Arasan
by Jon Dart

Arasan is a chess program for Windows, Linux and Mac OS.
The Arasan chess engine is licensed under the MIT License..
http://www.arasanchess.org/

Arasan 13.3 is available
I will make some tests to see if there is any improvments in the playstrength or not soon.

Engine Score Ar Ar S-B
1: Arasan13.3 10.0/15 ··············· 11101==1110=01= 50.00
2: Arasan13.2 5.0/15 00010==0001=10= ··············· 50.00

15 games played / Tournament is finished
Name of the tournament: Aras
Site/ Country: LENOVO-BE604D20, United States
Level: Tournament Game in 5 Minutes
Hardware: Celeron(R) Dual-Core CPU T3100 @ 1.90GHz 1895 MHz with 1.0 GB Memory
Operating system: Microsoft Windows XP Professional Service Pack 3 (Build 2600) 32 bit
PGN-File: C:\Program Files\Arena\Tournaments\Aras.pgn
Website:
E-Mail Address:

the strange thing is that 13.2 KN/s speed is always higher than 13.3 , but 13.3 is stronger in playing strength

Arasan 14.0 released

Changes in Arasan 14.0:
1) Board::wouldCheck function handles promotions.
2) Much simplifed time management, functions better in particular under very
short time controls.
3) LMR is performed at root node (formerly was not).
4) Null move uses R=3 with verification.
5) Simplified hash table implementation.
6) Move generator defers SEE test on captures until the move is used (this
was done previously in the qsearch but not elsewhere).
7) Better sort algorithm in move generator.
8) Fixes to learning code. Hash table (w/ learn info) was being cleared
at each new game, now learn info is retained.
10) Some code cleanup, esp. conversion from char * to C++ string usage.
11) Arasan uses Gaviota tablebases. Fix tb probing when en passant
capture possible. Tablebase hits now are cached in the hash table.
12) Additional UCI & winboard options supported. GUI now uses the standard
winboard options command to send options to the engine.
13) Fix bug involving mate scores in UCI analysis mode.
14) Makebook program can directly consume PGN.
15) Arasan engine source is released under the MIT license (same license used by the Gaviota tablebase code).

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

What is the expected elo gain over the previous version?

Arasan 14.0.1 (with UCI promotion fix)
http://www.arasanchess.org/downld.shtml

Arasan 14.0.1 Android JA
http://dl.dropbox.com/u/5047625/arasan-141-android-ja.zip

Arasan 14.1 is available from http://www.arasanchess.org.

Changes in Arasan 4.1:
1) Fix (again) UCI promotion move formatting bug.
2) Fix Winboard "memory" command.
3) Support added for MingW environment (use Linux Makefile for this)
4) Q-search selectively generates only moves that will likely reach
futility threshold.
5) Fix icc Makefile (on Windows).
6) Fix bug in PV display in Windows GUI.

THE DANCE (Final Standings) - Arasan 14.1 64-bit
https://www.chess2u.com/t5914-the-dance#34564

Arasan 14.2 released
http://www.arasanchess.org./downld.shtml

Changes in Arasan 14.2:
1) The chess engine handled input from the the UI in several places
and had duplicate code for scanning input and breaking it into lines.
This is now centralized and simplifed.
2) Some other code cleanup, especially conversion from C-style string
handling to C++.
3) Simplified code for lazy eval. Partial (lazy) scores are no longer
cached in the scoring module (such scores were seldom used anyway).
4) Outpost scores reduced.
5) Tweaked threshold values for history pruning and late move pruning (due
to a bug, 14.1 actually did only late move pruning above depth =
1 ply).
6) Reduced thresholds for static null pruning.
7) Some changes to LMR and root move reduction logic.
8) Bug fix: ensure final stage of ply 0 search window widening sets a
correct upper/lower bound.
9) Improvement to logic for searching checks in q-search.
10) Fix material eval adjustment for Q vs 2R.
11) Support is added for varying the engine strength via UCI or Winboard
options (Arasan GUI supports this too).
12) GUI bug fix: search could hang when a "Go" command is issued when it
is the user's turn to move, and the user then makes a manual move before
the search completes.
13) Winboard driver fixes: pings could be processed out of order in some
cases. Also, an extra move could be sent after Winboard has sent a
"resign" or "result" command.

Arasan 14.2a released
http://www.arasanchess.org/downld.shtml

This is a bug-fix release to 14.2.

Jon Dart wrote:
" I have re-spun the 14.2 release to correct two issues:

1) Hang behavior with native Arasan GUI.

2) Strength reduction not being operational during pondering.

See http://www.arasanchess.org for downloads.

There should be no strength differences or performance changes compared to the original 14.2 release (if strength reduction is not on). "

Arasan 14.2b

Jon Dart wrote:I have re-built the Arasan native GUI to fix a problem that shows up only under Windows 7 (sporadic hang behavior in the GUI).

The updated installer is available at:

http://www.arasanchess.org/arasan14.2b.exe.

The Windows source code archive is also updated with the fix.

I have not changed the Arasan chess engine at all, so if you are using only the engine by itself (with a GUI such as Winboard, Arena, Fritz or Shredder), or if you are not on the Windows platform, there is no need to update.

Arasan 14.3

Changes in Arasan 14.3:
1) King safety is scaled by the opponent's material value (fixing a bug).
2) Adjustments and fixes to strength reduction feature.
3) Fix to material scoring for R vs 2 minors.
4) Do not terminate search after forced move if in analysis mode.

