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# Stockfish 9

Stockfish 9 released.

http://abrok.eu/stockfish/
also:

https://github.com/official-stockfis...bb8f930472fc43
Compiled by Alexei Chernakoff

Cfish 9 for Android
https://app.box.com/s/x527xsz3hhuzqewygxuuvllboasshfll

Stockfish 9 for Android
https://app.box.com/s/g2z3d7xumpagvhgebi7tppn0qs62ye5j

Brainfish 010218 for Android
https://app.box.com/s/9i2qz5dk63keg9rj66cftkbhwhb47x9s
Stockfish 9 for Android by Alexei Chernakoff
https://app.box.com/s/bnbt7quvq7zrxkum6qo46f99ggnrtokz
**This version is the same as Stockfish_9 arm7 but PGO optimized, thus calculates slightly faster
At last, Stockfish has Dynamic Contempt!
Source: http://abrok.eu/stockfish/

Author: Stefano Cardanobile
Date: Fri Feb 9 19:07:19 2018 +0100
Timestamp: 1518199639

Introduce dynamic contempt

Make contempt dependent on the current score of the root position.

The idea is that we now use a linear formula like the following to decide
on the contempt to use during a search :

contempt = x + y * eval

where x is the base contempt set by the user in the "Contempt" UCI option,
and y * eval is the dynamic part which adapts itself to the estimation of
the evaluation of the root position returned by the search. In this patch,
we use x = 18 centipawns by default, and the y * eval correction can go
from -20 centipawns if the root eval is less than -2.0 pawns, up to +20
centipawns when the root eval is more than 2.0 pawns.

To summarize, the new contempt goes from -0.02 to 0.38 pawns, depending if
Stockfish is losing or winning, with an average value of 0.18 pawns by default.

STC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 110052 W: 24614 L: 23938 D: 61500
http://tests.stockfishchess.org/tests/view/5a72e6020ebc590f2c86ea20

LTC:
LLR: 2.97 (-2.94,2.94) [0.00,5.00]
Total: 16470 W: 2896 L: 2705 D: 10869
http://tests.stockfishchess.org/tests/view/5a76c5b90ebc5902971a9830

A second match at LTC was organised against the current master:

ELO: 1.45 +-2.9 (95%) LOS: 84.0%
Total: 19369 W: 3350 L: 3269 D: 12750
http://tests.stockfishchess.org/tests/view/5a7acf980ebc5902971a9a2e

Finally, we checked that there is no apparent problem with multithreading,
despite the fact that some threads might have a slightly different contempt

Match of this version against master, both using 5 threads, time control 30+0.3:
ELO: 2.18 +-3.2 (95%) LOS: 90.8%
Total: 14840 W: 2502 L: 2409 D: 9929
http://tests.stockfishchess.org/tests/view/5a7bf3e80ebc5902971a9aa2

Include suggestions from Marco Costalba, Aram Tumanian, Ronald de Man, etc.

Bench: 5207156
Cfish_150218.pgo
by Alexei Chernakoff
New patch: Updated to "Simplify trapped rook"
https://app.box.com/s/s8r3erqhdg8m1y166hkypx5808gfg6ty
Stockfish_240218 (pgo popcnt arm7, arm64v8) Android
Author: DU-jdto

Updated with the following patch:
Date: Sat Feb 24 13:12:04 2018 +0100
Timestamp: 1519474324

Simplification: do razoring only for depth 1

The razoring heuristic is quite a drastic pruning technique,
using a depth 0 search at internal nodes of the search tree
to estimate the true value of depth n nodes. This patch limits
this razoring to the case of internal nodes of depth 1.
Author: Jarrod Torriero (DU-jdto)

STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 8043 W: 1865 L: 1716 D: 4462
http://tests.stockfishchess.org/tests/view/5a90a9290ebc590297cc86c1

LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 32890 W: 5577 L: 5476 D: 21837
http://tests.stockfishchess.org/tests/view/5a90c8510ebc590297cc86d5

Opportunities opened by this patch: it would be interesting to
know if it brings Elo to re-introduce razoring or soft razoring
at depth >= 2, maybe using a larger margin to compensate for the
increased pruning effect.

Bench: 5227124
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