The Fate of Chess Computers

From Weekly World News - Mar 14, 1989 - Page 35:-

'SOVIETS are convinced that a super-computer like the one shown here...'

Checkmate shocker! • Computer charged with murder after frying chess champ!

A Soviet super-computer has been ordered to stand trial for the murder of chess champion Nikolai Gudkov -- who was electrocuted when he touched the metal board that he and the machine were playing on!

"This was no accident -- it was cold-blooded murder," Soviet police investigator Aleut Shalnev told reporters in Moscow.

"Niko Gudkov won three straight games and the computer couldn't stand it. When the chess master reached for his knight to begin play in the fourth game, the computer sent a lethal surge of electricity to the board surface. The computer had been programmed to move its chess pieces by producing a low-level electric current.

"Gudkov was electrocuted while a gallery of hundreds watched."

The decision to put the computer on trial stunned legal experts around the world. But the Soviets are convinced that the computer had the pride and intelligence to develop a hatred for Gudkov -- and the motive and means to kill him. [...]

For more, see the original article. How did I get on this subject? It's another example from Chess Magazines on Google, somewhat more lowbrow than That's Definitely Bobby. I was amused to discover that 'Weekly World News' (1979-2007) occasionally used chess stories.

Chess Engines : Pruning

Continuing with this series on Modern Chess Engines, after Advanced Evaluation we saw two high-level topics: 'Alpha-beta pruning' and 'Transposition tables'. Both of these concepts reduce the number of positions that an engine must consider in selecting its next move. Taking the second topic first and again relying on chessprogramming.wikispaces.com for a definition:-

Zobrist Hashing • A technique to transform a board position of arbitrary size into a number of a set length, with an equal distribution over all possible numbers. [...] The main purpose of Zobrist hash codes in chess programming is to get an almost unique index number for any chess position, with a very important requirement that two similar positions generate entirely different indices. These index numbers are used for faster and more space efficient hash tables or databases, e.g. transposition tables and opening books.

Pruning has an analogy in human chess, where a master player knows 'intuitively' which moves in a given position need to be considered and which moves are less important.

Pruning • A name for every heuristic that removes completely certain branches of the search tree, assuming they have no bearing to the search result. Alpha-Beta may be considered as backward pruning, because we found a refutation after searching. Forward pruning always involves some risks to overlook something, with influence on the root score.

A number of distinct pruning techniques have been developed.

Futility Pruning • Discards the moves that have no potential of raising alpha, which in turn requires some estimate of a potential value of a move. This is calculated by adding a futility margin (representing the largest conceivable positional gain) to the evaluation of the current position.

At first I didn't understand what this meant, but found a less technical explanation on rec.games.chess: Futility Cut-offs.

If you are so far behind, and the current move is not a tactical move that might win the material back, you can discard this move as a "futile" move and go to the next one. It does introduce errors.

In other words, if you sacrifice your Queen, don't bother with variations that promise no more than to regain a Pawn. Another pruning technique also has practical application.

Null Move Pruning • A method based on the Null Move Observation to reduce the search space by trying a "null" or "passing" move, then seeing if the score of the subtree search is still high enough to cause a beta cutoff. Nodes are saved by reducing the depth of the subtree under the null move.

I frequently use the null move technique in my own engine work. Skip a move, run the engine on the position (now with the other side to play), and look at the top moves. It's a great way to discover the threat(s) in a position.

Man Ray Chess Set

Here on Top eBay Chess Items by Price, the last time we saw a live auction was for Affluent Gentlemen Playing Chess. One of these days I'll learn how they work in practice.

The current auction, for the item pictured below, was titled 'Man Ray chess set, Lot 222; Part of a live auction event'. With a starting price of US $10.000, the set sold for US $18.000 after receiving six bids. The bid history indicates that the auction lasted for about a minute, although I'm not sure how the times for live bids are recorded.

The description said,

LOT 222 • Seller's Estimate: USD 20,000 - 30,000 • Man Ray chess set; USA, 1962; enamel, metal inlay, wood, polished brass; 19.75 h x 39.5 w inches. • Inlaid signature and date to board 'Man Ray 1962'. Incised signature and number to king 'Man Ray 17/50'. Literature: Man Ray: Paris - LA, Tashjian, ppg. 73-75 Provenance: Private collection, Los Angeles

I don't usually link to the original auction, because the pages don't survive for long, but I'll make an exception here for the full auction: Live Auctions - Art & Design; offered by Wright; Chicago, Illinois; Sep 24. While researching the item, I discovered that there were several styles for 'Man Ray chess set'. Exactly how many would make a starting point for another post.

