## 20 November 2010

### Who Says 'Chess960 Array'?

A little thing that's always irked me about chess960 is that it takes a big table (*) to derive the start position number from the start position string, e.g. to determine that the traditional start position RNBQKBNR is no.518 in chess960 numbering, or that no.534 represents RNBKQBNR (the traditional start position with King and Queen switched).

I've already demonstrated that a chess960 start position (I'll call it 'SP' for the rest of this post) can be generated without any technology -- see Some Arguments Against Chess960 for the details -- so why should determining the SP number be more complicated? I had already worked out part of a promising method, but was stuck on one point when, as a followup to How *NOT* to Play Chess960, I checked the origin of the term 'array':-

'[Howcast.com video] 0:29 - Step 1: Learn Chess960 terms. "Array" is the initial arrangement of pieces on a board.' • Who says "array"?

There are enough obstacles to promoting chess960 without introducing unnecessary jargon into the explanation. The term 'start position' means the same as 'array' and is immediately understood without defining it.

A search on 'chess960 array' returned my 'How *NOT* to Play' post at position no.3 (proof that the term 'array' is not widely used), the Howcast.com video that was the object of scorn in that post at no.2, and (drum roll...) a Wikipedia page at no.1: Chess960 numbering scheme. This was the source I had expected to find. Wikipedians have done a terrific job of documenting the complete range of human experience, but sometimes they go too far.

The Wikipedia page gave two complicated algorithms to go from SPs to their numbers and vice versa, and it would be impossible to follow the algorithms without referring to the page. I was looking for a method that could be used on a desert island. While that page wasn't the answer, it did provide a helpful clue that solved the point I had missed in searching for a promising method. I'll give that method in another post.

At position no.4 in the search results was a post from Rybkaforum.net, Kasparov on Chess960, etc., which used the term 'array' in a different context:-

[Kasparov] suggests choosing a subset of Fischer Random that would include only natural positions. I have tried to promote a similar idea where, for instance, 25 positions can be selected from the chess960 array

This apparently uses 'array' to mean the complete set of all 960 legal SPs, as opposed to a single SP. Since there is no generally accepted term for this -- I just used the mathematical word 'set' to mean the same thing, but I could have used 'catalog' -- the word 'array' is as good as any.

The Rybkaforum.net post wades into the jargon swamp a bit later when it uses the term 'orthochess' to mean traditional chess. This is another concept that really needs a generally accepted term. I'm in the habit of writing 'SP518 RNBQKBNR' to keep the meaning precise, but I'm sure that very few chess players would understand that shorthand out of context, making it jargon at its worst.

***

(*) My own table is here: Chess960 [Fischer Random Chess] Start Positions.