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descriptionEthereal EmptyEthereal

Homepage :

UCI compliant chess engine which uses a BitBoard board representation.
Estimated ELO : +/- 1950

Build of revision 626
Windows build :

Linux build :
To make the binary executable(Permission denied error) : chmod a+x ethereal-rev-626-linux64

descriptionEthereal EmptyEthereal Bitboard 6.26 Chess Engine.....very nice!!

A new chess star is born…Ethereal 6.26 (Bitboard) chess engine…..happened by chance to spot this chess engine last weekend and downloaded a copy and did not expect much as I had never heard of it…..figured it might not even waited a few days and played around with it trying to see if it would work….added a couple of files libstdc++-6.dll (0.97mb) and libgcc_s_sjlj-1.dll (113k) and to my surprise the engine began to work…but does it even play chess moves? Loaded it into lokasoft for a few RR games versus various engines…..and…it was MAGIC Not only did it play…the engine played WELL right from the beginning…..playing style was interested and some of the games were…..well….dynamic and profound….playing style reminded me of a strong “coffeehouse” chess player…strong early in the middle and endgame
Good combinational ability…only saw the engine castle once in about 25 games…lots of nice wins…artificial INTELLIGENCE….congrats to the engine designer…..whoever that may be Thanks to linuxchess for the compile….. thumb up bigsmile

descriptionEthereal EmptyEthereal rev. 695

Windows build compiled with Visual Studio 2015, statically linked.

Windows and Linux binaries :

descriptionEthereal EmptyEthereal rev. 715

Windows and Linux executables :

descriptionEthereal EmptyEthereal rev. 733

Output of engine time is now in milliseconds.
Engine searches deeper.
Smaller executable.
Strongest version till now.

Windows and Linux binaries :

descriptionEthereal EmptyRe: Ethereal

linuxchess wrote:
Output of engine time is now in milliseconds.
Engine searches deeper.
Smaller executable.
Strongest version till now.

Windows and Linux binaries :

Roughly how strong now?

descriptionEthereal EmptyRe: Ethereal

2200 ELO

descriptionEthereal EmptyEthereal 745


Last edited by linuxchess on Wed Jun 15, 2016 11:15 am; edited 1 time in total

descriptionEthereal EmptyRe: Ethereal

Not working for me in arena or winboard, seems stuck in analyze mode.

descriptionEthereal EmptyRe: Ethereal

not working in fritz

descriptionEthereal EmptyEthereal 745 windows build fixed

version 745

Windows + Linux + Android builds :

descriptionEthereal EmptyEthereal 7.49

Windows 64 build :

Linux 64 build :

Latest Android build :

descriptionEthereal EmptyRe: Ethereal

Still not moving when playing match. giving out move info like analyse mode, but not making moves................

descriptionEthereal EmptyRe: Ethereal

joechess wrote:
Still not moving when playing match. giving out move info like analyse mode, but not making moves................

That is odd. Moves here.

descriptionEthereal EmptyEthereal 7.61

Version 7.61

Many improvements.
Code cleaned up.
Removed all compiler warnings for -Wall -Wextra -pedantic -std=c99
Removed all the static declarations in headers which were bloating the cache
Fixed extra variable bugs throughout
Fixed an issue with evaluatePawns()
Fixed an issue where promotions where delta pruned in the qSearch
Scaled up the values for Passed Pawns. Now different for mg/eg
Small speed up for evaluateRooks()
Added ROOK_ON_7TH values
Adjusted ROOK_OPEN_FILE values to scale better with phase

ELO rating : 2500

Windows executable :

