Arasan 19.0 + updated test suite

[jdart]

Arasan 19 is available from http://www.arasanchess.org.

Changes in Arasan 19.0:
1) Adjust scoring for some pawnless endgames.
2) Add Syzygy tablebase support, using Fathom library.
3) Convert codebase to C++ 11. Remove support for older compilers.
Use standard types from stdint. Use platform bswap macros where
available for byte re-ordering. Misc other code cleanups and
portability fixes.
4) Update killers on lower bound hash hit. But not if in check. Move
guard conditions for killer/history update to search.cpp and make
them consistent.
5) Change qsearch pruning conditions.
6) Limit threat move extension to low depth as Stockfish did.
7) Fixes to IID. Change IID depth conditions.
8) Omit all forms of forward pruning (before the move gen/
search loop) when any of IID, VERIFY or SINGULAR flags are set.
9) Allow fractional (half-depth) reductions. Limit reductions so they
don't hit the q-search. Don't set LMR flag if reduction is 0. Change
min LMR search depth to 3 ply.
10) Use only 2 killer moves (not also killers from previous ply as
formerly).
11) Do pruning after LMR and using reduced depth (except use non-reduced
depth for LMP).
12) Modify how history scores are maintained and used (similar to Texel).
13) Make history & refutation tables local to threads.

I estimate about +20 ELO over 18.3. Could be more or less.

The Mac compile now uses clang and should be faster than the ones I have made before, which used GCC 4.2.

There is also an updated version of the Arasan test suite (see http://arasanchess.org/testsuite.shtml). This has some new positions and is harder than the previous version overall. I have verified the solutions as best I can.

--Jon

[Paloma]

Hi Jon, thanks for both

[velmarin]

I tested whether the program shows that uses a tablebase syzygy. Unfortunately, nowhere does not show program that uses syzygy.

Yes, in Arena and Fritz GUIs works well and shows TBhits perfectly.

Good job, John.

[jdart]

I am not sure what you expect to see.

For example, if you start Arasan and give the "uci" command you should see this:

Code: Select all

uci
id name Arasan 19.0
id author Jon Dart
option name Hash type spin default 64 min 4 max 64000
option name Ponder type check default true
option name Use tablebases type check default true
option name Tablebases type combo var Syzygy var Nalimov var Gaviota default Syzygy
option name GaviotaTbPath type string default gtb
option name GaviotaTbCache type spin default 8 min 1 max 32
option name NalimovPath type string default TB
option name NalimovCache type spin default 8 min 1 max 32
option name SyzygyPath type string default c:\chess\syzygy
option name SyzygyUse50MoveRule type check default true
option name SyzygyProbeDepth type spin default 4 min 0 max 64
option name MultiPV type spin default 1 min 1 max 10
option name OwnBook type check default true
option name Book selectivity type spin default 50 min 0 max 100
option name Threads type spin default 1 min 1 max 64
option name UCI_LimitStrength type check default false
option name UCI_Elo type spin default 2600 min 1000 max 2600
uciok

and so you can see there are Syzygy options. Same with Winboard: it supports the standard "egt" feature.

If you want tablebase support in the native Arasan GUI, there is not UI support for that at present but you can edit the arasan.rc file that is in the install directory and configure it to use tablebases.

--Jon

[velmarin]

Very interesting how works with Syzygy Arasan.

[jdart]

/home/jdart/chess/syzygy is the default in the arasan.rc file. But if there are no tablebases there it should not initialize.

Still it does look like there might be a problem with the Windows binaries, for the use case where the tb info is configured using the .rc file and is not set through UCI or Winboard options. I am testing a fix.

--Jon

[jdart]

Actually it looks ok (I had a typo in the file I was using for testing). It is initializing ok.

--Jon

[Graham Banks]

Put all of your Syzygy files in one folder, perhaps D:\Syzygy and try again with just that path.
Having two paths where it only wants one is probably meaning it doesn't use either.

[Graham Banks]

Thanks for the advice. Unfortunately, the program also does not want to show tablebase. I tried another programie- Shredder Classic 4 - I do not want to show.

Pretty sure I saw Arasan using them under ChessGUI. Will keep an eye out and take a screenshot if I can.

[jdart]

Ok, there does seem to be a problem.

Arena at least seems to always send the UCI NalimovPath option before sending the Syzygy path. And that may confuse the engine.

In Winboard mode under Arena I do see the tablebases being initialized but they do not seem to be used.

I am investigating.

--Jon