Re: [computer-go] Modern brute force search in go

[Gian-Carlo Pascutto <gcp@xxxxxxxxx>]

Mark Boon wrote:

> I don't understand this. How does the branching factor get to 10 in go? Are
> you referring to another terminology of branch-factor?
Effective branching factor.

With just a PVS alphabeta search, R=3 nullmove, fairly simple 
evaluation, and no other move ordering besides hashtables, I get:

19x19

 d:  1 s:     3 n:        365 t:     0.4s pv: s18
 d:  2 s:     1 n:       1812 t:     0.5s pv: s18 s19
 d:  3 s:     4 n:       8743 t:     0.7s pv: r18 s18 o18
 d:  4 s:     0 n:     249878 t:     6.6s pv: s18 s3 s7 b18
 d:  5 s:     4 n:     638195 t:    18.0s pv: s18 r18 s3 q3 s15
 d:  6 s:     0 n:   13871970 t:   377.2s pv: s18 r18 s15 t15 b18 o18
 d:  7 s:     4 n:   57710143 t:  2039.0s pv: s18 r18 s15 t15 s3 s7 b18

Or an effective branching factor of 7 to 10.

9x9

 d:  1 s:     3 n:         85 t:     0.7s pv: h8
 d:  2 s:     1 n:        412 t:     0.7s pv: h8 h9
 d:  3 s:     4 n:       1993 t:     0.7s pv: g8 h8 d8
 d:  4 s:     0 n:      25846 t:     1.0s pv: h8 f9 h5 b8
 d:  5 s:     4 n:      69288 t:     1.8s pv: h8 g8 g2 h5 b8
 d:  6 s:     0 n:     641869 t:    15.9s pv: h8 g8 b8 b7 b2 b4
 d:  7 s:     5 n:    3558016 t:    83.0s pv: g2 h5 h8 b8 e8 g9 b2
 d:  8 s:     0 n:   25101795 t:   480.9s pv: h2 g2 b8 c8 h8 h7 b2

Or an effective branching factor of 5 to 7.

--
GCP
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