Computer Chess Club Archives




Subject: I need your opinion about this hash entry structure

Author: Federico Corigliano

Date: 18:52:56 01/02/04

My current hash entry uses a struct and needs 40 bits. I calculated that I can
optimize the size using two unsigned 64 bits integers with the following

struct hashEntry {
    uint64  a;
    uint64  b;

Name       Bits    Description                       Access
Hash key   64      Hash key signature                (entry.a)
Depth      10      Position's search depth*          (entry.b >> 54)
Score      16      Position's score (-32767...32767) (entry.b >> 38) & 0xffff
Move       32      Position's best move              (entry.b >> 6) & 0xffffffff
Age        3       Position's age                    (entry.b >> 3) & 0x7
Threat     1       Threat's extension flag           (entry.b >> 2) & 0x1
Type       2       Upper, lower, exact or none       (entry.b & 0x3)
Total:     128 (16 bytes)

* I use a value of 16 for a full ply, so the max search depth is 63, pretty

There is a high possibility of errors, because I don't implemented yet.
I need your opinion about it, and if is needed to optimize it, how to do it.

Thanks in advance

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