards keeping the
> > rank and suit separated (4+2 bits), rather than having to unravel
> the
> > 6-bit representation for integers 0-51. Now the unordered rank
> pattern
> > can be determined quickly with bit operations, (28 bits = 268
> million
> > table entries), and the suit pattern determines the flush
> exceptions.
> >
>
> Specifically:
>
> 2c 001000 2d 001001 2h 001010 2s 001011
> 3c 001100 3d 001101 3h 001110 3s 001111
> 4c 010000 4d 010001 4h 010010 4s 010011
> 5c 010100 5d 010101 5h 010110 5s 010111
> 6c 011000 6d 011001 6h 011010 6s 011011
> 7c 011100 7d 011101 7h 011110 7s 011111
> 8c 100000 8d 100001 8h 100010 8s 100011
> 9c 100100 9d 100101 9h 100110 9s 100111
> Tc 101000 Td 101001 Th 101010 Ts 101011
> Jc 101100 Jd 101101 Jh 101110 Js 101111
> Qc 110000 Qd 110001 Qh 110010 Qs 110011
> Kc 110100 Kd 110101 Kh 110110 Ks 110111
> Ac 111000 Ad 111001 Ah 111010 As 111011
>
> Note that an unordered set of 5 cards can be held in a single 32-bit
> integer, which can then be converted to a hand value with a table
> look-up, and to a (sorted) canonical representative with another
> (small) table look-up...
If you're going to do a table lookup, is there some significant
advantage from the binary representation over, say,

index = card0+52*(card1 + 52*(card2 ... ))

which results in a smaller table (though not by enough to pack
another card into 32 bits).

Is the binary manipulation faster than multiply/add on current
processors?

Also (directed at everyone), in doing these tests, you should try
some mode of usage other than sequentially iterating through hands,
since that introduces a large degree of locality and may (depending
on the algorithm) reduce the cost of table lookups and/or
unpredictable branches. (This applies to the existing poker-eval
code as well.) For example, a good test would be evaluating randomly
generated hands against each other, with a control test to remove the
cost of generating the hands.