Looks like are emails crossed quite nicely, anyway I will remove the reduction
code and the noise from the cache and change the plies to 4 bits unless someone
shouts (before tonight I expect).

Jon

Øystein Johansen wrote:
> 
> 
> On Tue, Sep 1, 2009 at 10:16 AM, Michael Petch  > wrote:
> 
> 
>     I began reviewing cache.c and have a major concern that 4 ply
>     exceeds our
>     ability to represent a cache key uniquely. I am thinking out loud
>     here, so
>     anyone can correct me. Eval.c has this:
> 
>      /*
>        * Bit 00-01: nPlies
>        * Bit 02   : fCubeful
>        * Bit 03-10: rNoise
>        * Bit 11   : fMove
>        * Bit 12   : fUsePrune
>        * Bit 13-17: anScore[ 0 ]
>        * Bit 18-22: anScore[ 1 ]
>        * Bit 23-26: log2(nCube)
>        * Bit 27-28: fCubeOwner
>        * Bit 29   : fCrawford
>        */
> 
>       iKey = (
>                ( nPlies ) |
>                ( pec->fCubeful << 2 ) |
>                ( ( ( (int) ( pec->rNoise * 1000 ) ) & 0x00FF ) << 3 ) |
>                ( pci->fMove << 11 ) );
> 
>     Clearly nPlies is forced to the 2 low bits.
> 
> 
> Whoops, this is bad!
> 
> However, why the heck do we have 8 bits for storing the noise? Can't we
> rather have a key that is, say 5 bit for the plies and no bits what so
> ever for noise.
> 
> Then for evaluations with noise we should not cache anything at all, in
> my opinion. Retrieving cached values when using noise seems to me like
> something of more academic interest and studies.
> 
> My suggested solution becomes:
> if ( pec->rNoise ) Do not add eval to cache.
> if ( pec->rNoise ) Do not lookup cache for eval.
> 
> Doesn't that solve it?
> 
> -Øystein
> 
> 
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