# Draw Evaluation

Home * Evaluation * Game Phases * Endgame * Draw Evaluation

It is important for the evaluation function to recognize the endgame positions which are likely drawn, even though one side has a nominal advantage. This page is devoted to listing some of them. More of that kind of knowledge can be found in the KPK section.

# Obvious Draws

According to the rules of a dead position, Article 5.2 b, when there is no possibility of checkmate for either side with any series of legal moves, the position is an immediate draw if

• both sides have a bare king
• one side has a king and a minor piece against a bare king
• both sides have a king and a bishop, the bishops being the same color

# Simple Heuristics

The bishops of different colors are not counted as an immediate draw, because of the possibility of a helpmate in the corner. Since this is unlikely given even a four ply search, we may introduce another class of drawn positions: those that cannot be claimed, but can be evaluated as draws:

• two knights against the bare king
• both sides have a king and a minor piece each
• the weaker side has a minor piece against two knights
• two bishops draw against a bishop
• two minor pieces against one draw, except when the stronger side has a bishop pair

Please note that a knight or even two knights against two bishops are not included here, as it is possible to win this ending.

Implementation note: When a program uses heuristics of that kind, it is of utmost importance to be consistent. For example, if KBN vs KB is scored as a draw, the same must be done with KBN vs KBP. A possible idea is to divide a score by a large constant, such as 16 or 32, when the side nominally ahead has the wrong piece combination.

# One-sided Heuristics

There are some heuristics that tells us only that one of the players cannot win the endgame

• a single minor piece should not win against any number of pawns (again, there is a special case of a smothered mate in the corner, but it is search issue, not to be taken into account by the evaluation function)

# Forum Posts

## 2010 ...

Re: question on draw evaluation by Robert Houdart, CCC, June 07, 2010