The author of PGG106, is making his Alexandria chess engine available as a free, open-source engine under the GPL3.0 license.
Alexandria is relentlessly and piercingly breaking into the top of the strongest.
According to the MCERL rating list, Alexandria 5.1.1 (the December 2023 version) is playing at 3616 Elo, matching such heavyweights as RubiChess, Clover and rofChade released in the same year, for example.
Source: MCERL
The author decided quite quickly to use a neural network. Already from the second version, Alexandria played implemented NNUE, which allowed to strengthen the playing power of this engine about 600 Elo (!)
Source: MCERL (ongoing)
Of course, the strength of the chess engine is not only the neural network, as was clearly evident from the successive versions published by PGG106.
As of May 2022, 17 more versions of this chess engine have been released. Alexandria has been and continues to be developed in every aspect, which has led to a clear increase in the power of the game.
Noteworthy is the author's ability to work effectively with talented creators, which perfectly underlines the fact that Alexandria's power has grown so impressively.
What particularly caught my attention while observing Alexandria's games and analyzing chess positions was this engine's extraordinary determination to achieve a positive result. Whether having an advantage, looking to equalize, or fighting to save the game,
Alexandria showed "claw" by finding often risky and working continuations.
At such a high as reaching 3600 Elo in games between chess engines, the concept of risk is extremely rare. For the most part, chess engines playing at this strength easily outplay the weaker ones and draw against engines of similar playing strength. This is not what Alexandria does - and it is what sets this excellent chess engine apart.
I invite you to read some examples.
1.
White: Vafra-14.12, which is a clone of one of the strongest - Stockfish. Without a doubt, it is an engine capable of winning against any other.
Black: Alexandria 5.1.1
Black's move.
Quite a dynamic situation on the chessboard, full of pieces.
Vafra, without the slightest qualms, has been building his advantage since the beginning of the game. Currently, it has 1 pawn more and is trying to consolidate its forces. The last move of the white pawn to Vafra's h4 square is an intention to place the white knight on the g5 square, which will allow it to occupy a perfect area close to the black king and limit the freedom of movement of the black queen.
If Alexandria does not take any decisive action, then most likely the result of this game will end in defeat.
What to do? It seems that the black figures stand in quite optimal positions, while the white's zone and its king are fortified and defended by numerous pieces.
33...Bxg3!!
Alexandria, does not wait for further and unfavorable developments - hits a strong point near the white king.
This is a risky and very unexpected move, the idea of which is to reverse the fortunes of this game. White must respond with precision.
34.fxg3?
Correct 34.Nxg3 sustained white's advantage giving them a chance to win.
White's move opens the way for Alexandria to strengthen his position and attack the white king.
34...Qe3+=
In the following moves there will be a series of exchanges, thus reducing the material on the chessboard.
The position is even, although Vafra probably doesn't see it yet.
35.Kh2 Rxf1
36.Rxf1 36.Be2
"Forks" - Alexandria with the intention of taking the white Bishop.
37.Re1 Qxd3 The forces have been aligned.
The first dust has settled. Let's take a look at the position on the chessboard.
If white makes the queen exchange (38.Qxd3), then they will be at a disadvantage, as they risk losing the weak pawn on the a6 field and, consequently, likely losing.
Vafra chooses the good 38.Qa2
A series of several moves follows. Both sides do not want to proceed to the endgame for the time being. Vafra is looking to position its white Knight on a good field, Alexandria is looking closely for a chance to escalate operations near the enemy King.
38...Bf3
39.Nf6+ Kg7
40.Nd7
Finally, the whites position their Knigt near the foreign monarch. Only, is the center of events right there?
As we'll see in a moment, probably not!
40...Re8!
Alexandria once again sacrifices material, this time at the cost of Rook, black wants to gain access to the first line on the chessboard to create strong threats.
White accepts the sacrifice. 41.Rxe8
41...Qf1
And the threat of the white king's checkmate.
It's easy to avoid this checkmate by 42.Re7+ or what white played
42.g4.
Black kills the pawn on g4, 42...hxg4.
White starts giving chess to the black King. Will this game end in a draw?
43,Re7+
43...Kg8
The situation seems clear, with each successive move bringing a draw closer, which I guess would be a dream outcome for Vafr in this game.
What next? Well, it's another check to the black King.
44.Re8+??
This seemingly innocent move leads to disaster for the whites.
It was necessary to 44.Kg3 maintaining the balance.
44..Kf7! -+
The draw was led to by 44...Kg7 and 44...Kh7.
45.Rf8+ Ke7
46.Rxf3
Forced to avoid checkmate.
46...gxf3
47.Kg3 d3
Nothing will stop one of the two black pawns on the 2nd line.
48.b5 Qe1+
49.Qf2 d2
The game continued for a few more moves and ended in victory for Alexandria.
This game, is such a characterization of Alexandria's playing style in the proverbial nutshell.
Determination, tenacity, risky decisions and iron consistency.
If such a game were played by human chess players, one could venture to say that white (Vafra) as a result of black's (Alexandria's) pressure lost his way completely and, being shocked after the white king's position was smashed (sacrificing black's Bishop 33...Bg3!!) led not only to the loss of the win, he even slipped away with a draw.
