Distance to King Formula - J-Value

[jhaglund]

Here's my program I made that could be helpful to some people. It calculates the distance to king, j-value, from an attacking square.

I used ICCF Numeric Chess Notation.


// test example
//83 - 21

//str[0] = 8;
//str[1] = 3;
//strk[0] = 2;
//strk[1] = 1;

//ga = 8
//gb = 3
//la = 2
//lb = 1

83-21 (h3 - b1) = 6.0408


Comments?

Joshua D. Haglund

/*
J-Value v1.0
by Joshua D. Haglund
January 16th 2010

Joshua-Value is the distance to king, in # of squares, from attacker piece.

Joshua was the king of kings.

*/

#include <stdio.h>
#include <string>
#include <iostream>

using namespace std;


int main()
{


cout << " " << endl;

string str;
string strk;

float jvalue;
float a,b,c;
float la,ga,lb,gb,va,vb;


cout << " Enter Square of Attacker Piece: ";
cin >> str;
cout << " Enter Square of Enemy King: ";
cin >> strk;

ga = str[0];
gb = str[1];

la = strk[0];
lb = strk[1];

a = gb - lb;
b = lb;
if(lb > gb)
a = lb - gb;
c = a / b;
va = ga - la;
vb = gb - lb;

if(ga < la)
va = la - ga;
if(ga > la)
va = ga - la;

if(gb < lb)
vb = lb - gb;
if(gb > lb)
vb = gb - lb;

if(va > 1 || vb >= 1)
jvalue = va;
if(vb > 1 || va >= 1)
jvalue = vb;
if(va > 1 || vb == 1)
jvalue = va;
if(va > 1 || vb == 0)
jvalue = va;
if(vb > 1 || va == 1)
jvalue = va;
if(vb > 1 || va == 0)
jvalue = vb;

if(va == 0 || vb > 0)
jvalue = vb;

if(va == 1 || vb > 1)
jvalue = vb+c;
if(vb == 1 || va > 1)
jvalue = va+c;

if(va == vb)
jvalue = va;
if(vb == va)
jvalue = vb;

if(va == 0)
jvalue = vb;
if(vb == 0)
jvalue = va;

cout.precision(5);
cout.width(5);
cout << " J-Value to King: " << jvalue << endl;

main();

system("pause");
return 0;
}

[jhaglund]

Bob, you should try this in Crafty...

Add a bonus based on distance to opposing king. It can be used for other pieces as well.

Smaller distance, = bigger bonus.

bonus[7] = {-7, -6, -5, -4, -3 ,-2 ,-1 , 0};
scale = 8 - jvalue;
if(alpha_bonus >= beta_bonus)
eval =+ bonus[scale]; // 8 squares - distance
return beta_bonus;
else
if(alpha_bonus <= beta_bonus)
eval =+ bonus[scale];
return alpha_bonus;

It can used to order moves, attacking the king & other pieces, & scoring for eval piece tables. Well you get the idea...

[vladstamate]

Hi,

I am confused. Why is the value 6.0408 and not 6? The squares distance between b1 and h3 is 6 squares.

Regards,
Vlad.

[jhaglund]

Hi,

I am confused. Why is the value 6.0408 and not 6? The squares distance between b1 and h3 is 6 squares.

Regards,
Vlad.

It's not on the same rank or file, making it a bit longer because you travel diagonally to the next rank. Think of it kinda like a^2 + b^2 = c^2 but counting in squares

abcdefgh
00000000 8
00000000 7
00000000 6
00000000 5
00000000 4
00000001 3
00000000 2
01000000 1

[jhaglund]

bonus[7] = {-7, -6, -5, -4, -3 ,-2 ,-1 , 0};

backwards....

more like:

bonus[7] = { 21, 18, 15, 12, 9, 6, 3, 0};

[vladstamate]

Hi Joshua,

It's not on the same rank or file, making it a bit longer because you travel diagonally to the next rank. Think of it kinda like a^2 + b^2 = c^2 but counting in squares

I understand now, thanks.

Regards,
Vlad.

[Kempelen]

Here's my program I made that could be helpful to some people. It calculates the distance to king, j-value, from an attacking square.

I used ICCF Numeric Chess Notation.


// test example
//83 - 21

//str[0] = 8;
//str[1] = 3;
//strk[0] = 2;
//strk[1] = 1;

//ga = 8
//gb = 3
//la = 2
//lb = 1

83-21 (h3 - b1) = 6.0408


Comments?

Joshua D. Haglund

Not sure, but maybe work with decimal numbers need more CPU time and could be counterproductive. Your idea need testing in order to know if it is worthy

[jhaglund]

Your idea need testing in order to know if it is worthy

I guess since no one else likes to take the initiative, I'll have to do this too...