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

Code:

Games Completed = 1000 of 1000 (Avg game length = 14.149 sec)
Settings = RR/32MB/2000ms+100ms/M 700000cp for 7 moves, D 150 moves/EPD:E:\LittleBlitzer\openings.epd(4000)
Time = 4109 sec elapsed, 0 sec remaining

 1.  Arasan 14.2a               522.0/1000   420-376-204     (L: m=232 t=144 i=0 a=0)   (D: r=172 i=32 f=0 s=0 a=0)   (tpm=126.9 d=10.84 nps=0)
 2.  Arasan 14.3                 478.0/1000   376-420-204     (L: m=240 t=180 i=0 a=0)   (D: r=172 i=32 f=0 s=0 a=0)   (tpm=127.1 d=10.85 nps=0)


From Jon Dart- Arasan 15.0 is available from http://www.arasanchess.org/

Changes in Arasan 15.0:
1) Increase static null pruning threshold at low depths.
2) Scoring fixes/improvements: king cover, potential passed pawns,
bad bishop.
3) Fix code that tracks node count per ply 0 move, for move ordering.
4) Changes to LMR reduction amounts and ply 0 reduction threshold.
5) Avoid null move if hash table info indicates it would fail to
generate cutoff.
6) Losing checks are no longer extended, in any case. Threat extension
is now done differently, similar to Stockfish.
7) Re-work of SMP code to increase thread usage by supporting the
"helpful master" algorithm.
8) Fix a bug in communicating with the Fritz interface, specifically
the "process testsuite" command.
9) Fix UCI and console score output so upperbound & lowerbound status
displayed when appropriate.
10) Fix setting Strength option from native GUI.
11) Some GNU Makefile fixes for MingW support. clang is also supported
now.

This version is clearly stronger than 14.3 in my testing. About 25 ELO points on my arbitrary rating scale. Maybe more for CEGT etc where the ratings tend to be higher.

Code:

Games Completed = 1000 of 1000 (Avg game length = 14.361 sec)
Settings = RR/32MB/2000ms+100ms/M 700000cp for 7 moves, D 150 moves/EPD:E:\LittleBlitzer\openings.epd(4000)
Time = 4171 sec elapsed, 0 sec remaining

 1.  Arasan 15.0                 529.5/1000   443-384-173     (L: m=187 t=197 i=0 a=0)   (D: r=140 i=32 f=0 s=1 a=0)   (tpm=127.0 d=11.44 nps=0)
 2.  Arasan 14.3                 470.5/1000   384-443-173     (L: m=252 t=191 i=0 a=0)   (D: r=140 i=32 f=0 s=1 a=0)   (tpm=127.2 d=11.00 nps=0)

Code:

CEGT blitz-rating lists Oct. 03rd 2012

Arasan 15.0 x64 1CPU: 2533 - 1300 (+47 to version 14.2)

http://www.husvankempen.de/nunn/40_4_Ratinglist/40_4_AllVersion/rangliste.html

Arasan 15.1

This is the same version that played in the recent ACCA online tournament

Changes in Arasan 15.1:
1) Correctly parse Winboard "level" command that includes a fractional
part in the time increment.
2) Fix bug in result learning code: incorrect learn value when drawing
a high-rated opponent as Black.
3) Fixes to eval for potential passed pawns. Small increase in castling
scores.
4) Changes to "trade down" material scoring.
5) Remove a redundant check for moving a pinned piece when searching
checks in q-search.
6) Fix UCI multipv output when there are fewer legal moves than the
specified multipv count.
7) Change max hash table size for GUI.

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

Any improvement in strength from 15 to 15.1 ??

Works nicely as computer partner. Have been using it under Hiarcs Chess Explorer GUI (playing Arasan and analyzing games with Hiarcs). It can be adjusted for rating in the 1000-2600 range, in 25 points intervals. Since it has a good and varied opening book and the Elo rating values well set, it is enjoyable to play with. Arasan is a nice work, congrats.

@Fauzi wrote:Any improvement in strength from 15 to 15.1 ??

No, there is no improvement

CEGT 40/40 Rating List

Arasan 15.1 x64 1CPU 2551
Arasan 15.0 x64 1CPU 2549

http://www.husvankempen.de/nunn/40_40%20Rating%20List/40_40%20BestVersion/rangliste.html

I wonder why Arasan (one of my favourite engines) had never had any good improvement since version 8-10 till now 15.1 , :( , all my respect Jhon Dart I wish You the best for the future

Arasan 15.1 JA (Android)
https://dl.dropbox.com/u/5047625/arasan-15.1-android-ja.zip
Unzipped direct download > https://dl.dropbox.com/u/5047625/arasanx

Arasan 15.2 is available

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

1) Some speed improvements especially when multithreaded.
2) Code cleanup and bug fixes related to draw handling (could lose on
time in server games, in rare cases, due to problems in this area).
3) Some more code conversion to C++ style intead of C. Use STL pair template.
4) Minimum search time changed to 10ms to better support very fast test
games.
5) Bug fix in code for checks in qsearch: ensure checking moves do not
place own king in check.
6) Some weights changed in scoring module based on CLOP.
7) Simplified razoring code.
8) Qsearch forward pruning changes. We use only pre-selection of captures now, not traditional forward pruning. Margins for this adjusted.
9) Linux-specific bug fix for occasional crashes when >2 threads in use.
10) Fix in aspiration window code for rare overflow condition when
failing low with a mate score.
11) Fix bug setting hash sizes > 2GB through Winboard/UCI.
12) Somewhat more general Rook pawn vs wrong color Bishop draw detection.
- This version is measurably stronger than 15.1 but nothing dramatic: I think around 20 ELO.