Author: Daniel Shawul
Date: 01:56:23 05/13/04
Go up one level in this thread
On May 13, 2004 at 04:20:02, José Carlos wrote:
>On May 13, 2004 at 03:35:00, Daniel Shawul wrote:
>
>>Hello
>>
>>My search is fail soft(i return the actual score)
>>when i fail high at the root i widen the window by 3 pawns (300).
>>
>> if(score<=r_alpha)
>> {
>> r_beta=r_alpha;
>> r_alpha=score-300; //r_alpha = -MATESCORE;
>> }
>> else if(score>=r_beta)
>> {
>> r_alpha=r_beta;
>> r_beta=score + 300; //r_beta = MATESCORE;
>> }
>>If the search fail's high at 1.75 score but the real score was 10
>>i get a score of 4.75 (1.75 + 3) in the next iteration. Why? my search is fail
>>soft and the score returned should be independent of beta. If i change the 200
>>to 300,score returned is 4.75??
a correction (1.75 + 2) = 3.75
>
> Are you sure you're doing fail soft? I mean, you need some extra logic, like
>starting off with -INFINITE in alpha nodes and increase the best score even in
>fail lows. You also need to make sure of returning true bounds in qsearch. Also,
>if you do some kind of forward prunning depeding on alpha and beta you won't be
>able to return true scores.
i do futility pruning and other purnings but i always return
(score + margin) in all of the cases. Not alpha.
for example in the following test position
rnb2rk1/ppq2p1p/4p1p1/3pP1B1/3P1Q2/2b2N2/P1P2PPP/2RK1B1R w - - 8 14
1& 34 -0.31 0.05 1. Qxf7+?
1 36 -0.10 0.05 1. Bd3
2 138 -0.44 0.09 1. Bb5
2 172 -0.24 0.09 1. Bf6
3 447 0.10 0.14 1. Bf6 Qa5
3 679 0.16 0.16 1. Bh6!
3 781 0.18 0.16 1. Bh6 Rd8
4 1899 0.15 0.20 1. Bh6 Rd8 2. Qf6 Nc6
5 3778 0.47 0.27 1. Bh6 Re8 2. Qf6
6 10330 0.71 0.33 1. Bh6 Rd8 2. Qf6
7 26798 1.06 0.44 1. Bh6!
7 86808 1.48 0.63 1. Bh6 Qe7 2. Bxf8 Qxf8 3. Qf6 Nd7
8 208184 1.20 0.95 1. Bh6 Qe7 2. Bxf8 Qxf8 3. Bd3 Nd7
4. Ng5 Qg7
9 684592 1.40 2.27 1. Bh6 Nd7 2. Ng5 a6 3. f3
10 3253930 1.42 9.00 1. Bh6 Qe7 2. Qe3 Qb4 3. Bxf8 Kxf8
4. Qh6+ Kg8 5. Bd3 f6
10 5270072 1.75 15.05 1. Bf6!
10 11120355 3.75 33.33 1. Bf6! //here score is 1.75+2=3.75
//full window opened
10 32259429 12.82 87.59 1. Bf6 Qxe5 2. Nxe5 Nd7 3. Nxd7 Bd2
4. Kxd2 Bxd7 5. c4
11& 32784106 12.47 89.17 1. Bf6? Qxe5
if i change margin to 3,the result will be something like this
10 11120355 4.75 33.33 1. Bf6!
10 32259429 12.82 87.59 1. Bf6 Qxe5 2. Nxe5 Nd7 3. Nxd7 Bd2
4. Kxd2 Bxd7 5. c4
11& 32784106 12.47 89.17 1. Bf6? Qxe5
I am very very sure i don't return alpha/beta anywhere in my search.
I also tried turning off hashtable ,nullmove,iid etc but no success.
best
daniel
>
> José C.
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