Micro-Max, 一个短小精干的棋类引擎（仅133行 ）

变量索引表 Variable Index

为了最小化 micro-Max的源代码的字符数，所有字符均采用1个字符变量名，这使得变量名无意义，无描述（这坑了多少童鞋啊） In order to minimize the number of characters in the source code of micro-Max,
all variables have one-character names, which makes the names rather non-descriptive.
The following list with descriptions might therefore be helpful.
Some names are used for different variables in main() and D().
A letter D or m in the second column of the table distinguishes the case. A space there indicates that this is a global (‘static’) variable. Most global variables are used to pass information from one instance of the recursive search routine D() to the next, or between that routine and the main program. To be visible to the routine that uses them, the corresponding names can then not be used for a local variables. This makes that we have nearly run out of one-letter names for use in D().

In the list below variables used in micro-Max 3.2 or 4.0 are printed in blue. Variables that are already reserved for future enhancements are given in orange.

Lower Case

a D *_ Pointer to hash-table entry for current position
b char[] Chess board as 0x88 array, invalid squares contain piece-square table
c D
m char[] In ‘main()’ this is the input buffer
d D int Loop counter of iterative deepening, indicates depth
e D int Argument to pass current (differentially updated) evaluation
f D char Origin square of threat move
g D char Target square of threat move
h D int Temporay, used to calculate new remaining ply depth
i D int Temporay, used to hold some evaluation terms
j D int Loop counter for loop over directions
m int General loop counter. In Max 4 seed to hash key #2
k D int Argument to indicate side to move (8=white, 16=black)
m int In ‘main()’ it also holds the side to move
l D int Argument to pass upper window limit (beta)
m D int Value of best move so far
n char[] ASCII representation of pieces on board printout
D int Argument to pass current (differentially updated) evaluation
o char[] list of move vectors, index into this list, and initial-setup array
p D char Type of piece doing the move under consideration
m *char in ‘main()’ it is a pointer into the input buffer
q D int Argument to pass lower window limit (alpha)
r D int Step vector of current ray in move generation
s D
t D char Piece to be captured by move under consideration
u D char Piece doing the move under consideration
v D int Temporay, used to hold some evaluation terms
w char[] Relative value of pieces (Pawn = 1)
x D char Origin square of move under consideration
y D char Target square of move under consideration
z D int Argument to pass target square of previous move

Upper Case

A _[] Hash table B D char Start square of board scan for move generation C int Constant 799 for conversion ASCII -> square number, approx. value queen D int() Recursive search routine
E D int Argument to pass e.p. flag F
F D int e.p. flag: square skipped over in double move of P or K
G D int Corner square for castling, contains S = 0x80 on non-castling
H D char Capture square, where captured piece stands
I int Constant 8000 = ‘infinity’ score
J D int Argument to pass hash key #1
K int Origin square of input move
L int Target square of input move
M int Constant 0x88 = unused bits in valid square numbers
N int Counter of searched nodes, for timing purposes
O char Passes e.p. flag to next move at game level
P D int Value of null move
Q int Passes differentially updated evaluation score to next move
R char Origin square of best move returned by ‘D()’
S int Constant 0x80 = 128-bit (sign bit of char)
T char[] Random numbers for hash key, really int, but packed as char
U MACRO
V int Constant 0x70 = rank mask of 0x88 board
W char Target square of best move returned by ‘D()’
X D char Origin square of best move so far
Y D char Target square of best move so far, marked with 128-bit as non-castling
Z D int Argument to pass hash key #2
_ struct Name of structure for hash-table entry

Macro Definitions

F Shorthand for for( ; ; )
K Access to packed random-number table T[piece][square] for hash key
J Differential update of hash key
W Shorthand for while( )
U Hash table size

Structure Field Names

_.D char Depth
_.K int Hash Lock
_.V int Value of position
_.X char Move origin square, 8- and 128-bit encode score type (upper/lower bound)
_.Y char Move target square, 128-bit indicates non-castling