RE: [Bug-gnubg] Rollouts - some bugs and suggestions

[Øystein Johansen]

>> 2. When I analyse a match and do a rollout for a double/take
>>    decision, I have to do this BOTH for the doubling decision and for
>>    the take decision. It should only be necessary to do one rollout.
>
>The rollout of a doubling decision gives two lines:
>
>(for a double)
>player n holds 2 cube (where n is the 'takee')
>centred 1 cube
>
>(for a redouble)
>player n holds 4 cube (where n is the 'takee')
>player m holds 2 cube (where m is the redoubler)
>
>So you get both the double/take and nodouble rollouts together

I think Magnar talks about analysing a game. Say you roll out a
double/nodouble decision by one of the players where the player
actually doubled. The move.n union is updated with the analysis
and cubeful equities for holdling the cube and giving the cube.

Now moving to the take decision of the other player, the cubeful numbers in
the analysis is not updated accoring to the rollout. There should be some kind
of way to copy the roullout numbers form the prevoius double/nodouble decision
to the take/drop decision, shouldn't it?

[snip]

>> 4. If I use expert level for checker play and world class 33%
>>    reduction for cube play, next time I open rollout settings cube play
>>    has changed to 25% reduction.
>
>That's a bug. I need someone to explain the code in gtkgame.c:
>
>in EvalWidget, a menu for reduced evaluations is set up with entries
>
>int     text
>0       No reduction
>2       50% speed
>3       33% speed
>4       25% speed
>
>The value 1 is deliberately not put into this menu.
>The menu value is then loaded with
>gtk_option_menu_set_history( the index of the item), but this is off
>by one, since there's no menu item for the value 1.
>The same problem occurs for the Analysis and Evaluation settings.
>
>I'm about to commit a fix

I think you're fix is just ok!

>> 5. It seems to me that not much time is saved by using using a high
>>    level of play for the first few plies and expert for the remainder
>>    as compared to using a high level for all the moves. For example, if
>>    I choose world class for the first five plies and expert for the
>>    rest of the game, I would expect this to be MUCH faster than world
>>    class for all the moves.  This does not seem to be the case. Maybe I
>>    am missing something.
>
>I had the same expectation. When I first put the code in for reduced
>evaluations at later plies, I expected the same. The improvement in
>performance was a lot less than I would have thought. My guess is that
>cacheing is working very well, so that a deeper evaluation will
>already have cached values for the upcoming positions (so the deeper
>evaluation means evaluating the first move takes longer than the
>second, but the second move has all the first rolls already cached). I
>think that the actual number of evaluations done is much closer than I
>would have thought.

Also remember that some games may be truncated by a double/drop before (or
right after) the lower ply starts working. The difference will therefore not
be as high as you might expect.

-Øystein