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Arasan

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Arasan 17.3

Changes in Arasan 17.3 (Sept. 2014):
1) Reduce doubled pawn score in endgame.
2) Fix some bugs involving hash size settings for UCI.
3) Minor changes to outpost scores.
4) Fix a couple bugs in "makebook" program.
5) Some king safety enhancements.
6) Tuning of futility pruning parameters.
7) History pruning disabled.
8) Fixes to history and killer move handling.
9) Simplify capture extension code and disable "easy nove" if
capturing the last piece.
10) Increase see pruning depth to 1.5 ply.

Windows installer 
Linux/Mac source (tarball) 
Source code for Windows 
Windows engine + book only (includes 64-bit versions) 
Linux chess engine binaries + book 
Mac chess engine binary + book

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From the author "Jon Dart" in another Forum:

"Arasan 17.3 is available from http://www.arasanchess.org.

Changes in Arasan 17.3 (Sept. 2014):
1) Reduce doubled pawn score in endgame.
2) Fix some bugs involving hash size settings for UCI.
3) Minor changes to outpost scores.
4) Fix a couple bugs in "makebook" program.
5) Some king safety enhancements.
6) Tuning of futility pruning parameters.
7) History pruning disabled.
8) Fixes to history and killer move handling.
9) Simplify capture extension code and disable "easy nove" if
capturing the last piece.
10) Increase see pruning depth to 1.5 ply.

Plus as usual there are book improvements.

In matches against version 17.2, this version scores only a little better. But it is stronger against other programs.

Here for example is a match result against Crafty 24.0 (Linux, blitz 5+3, 1 core, ponder off):

Rank Name Elo + - games score oppo. draws
1 Arasan 17.3 2431 9 8 1200 59% 2369 38%
2 Crafty 24.0 2369 8 9 1200 41% 2431 38%

Note for Arena users: I have probably mentioned this before, but Arena by default sets "-H 32768" as command-line arguments for Arasan. This sets the hash size way too low (the value used to be in kilobytes but for many versions now it is interpreted as a byte value). If you want to set the hash on the command line you can use something like "-H 500M" to set 500MB hash ("G" for gigabyte is accepted, too), or you can just omit the command line and use standard GUI facilities for setting the hash size. (UCI hash options used not to work for setting large hash values but that bug is fixed in this release).

--Jon"

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Arasan 17.4

Changes in Arasan 17.4:
1) Deeper LMR (and different reduction formula). After a LMR search
fails high, first re-search with no reduction but zero width bounds,
then only do a full-width, full-depth search.
2) Reduce q-search pruning margin.
3) Bug fix for pondering in Winboard mode. Engine could fail to ponder
again after a successful ponder.
4) Bug fixes to Winboard analysis mode.
5) Bug fix in Board::wouldAttack.
6) Widen somewhat the range of conditions that will prevent
a move from being pruned, based on the null-move threat (if
there is one).
7) Simpify & tune late-move pruning code and remove vestiges of history
pruning.
8) Add .EXPORT_ALL_VARIABLES target to Linux Makefile, to make build
targets work that depend on redefining CC etc.

Windows installer 
Linux/Mac source (tarball) 
Source code for Windows 
Windows engine + book only (includes 64-bit versions) 
Linux chess engine binaries + book 
Mac chess engine binary + book

descriptionArasan - Page 3 EmptyArasan 17.5 available

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Arasan here

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Arasan 18.0
http://www.arasanchess.org.

Changes in Arasan 18.0:
1) Add refutation table, similar to Gull & Rodent. This is global and
refutations are produced in the phase of move generation after killers.
2) Major restructuring to support automated parameter tuning. Internal
scores are now in millipawns (1/1000 pawn).
3) Changes to material balance scoring: in particular, better evaluation
of some "near draw" situations.
4) Detect K vs K+B+wrong color pawns as draw with >1 pawn (on same file).
5) When in UCI analysis mode, output a move even in legal draw situations
(except stalemate).
6) Changes to reduced-strength mode. Instead of randomizing eval, now
at low strength settings the program will select sub-optimal moves
occasionally.
7) Changes to time management when search fails low.
8 ) Changes to king safety scoring and tuning of related parameters.
9) Change conditions for static null pruning and razoring. Adjust
razor margins.
10) LMR changes: reduce only by full ply increments. Adjust LMR
reduction formula.
11) Replace eval-dependent null depth reduction with a strictly depth-
dependent formula.
12) Fix GUI bug: changing strength setting during a game was not working.

This version is measurably stronger than 17.5 in my testing, but not by a large amount.

