This package contains the sources of the XBoard-compatible Chess and
Chess-variant engine Fairy-Max, and its dedicated derivatives ShaMax
-(for Shatranj) and MaxQi (for XiangQi = Chinese Chess). A Makefile
+(for Shatranj) and MaxQi (for XiangQi = Chinese Chess). This version
+of Fairy-Max is actually a derivative, patched to evaluate pair
+bonuses and regognize drawish end-games. To distinguish it from the
+regular version it is renamed 'Pair-o-Max' A Makefile
is provided to compile and install them. Normally this would require only
the command (given from the main directory of the package):
to the gcc compilation command line.
+
+Pair-o-Max
+
+The heuristic used for recognizing drawish end-games works as follows:
+The evaluation score is divided by 2, 4, or 8 when the mating potential
+of the leading site is already non-existent, or is in jeopardy because
+the opponent can afford to sacrifice its cheapest piece for the only
+remaining Pawn. Mating potential is considered non-existent if the
+advantage in piece material is less than 350 cP ('one minor ahead'),
+the leading side has at most two pieces, and the defending side at
+most one (next to the Kings). The pair-bonus value can be used to
+flag some exceptional conditions that fine tune this, by indicating
+a 'minor' has mating potential, or minors that don't have mating
+potential even in pairs, or a piece is color bound, and thus cannot
+have mating potential on its own no matter how high its value.
+Finally a minor can be marked as 'tough defender', meaning it can
+hold out even against a Queen. As the Commoner is the only known
+case of this, it also implies mating potential.
+
+Without mating potential, a favorable score is divided by 8.
+If no mating potential will remain after sacrificing the last Pawn
+away, the score is divided by 4. In other cases having no Pawns
+will reduce your lead by a factor 2, except against a bare King
+(and perhaps some Pawns), where there is no discount.
+
+
+
H.G.Muller
projects / fairymax.git / commitdiff