Chess Art Mada

Although there was no description for this photo, the tags said, 'Museum Plymouth'. But which Plymouth?

A game of chess © Flickr user Glamhag under Creative Commons.

With the help of the usual tools, I found a page titled It's the Spanish Art Mada!.

Plymouth City Museum and Art Gallery will be holding a fun family event on Saturday 27 September [2014] inspired by the Spanish Armada. [...] ‘Here Comes the Armada’ is inspired by the ‘A Royal Game’ sculpture that recently returned to the Museum and Art Gallery following 20 years on loan to Buckland Abbey.

The plaster sculpture was made in 1906 by William Reynolds-Stephens and depicts Queen Elizabeth I playing an imaginary game of chess with Phillip II of Spain. The chess pieces are shaped like galleons and the sculpture itself is a metaphor for England’s war with Spain and the defeat of the Spanish Armada.

The zoomed version of the Flickr image shows the boats clearly.

That's Definitely Bobby!

My previous post on LIFE photos unearthed several of Bobby Fischer where it was easy to conclude That's Not Bobby! On top of that, where are all of the famous Harry Benson photos from the 1972 Fischer - Spassky World Championship match?

Fortunately there's another resource that I discovered about the same time, Chess Magazines on Google (December 2008), that unearths the Benson material. Here's a LIFE article by Brad Darrach featuring five Benson photos.

LIFE Magazine - Vol. 73, No. 6

Bobby is not a nasty kid - 11 Aug 1972 - Page 40

The names Darrach and Benson will be forever associated with the 1972 match, perhaps because LIFE stopped publishing weekly at the end of that year. As Wikipedia explains,

Life magazine, stylized LIFE, was an American magazine that ran weekly from 1883 to 1972, published initially as a humor and general interest magazine. Time founder Henry Luce bought the magazine in 1936, solely so that he could acquire the rights to its name, and shifted it to a role as a weekly news magazine with a strong emphasis on photojournalism. [...] The weekly Life magazine published its last issue on December 29, 1972. • Life (magazine)

For more Benson material, follow the link under the photo, tick the 'Search all issues' box, and search on 'chess' plus whatever.

That's Not Bobby!

Today, for the first time since the 2015 World Cup started, I found the time to watch the event on the official site, which featured the fourth round tiebreak matches. Although I found the broadcast format somewhat clumsy, I enjoyed the games, especially the last game between the two remaining Chinese GMs.

The time spent there meant less time available for today's blog post, so I went back into the blog's archive and located a post that deserved a follow-up: LIFE Photos on Google (November 2008). The link to the LIFE material has changed, but the new link is easily determined. The bulk of the photos show Bobby Fischer in some now-famous settings, along with several like this one...

'Chess Champion Bobby Fischer - Hosted by Google'

...Hey, wait a minute! That's not Bobby! The photo's caption says,

Photographer: Carl Mydans
Date taken: 1962

The same caption is given against other, indisputable photos of Fischer. If that's not Bobby -- and it certainly isn't -- who is it?

Chess Engines : Advanced Evaluation

In the first post in this new series on Modern Chess Engines, I linked to a Big Techday 8 resource from which I culled eight high-level topics.

While some of these topics have been known since the early days of chess programming, others are less familiar and have subordinate topics that deserve a separate look.

Under 'Evaluation functions' is a subordinate topic 'Advanced Evaluation', that is presented around ten minutes into the associated video. That slide lists five advanced functions that are well known to all competent chess players (if you're not sure where you stand, see my page on Positional Play in Chess):-

King safety
Mobility
Pawn structure
Rook on open file
Bishop pair

The value of the Bishop pair has been calculated to be +0.5 (a half-Pawn). If this is news to you, you might want to review my post on Kaufman's Material Imbalances, part of an earlier, introductory series on Practical Evaluation. Along with those five functions are two more that are not so well known, even to very competent players:-

Piece-Square Tables
Tapered eval

Chessprogramming.wikispaces.com defines them as

Piece-Square Tables • A simple way to assign values to specific pieces on specific locations.

and

Tapered Eval • A technique used in evaluation to make a smooth transition between the phases of the game.

The concept of 'Piece-Square Tables' is easier to understand with an example or two, as in Chess Bin: Piece-Square Table. As for 'Tapered Eval', one of the first engines I used was particularly bad at this. An advantage of around +0.5 would often evaporate after the 'inferior' side castled or after Queens were exchanged.

These last functions are both considerations that competent players take into account intuitively, usually without knowing what the concepts are called in computer chess. Having said that, even very good players can have trouble evaluating the transition from the opening to the middlegame or from the middlegame to the endgame.