And all this during one game between engines playing at 3600 Elo level.
Below this game prepared for download.
2.
Another example, this time much shorter.
White: Dragon 3 by Komodo Chess, an engine that needs no introduction. One of the strongest until 2023.
Black: Alexandria 5.1.1
Sharp position on the chessboard. The black King is defended by two figures and a pawn, the white King is protected by three figures and a pawn. In the last move, white took the opponent's pawn on the b5 square. Dragon has two more pawns.
Black's move.
Let's see how Alexandria managed to save this game.
27...Rxc2+!
A nice sacrifice that immediately clarifies the situation on the chessboard. White will not escape the perpetual check.
28. Kxc2 Qc4+
29. Rc3 Qe4+
30. Kd2 Qg2+
31. Ke1 Qg1+
32. Ke2 Qg2+
33. Kd1 Qf1+
34. Kd2 Qf2+
35. Kd3 Qf1+
36. Kd2 Qf2+
37. Kd3 Qf1+
The game ended in a draw.
This is how Alexandria plays against a class opponent.
Below this game prepared for download.
3.
And another showdown between Dragon by Komodo Chess and Alexandria. This time, the result will not be as quick, but more impressive and victorious for Alexandria.
White: Dragon 3.1 by Komodo Chess
Black: Alexandria 5.1.1
Dragon presses on the Queen's wing. A strongly advanced white pawn on the a6 field does not herald anything good for black. On the other hand, the white King's wing shows no possibility of attacking his positions. Seemingly...
As you may have already noticed, dear reader. Alexandria has the skills to successfully solve problems on the chessboard.
Black's move.
22..Bxh3!!
What a hit :)
For most chess engines, this move is difficult to find in a short time.
If Dragon does not accept this sacrifice, his position will immediately deteriorate significantly.
23.gxh3 Qc8
The Black Queen targets the h3 square, close to the enemy King.
24.N1d2 Qxh3
25.Nxe4
White moves his Knight to defend the King.
25...Qg4+
26.Ng3
With the intention of directing the Queen to the e2 square.
26...Rf3! -+
Confirms the decisive advantage of black.
27.Qb4
Dragon proposes an exchange of Queens, to which, of course, it does not receive permission.
27...Nc4
White can't avoid heavy material losses to avoid the checkmate. Dragon gives up his Queen for a black Knight.
28.Qxc4 Qxc4
After further heavy material losses for the whites, the game ended with Alexandria winning.
Below this game prepared for download.
And how does it fare against others ?
4.
White: Alexandria 5.1.1
Black: Berserk 11, an extremely powerful chess engine, one of my favorites.
Using this last presented game as an example, I will show how mature and powerful Alexandria is. One inaccurate play by black, allowed Alexandria to spread its wings of initiative and obliquely exploit every opportunity it encountered. This led to Berserk's defeat.
In the diagram below, we see the situation on the chessboard right after the Spanish opening was played. A cool and interesting position in which each side has its chances for a favorable result.
White's move.
22.Bd4
White starts by positioning his pieces on every better square. Bishop on d4 controls the longest diagonal.
22...Nd7
Black positions his Knight so as to direct it to the center of the chessboard in the future.
What follows is a series of maneuvers to regroup forces from both sides.
23.Ra7 g6
24.Qd2
24...Nc5?!
Inaccurate play.
Better 24...Ne5 defending the pawn on f7 or 24...Qh4 controlling the f4 square.
25.Qf4
Precise and timely.
25...Be7?!
Again, inaccurate. This Bishop should defend the black King in the future by staying on the f8 square or heading to the g7.
Better 25...Bd7 blocking the way to the f7 square.
26.Nf5!
Just like that.
Berserk accepts the sacrifice of the white Knight, otherwise checkmate in several moves.
26...gxf5
27.Re3
White Rook joins the attack on the position of the black king.
27...Bg5
Berserk enlists the active defense of its black-field Bishop backed by the Queen.
28.Rg3
28...Ne6
29.Qxf5
29...Rc7
All forces to defend.
30.Bf6
The culmination of the attack on the black King's positions.
30...Qxf6
Berserk gives up the Queen for the white Bishop and Rook.
31.Qxf6
31...Rxa7
32.h4
Black will soon lose Bishop on the g5 square.
In the long run, black has lost another pieces. Berserk defended bravely, but failed to turn the game around.
The game ended with Alexandria winning convincingly against a challenging opponent.
Below this game prepared for download.
Alexandria is one of the biggest and positive surprises among chess engines in 2023!
What deserves special praise is that Alexandria is written in such a way as to seamlessly prepare this chess engine to run on different platforms.
For this, I am grateful and thank the author on behalf of Chessengeria readers who use mobile devices and those running on Linux, Macs and Windows.
I encourage you to download and try Alexandria, a modern and powerful chess engine.
Feel free to download the Alexandria chess engine.
Android – Compiled by Archimedes
Linux arm64 & x64 – Compiled by Darius
Mac Apple Silicon & Intel – Compiled by Darius
Windows x64 – Compiled by Darius
* Diagrams created in the ChessX.