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). 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):

sudo make install

This will install the executables in /usr/games, (where XBoard expects
them), and their data files in /usr/share/games/fairymax.

Should you want to compile by hand, you could use the following 
commands:

gcc -O2 fairymax.c -o fairymax

gcc -O2 fairymax.c -DSHATRANJ -o shamax

gcc -O2 maxqi.c -o maxqi

In this case you will get versions that expect their fmax.ini or qmax.ini
files in the current direcory. To change the default path of the ini files,
you can include the argument 

-DINI_FILE=\"pathname\"

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