From 40c8a6b427486601a70e7c82d475cd9948eae619 Mon Sep 17 00:00:00 2001 From: H.G. Muller Date: Tue, 12 Feb 2013 21:11:01 +0100 Subject: [PATCH] Update README file --- README | 32 +++++++++++++++++++++++++++++++- 1 files changed, 31 insertions(+), 1 deletions(-) diff --git a/README b/README index 6dadac8..ef8be00 100644 --- a/README +++ b/README @@ -1,6 +1,9 @@ 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): @@ -26,5 +29,32 @@ you can include the argument 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 -- 1.7.0.4