--Jon

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Arasan 18.1

http://www.arasanchess.org/arasan18.1.exe

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Arasan 18.2

http://www.arasanchess.org/

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Author: Jon Dart

Changes in Arasan 18.3:
1) Bug fix: properly handle "cores" and "memory" options for Winboard.
2) Adjust futility margins and allow futility pruning up to depth 5.
3) Modify pruning condiitions slightly.
4) Bug fix: guard against null move in updateHistoryMove.
5) Bug fix: fix locking for PV update.
6) Properly handle errors opening files in tuner program. Don't allow
validation (-V) when running multi-threaded (does not work). Some
code cleanup in the tuner.
7) Fix UCI tablebase type selection option.
8) Remove some restrictions on LMR.
9) Fix padding in NodeInfo for better alignment.
10) Allow reduction of moves in the killer and refutations phases of
movegen.
11) Bug fix: initialize child node from parent in searchSMP.

This is mostly a bug fix release. It is only marginally stronger than 18.2 (single-core) in my testing (about +8 ELO). However I expect the bug fixes will improve stability and may also increase performance especially when multi-threaded.

http://www.arasanchess.org/

descriptionArasan - Page 3 EmptyArasan 19 (April 2016)

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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.

http://www.arasanchess.org/index.shtml

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Arasan 19.1
http://www.arasanchess.org/

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Arasan 20.0
http://www.arasanchess.org/

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Arasan 20.3
http://www.arasanchess.org/

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Arasan 20.4
https://www.arasanchess.org.

I am putting this out a little sooner than I had planned because it fixes a number of bugs that were in 20.3.

Changes in Arasan 20.4:
1) Fix Linux/Mac Makefile so PGO works with clang.
2) Code cleanup. Replace NULL with nullptr in most places (except some C library calls).
3) Fix serious bug in Syzygy tb code for handling cursed losses.
4) Fix "ecocoder" target in Makefile and fix ecocoder code (sync with changes to Notation).
5) Updates to "pgnselect" utility program.
6) A few fixes in the tuner program. Remove ordinal objective (was not working properly).
7) Add -d option to test command so can do fixed depth. Profile uses fixed depth now.
8) Some updates to the label_positions.py tool.
9) Re-tune parameters with larger traning set and more frequent PV updates.
10) Bug fixes in "easy move" code.
11) Some minor changes/fixes to root move ordering.
12) Bug fixes for UCI multi-pv mode.
13) Add UCI contempt option.

This version is about +16 ELO stronger than 20.3 in my testing, on an arbitrary scale where current versions about ELO 2400. So maybe a bit more on a CEGT or CCRL scale.

--Jon

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Arasan 20.5
https://www.arasanchess.org/downld.shtml

From the author:

Changes in Arasan 20.5:
1) Have tuner output objective value to params file.
2) Bug fix in more() function of RootMoveGenerator.
3) Fixes to Syzygy code: enable locking when multi-threaded.
4) Fix very shallow search when MultiPV greater than the number of legal moves.
5) Fix UCI score output when tb hit at root - now outputs score based on tb score
(worked with multipv but not when multipv == 1).
6) Do not exit search for forced mate if UCI and search type is fixed depth or fixed time.
7) Don't execute move after UCI "bestmove" Wait for GUI to send position.
8) Remove Nalimov and Gaviota tb support.
9) Fix mate score output in GUI.
10) Add code to save/restore window flags and state in GUI.

I expect this version to perform pretty much on a par with Arasan 20.4: all the changes are basically bug fixes, not performance improvements. But some of the fixes are significant: in particular, the tablebase code fixes may prevent occasional crashes when running multithreaded with tablebases in use.

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Arasan 21.0

http://www.arasanchess.org/

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Arasan 21.1

https://www.arasanchess.org/

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Arasan 21.2

https://www.arasanchess.org/

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Arasan 21.3

https://www.arasanchess.org/

descriptionArasan - Page 3 EmptyArasan 21.4

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Arasan 21.4

https://www.arasanchess.org/

Arasan - Page 3 <a href=Arasan - Page 3 Arasan10" />

Nice engine to play regulating the force.

descriptionArasan - Page 3 EmptyRe: Arasan

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Hi,
sorry for being a bit off-topic (with regards to Arasan), just reacting to the strenght regulation you pointed out (indeed a nice & useful feature): I would recommend to give a try to Honey including a great adaptive feature. I tested the X5i version, much convincing!
Regards

descriptionArasan - Page 3 EmptyTHANK YOU-for engine

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THANK YOU .for engine
I tried it. thumb up
TRANSLATOR
In the Gui Fritz you have several regulation options in the weakest plays 6 or 7 moves.
In the guide, Mayula only one, even if he puts him in the weakest strength, he plays at the level of a club player.
His style is almost always the same in all strengths - TACTIC - it looks a lot like fritz 6 the way he plays.

Arasan - Page 3 <a href=Arasan - Page 3 2222210" />

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