Linux executable for processors with popcount instructions :

descriptionEthereal EmptyRe: Ethereal

Ethereal 7.70

descriptionEthereal EmptyEthereal 8.00

Ethereal 8.00

Summary of the changes made.
Cleaned up a large portion of the source code, removal of magic numbers + more
Resolved an issue which could cause problems with repeating time controls
Fixed an issue where not all squares could be connected (Thanks, Fernandotenorio)
Fixed an asymmetry issue with pawn connect evaluation (Thanks, Fernandotenorio)
Added Queen mobility into the evaluation function
Pawns can now be both stacked and isolated
Apply LMR to PV nodes but at a reduced depth
Factoring in pawns into attackerCounts and attackCounts
Lowered the threshold of attackers for the safety table
Greatly simplified the evaluation function, and merged most code together
Began saving passed pawn locations into the Pawn Structure transposition table
With that addition, we are now able to score passed pawns based on other features on the board
Extended a max depth limit from 32 to 64.
Factoring in all 'standard' terms into the zorbist hash
Fixed an issue where castle moves were generated when there were none
Cleaned up some code involving making null moves
Simplified the transposition table now that turn is factored into the zorbist key
Finally removed the damned -MATE scores
Finally created a nice testing framework, EtherealBenchmarking

Downloads :
Android :
Windows64 :
Windows32 :

descriptionEthereal EmptyRe: Ethereal

Ethereal 8.05

descriptionEthereal EmptyRe: Ethereal

Ethereal 8.62

descriptionEthereal EmptyRe: Ethereal

Ethereal 9.00

From the author:

Hello Again Everyone,

Today I am announcing the release of Ethereal9.00. It's been a wild ride since
adding lazy SMP a few months ago in order to participate in TCEC. A big thanks
to Knight Moves and Anton for having me. It's provided inspriation for a few
patches, and for a handful of bug fixes.

Link to the Github Release Page:

Link to the Talk Chess Release Page:

Link to the 64bit Windows Binary:

Link to the Android Binary:

Link to a MAC Binary: If someone will provide one :)

Everytime I take a guess at the elo gains it comes back to bite me, so I'll just
say this; Ethereal is a hell of a lot better with you throw many cores at it. In
fast testing with 4CPUs I am seeing over 250 elo. Obviously that number will not
hold in CCRL conditions, but I expect this version of Ethereal will perform far
better than Ethereal8.61 in conditions like TCEC with 43 cores to work with.

Here is the recap for changes since 8.61, for those interested:
8.61 : Fix a bug with how the main scheduling lock was setup
8.62 : More aggressive time allocation in X/Y games
8.63 : Allow the aspiration window to be as small as [-1, 1]
8.64 : Again more aggressive time allocation in X/Y games
8.65 : Penalty in the eval for a queen attacked by a pawn
8.66 : Prune weak captures that are likely to fail in QS, with
a short / cheap version of SEE. Idea by Dennis Sceviour!
8.67 : Don't apply the weak capture pruning to promotion moves
8.68 : Better time managment in X+Y and X/Y games
8.69 : Introduction of ProbCut, inspired by the Stockfish implementation
8.70 : Apply the weak capture pruning in the search as well as qsearch
8.71 : More aggressive use of weak capture pruning in the search (depth 5)
8.72 : Allow ProbCut to refute a null move (Unlike SF)
8.73 : Allow for a different upper and lower margin on the aspiration window,
by looking at the last 3 search scores. Minumum bound is 4. I believe
this idea is unique to Ethereal -- at least I have never seen it elsewhere
8.74 : Bonus for Pawns and Minors in the King's Safety Area
8.75 : Fix an issue where helper threads were able to allocate more search time,
such that with many threads the max time would be used with every move.
This was found thanks to TCEC, and was worth ~70 ELO in selfplay
8.76 : Take a guess at the time of the next search and consider stopping now
8.77 : Lower base time usage, and allow for much more massive time allocations
8.78 : Add an official Logo for Ethereal, created by DanishStyleFetta!
8.79 : Clean up some threading code (reduce LOC) and allow for max depth of 128
8.80 : Fix a bug where all helper threads would always use the aspiration window
centered around the value zero. This was worth ~80 ELO in selfplay
8.81 : Skip Weak Capture Pruning when in check
8.82 : Implement a basic form of Pawn/King Shelter
8.83 : Use a generalized Piece Square Table for sorting quiet moves
8.84 : Penalty for Minors attacked by Pawns
8.85 : Do not place any value on the R value for Null Move Pruning
8.86 : New time allocation scheme to unify X+Y and X/Y (later reworked...)
8.87 : Resolve a bug where Ethereal could, on very rare occasion, play an illegal
move as a result of the PV not being filled AT ALL, even in the root node
8.88 : Allow beta pruning (static null / futility) when we only have Pawns
8.89 : When doing early pruning (NMP, Razoring, Static Null, and Probcut), always
return alpha or beta. The goal was to make more conservative TT entries
8.90 : Lower the margin for futility pruning / beta pruning to about one pawn
8.91 : Make Ethereal's history counters more like the Stockfish history counters
8.92 : Yet another patch to allow for more aggressive time allocation
8.93 : (CURRENT TM) Allocate three things, an ideal usage, a max usage, and a max
alloc. We will NEVER exceed max usage, and will never start another iteration
after exceeding max alloc. Overtime we adjust a score and pv stability factor
to increase or decrease allocated time with respect to pv stability and scoring
8.94 : Fixed an issue with true-sharing of the transposition table used counter. Now
we sample the first entries in the TT and approximate the hashfull. This was a
huge elo winner with high thread counts
8.95 : Increase base LMR value by one, and reduce it by one when the best move is
a quiet move and the TT move has failed or this is our first quiet attempts
8.96 : Cleanup of capture value pruning decisions and some inconsitencies
8.97 : Remove a pointless flag from the makefile, thanks Laldon!
8.98 : New method of Pawn/King Shelter definition. Before we would be okay with a
King pushing past his pawns, so long as they were still close
8.99 : One big fat tuning patch to update everything the last tune
9.00 : Cleanup the Texel Tuning implementation by using about 10% of the memory
as before, resulting in a 700% speed up in a quick test of tuning

