A Pawn is doubled (or, sad to say, tripled) if there are more pawns of the same color on a given file. Early programs and papers advocated evaluation it as half a pawn, today the penalty uses to be less severe.
It might be argued that, given a perfect pawn structure evaluation, a term such as doubled pawns would not be needed, since they usually introduce another pawn structure weaknesses: some kind of backwardness, lack of a candidate passer that otherwise would be there etc. However, most evaluation functions do not go into such details as to justify removing this term.
Types of Doubled Pawns
| Hans Berliner characterizes doubled pawns by their exchange potential against opponent pawns on adjacent files :
The doubled pawns on the b-file are the best situation, the f-file pawns are next. The h-file pawns are the worst situation because two pawns are held back by one opposing pawn, so the second pawn has little value.
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| A doubled pawn of a so called "crippled" majority devalue that majority. Hans Berliner on following position in Some Innovations Introduced by Hitech :
Our pawn-structure algorithm is quite simple, detecting only isolated and multiple Pawns, and the effect of multiple Pawns on viable pawn majorities. For instance, in Diagram 1 the value of White's doubled Pawn is negligible, while Black's is almost full-valued. This distinction, an innovation, was first introduced in Patsoc , and we were able to adapt the code to make up tables to be loaded into six identical hardware units computing pawn structure in parallel.
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All About Doubled Pawns
- Doubled and Backward Pawn Engine "Definitions" by Brian Richardson, CCC, September 07, 2009
- passed but doubled pawns by Jon Dart, CCC, June 15, 2015 » Passed Pawn
- Doubled pawns by Stefano Gemma, CCC, May 11, 2016
- Hans Berliner (1999). The System: A World Champion's Approach to Chess, Gambit Publications, ISBN 1-901983-10-2
- Types of doubled pawns from Wikipedia
- Hans Berliner (1987). Some Innovations Introduced by Hitech. ICCA Journal, Vol. 10, No. 3, pp. 111-117
- Hans Berliner (1985). Computer Chess at Carnegie Mellon University. Advances in Computer Chess 4
- Larry Kaufman (2005). All About Doubled Pawns.