Re: [Bug-gnubg] Gnubg's Cache and Plies > 3 - problem?

[Jonathan Kinsey]

I've checked this in.

Jon

Jonathan Kinsey wrote:
> 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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