Thanks to everyone who has taken an interest in Ethereal over the last few months.
The ideas and suggestions from the TCEC chat have been incredible.
And, as always, thank you to the testers :)

Andrew Grant

descriptionEthereal EmptyEthereal 9.00


Making a chess engine : a work without end... pure addiction! :)

descriptionEthereal EmptyRe: Ethereal

Ethereal 9.30

From the author:

Hello once again. It's only been about a month since I posted the
release of Ethereal9.00, but I think I have made enough gains since
to warrant a new release. I've made a fair number of improvements with
the evaluation, as well as the tuning process behind it. Some search
changes have been made, but mostly speedups and a few parameter tweaks.
As for SMP, nothing has been changed, although not for a lack of trying.
Time management has been as issue as well, or so was reported to me when
watching some of Graham's tournament games. I have made one fix which
should help that issue out, but nothing too ground breaking.

The release on Github can be found here, and has a Win64 and android binary.
Win64 binary is non-popcount and non-bmi2, so I expect it to work for everyone.

Since Ethereal9.00 I've had some help from someone named Laldon, a
follower of TCEC. He provided a great deal of CPU power for some of
these tuning sessions, and identified a very large bug in the Tuner.
He has given me a handful of other patches to try, mostly dealing with
imbalances. We've not gotten them to work yet, but his input and his ideas
are very valuable. Patches that he submitted, or that he suggested /
played a role in are marked in the change log with a *

Some results to give an idea of how much stronger Ethereal is now.
I expect many of the lowest time control scores to be inflated. I
made many changes which provide reasonable speedups, which of course
scale away as the time control increases.

Ethereal 9.30 vs Ethereal 9.00: 450 - 182 - 368  [0.634] 1000 +95 @5s.05s 1-CPU 2MB-HASH
Ethereal 9.30 vs Ethereal 9.00: 375 - 153 - 472  [0.611] 1000 +78 @20+.2s 1-CPU 8MB-HASH

Ethereal 9.30 vs Laser1.5: 384 - 308 - 308  [0.538] 1000 +26 @5s.05s 1-CPU 2MB-HASH
Ethereal 9.30 vs Laser1.5: 408 - 400 - 442  [0.503] 1250 + 2 @20+.2s 1-CPU 8MB-HASH

descriptionEthereal EmptyRe: Ethereal

Ethereal 9.65
This is an official release!
The latest release Ethereal 9.71

descriptionEthereal EmptyRe: Ethereal

Ethereal 10.55

descriptionEthereal EmptyRe: Ethereal

Ethereal 11.00

Up to 70 Elo stronger.

descriptionEthereal EmptyRe: Ethereal

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