A theoretical exercise...

[BFG]

It is obviously an impossibility to know this for certain; I'm just curious as to what others would guess.

If one were to look at the entire history of computerized chess, regardless of platform, hardware, geography, etc....how many different publicly released, stable series would you guess have existed?

(By "series", I mean that all versions of a given engine would be counted once - Houdini 1.5 32-bit and Houdini 4.0 64-bit together would only count once. But Ivanhoe, being a renamed derivative of Ippolit, would be counted separately. Series like ChessMaster get a bit murkier because, while they all share a name, not all of the engines are related to each other.)

[Kirill Kryukov]

Here is one relevant chart: http://rwbc-chess.de/Additional/chronology.htm

I think there should be more than 1000, just counting engines. Much larger number if you also counted non-engine chess program, including those for all obscure and ancient devices. (Also, it will depend a lot on your definitions of "stable", "public" and "different").

[BFG]

It's amazing how much chess engines have proliferated since 2005. I suppose the Kasparov-Deep Blue matches inspired many chess lovers/programmers to see how strong of an artificial opponent they could create. Heck, I'd love to try creating a chess engine too, but though I can program in 3 languages, I'm very doubtful I could ever produce something of a Houdini or Stockfish quality (or, for that matter, even make it halfway up the CCRL's list!)

Anyway, thank you for this link...it was very interesting and informative.