Re: [Bug-gnubg] Makebearoff questions and errors

[Joern Thyssen]

On Tue, Dec 03, 2002 at 02:46:24PM -0000, Ian Shaw wrote
> What are the trade-offs with specifying different hash sizes? Is there
> any difference between the terms "size of hash" used for 2-sided, and

The hash size is just given in bytes. 

For one sided bearoff databases each position requires 128 bytes.

For the two sided bearoff database it requires something different
(can't remember).

> "size of cache" used for 1-sided?
> 
> Is there any interaction between the one-sided and two-sided
> databases? Can they look up results in each other to save time?

No. The database specified with the -O option has to be exactly the same
kind.

> _____________________________________________________________________________________
> 
> Is there any demand for pre-generated databases? The 6x8 two-sided one
> took about an hour on my PC, so I'd be happy to do larger ones and
> make them available. Joseph isn't giving us any more rollouts to do,
> so I can give it some CPU time. I could post them on a website, in
> parts or as a whole.

Probably, but I would very much like to wait until the code is
stabilised. I'm pretty confident that the one sided code is working, but
there is still some things to do with the two-sided.

I don't think the values produced are wrong, but the performance stinks
for larger databases.

> Total number of positions    :   1502337600
> Size of resulting file       :   -866201088 bytes
> 6x15:
> Total number of positions    :  -1350385600
> Size of resulting file       :   2081817088 bytes
> 
> Perhaps there's a problem converting between signed & unsigned integers?

Hmm, some kind of overflow. I'll look at it.

> _____________________________________________________________________________________
> 
> Is there a way of storing a small(ish) database in the gnubg
> directory, and having a larger one on CD? GnuBg could use the local
> one where possible and go to the CD if it exists.

No, and it'll most likely not be implemented. First, I think it will be very
slow; and scond, most people have large enough harddisks to spend 1GB on
bearoff databases :-)

> _____________________________________________________________________________________
> 
> I'm having trouble extending my database. I get the message, "Error 
> initialising old bearoff database!
> 
> C:\GnuBg>makebearoff -t 6x4 -O 6_3_gnu_ts.bd -f gnubg_ts.bd

C:\GnuBg>makebearoff -t 6x4 -O 6_3_gnubg_ts.bd -f gnubg_ts.bd ??
                                      ^^

> 
> Creating the one-sided database didn't generate the same error, but
> didn't appear to use the existing one. (See final line):

I fixed a bug yesterday in the bearoff interface: it "forgot" to
increment the number of reads.

Jørn