Pawn Storm - Theory
Posted: Wed Feb 14, 2018 5:58 pm
Here is an outline for the theoretical conditions for a pawn storm:
(1) Queen participation is necessary in a pawn storm attack. Take the queens off in this position and the pawn storm attack fizzles to nothing. Minor material is also important. The pawn storm attack weakens with less material. Take the minors off the board in the same position and the attack weakens.
[d]1k1r1r2/1ppq4/p1p1bp2/4p1pp/1Q2Pn2/3PNN1P/PPP2PP1/R4RK1 w - g6 0 17
(2) Development of attacking material is necessary before beginning a pawn storm on the king position. To estimate this, test a castling complete status flag. Otherwise, the defending king could castle to the opposite side of the board and out of trouble. However, once a side has castled, the king is free to wander back to the center of the board. After development, the king positions can be zoned to either the left or right side of the board.
(3) Challenge kings with some other piece beside the pawns. The pawns themselves cannot threaten the king. Test a king safety value. Otherwise, the pawns are over-extending and will be subject to attack. The early advance of pawns is a commitment to sacrifice of material at some point. Pawns will be picked off that threaten for too long without advancing. Another way of expressing this is to say there are multiple attacks on the horizon.
(4) Pawn storms are best when kings are on the opposite sides of the board. A pawn storm can still take place with kings that have castled on the same side. However, king safety of the attacking side is compromised once the king pawn structure has been weakened by advancing pawns. If a same side king pawn storm succeeds, it is more likely because of other tactical issues.
(5) Connected pawns can increase the strength of a pawn storm.
Blocked pawns are slightly less active than free pawns (or pawns that can advance). However, tuning blocked values appear unstable between a bonus and a penalty. Other dynamics are more important. Stockfish 9 adds a blocked/unblocked pawn value but that seems too hopeful. The mapped values are similar.
Pawns Storms are part of opening theory because they are effective with lots of material, Queen attacks, castling status, and the sacrifice of material for attack. The engine is calculating pawn storm structures very early in the search. Passed pawns are less an issue as it would be in the endgame.
There are different types of pawn structures not considered that might be called pawn storms. First, there is pawn shelter and how the shape of the defensive pawns may effect the safety value. That is a very complex polynomial problem. King safety should have already calculated some sort of pawn defect around the attacked king. This part only examines the attacking pawns. Second, a positional crush is different from a king side pawn storm. In the board below, blacks problem is lack of mobility. Therefore, additional pawn attack information is unnecessary. The black king is safe. The white pawns are squeezing, not sacrificing. If the position gets bad enough, black could end up in zugzwang - or tempo obligation to move.
[d]rnr3k1/1p1b1p2/4p1p1/1PPpP2p/pB6/3B4/5PPP/R4RK1 w - - 4 23
Stockfish 9 considers a pawn storm on the opposite side of the king position. This is a different type of pawn structure. This can take place during the endgame but the expectations are different. In the endgame, the idea is to keep the pawns as long as possible and to queen at least one of the pawns. In an early king safety pawn storm, the expectations are to sacrifice the pawns with material loss and for a mating attack or positional trade. It is possible to combine different concepts into a single table as SF9 does, but there is no advantage in doing so.
Pawn storms are rare but damaging when they do happen. The main idea is to prune occurring positions in the tree rather than evaluate a pawn storm as a root principal variation. This leads to a different kind of problem when adding pawn storm code (or any type of code than tries to define a series of conditions). Consider the following obscure position that occurs in the search tree. The pawn storm attack on c6 is a useless calculation:
[d]r2k1bnr/ppp1pppp/2P5/8/2q5/8/PPPPNPPP/RNBQ1K1R b - -
Unfortunately, this type of position is too common in the opening tree. The kings are wandering around in the opening because they are trying to escape the pre-programmed king safety problems. Fixing shortfalls in a chess program is sometimes like trying to plug a leak. Fix one leak, and six more leaks suddenly appear.
(1) Queen participation is necessary in a pawn storm attack. Take the queens off in this position and the pawn storm attack fizzles to nothing. Minor material is also important. The pawn storm attack weakens with less material. Take the minors off the board in the same position and the attack weakens.
[d]1k1r1r2/1ppq4/p1p1bp2/4p1pp/1Q2Pn2/3PNN1P/PPP2PP1/R4RK1 w - g6 0 17
(2) Development of attacking material is necessary before beginning a pawn storm on the king position. To estimate this, test a castling complete status flag. Otherwise, the defending king could castle to the opposite side of the board and out of trouble. However, once a side has castled, the king is free to wander back to the center of the board. After development, the king positions can be zoned to either the left or right side of the board.
(3) Challenge kings with some other piece beside the pawns. The pawns themselves cannot threaten the king. Test a king safety value. Otherwise, the pawns are over-extending and will be subject to attack. The early advance of pawns is a commitment to sacrifice of material at some point. Pawns will be picked off that threaten for too long without advancing. Another way of expressing this is to say there are multiple attacks on the horizon.
(4) Pawn storms are best when kings are on the opposite sides of the board. A pawn storm can still take place with kings that have castled on the same side. However, king safety of the attacking side is compromised once the king pawn structure has been weakened by advancing pawns. If a same side king pawn storm succeeds, it is more likely because of other tactical issues.
(5) Connected pawns can increase the strength of a pawn storm.
Blocked pawns are slightly less active than free pawns (or pawns that can advance). However, tuning blocked values appear unstable between a bonus and a penalty. Other dynamics are more important. Stockfish 9 adds a blocked/unblocked pawn value but that seems too hopeful. The mapped values are similar.
Pawns Storms are part of opening theory because they are effective with lots of material, Queen attacks, castling status, and the sacrifice of material for attack. The engine is calculating pawn storm structures very early in the search. Passed pawns are less an issue as it would be in the endgame.
There are different types of pawn structures not considered that might be called pawn storms. First, there is pawn shelter and how the shape of the defensive pawns may effect the safety value. That is a very complex polynomial problem. King safety should have already calculated some sort of pawn defect around the attacked king. This part only examines the attacking pawns. Second, a positional crush is different from a king side pawn storm. In the board below, blacks problem is lack of mobility. Therefore, additional pawn attack information is unnecessary. The black king is safe. The white pawns are squeezing, not sacrificing. If the position gets bad enough, black could end up in zugzwang - or tempo obligation to move.
[d]rnr3k1/1p1b1p2/4p1p1/1PPpP2p/pB6/3B4/5PPP/R4RK1 w - - 4 23
Stockfish 9 considers a pawn storm on the opposite side of the king position. This is a different type of pawn structure. This can take place during the endgame but the expectations are different. In the endgame, the idea is to keep the pawns as long as possible and to queen at least one of the pawns. In an early king safety pawn storm, the expectations are to sacrifice the pawns with material loss and for a mating attack or positional trade. It is possible to combine different concepts into a single table as SF9 does, but there is no advantage in doing so.
Pawn storms are rare but damaging when they do happen. The main idea is to prune occurring positions in the tree rather than evaluate a pawn storm as a root principal variation. This leads to a different kind of problem when adding pawn storm code (or any type of code than tries to define a series of conditions). Consider the following obscure position that occurs in the search tree. The pawn storm attack on c6 is a useless calculation:
[d]r2k1bnr/ppp1pppp/2P5/8/2q5/8/PPPPNPPP/RNBQ1K1R b - -
Unfortunately, this type of position is too common in the opening tree. The kings are wandering around in the opening because they are trying to escape the pre-programmed king safety problems. Fixing shortfalls in a chess program is sometimes like trying to plug a leak. Fix one leak, and six more leaks suddenly appear.