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Uri Blass
Joined: 08 Mar 2006
Posts: 6012
Location: Tel-Aviv Israel
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 Posted: Mon May 21, 2007 10:17 am Post subject: fen to fen functions |
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I wonder if there is a free program with source that finds symmetric positions of a specific position.
The program simply should get a fen and parameter (same side to move in case that there is no problem because of castling rights or different side to move) and return a symmetric fen
Example:
The program should get the following fen
[D]4k3/8/8/pppppppp/8/8/PPPPPPPP/4K3 w - - 0 1
it can return the following fens(when the first is for the same side to move and the second is for different side to move)
[D]3k4/8/8/pppppppp/8/8/PPPPPPPP/3K4 w - - 0 1
[D]4k3/pppppppp/8/8/PPPPPPPP/8/8/4K3 b - - 0 1 |
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Alessandro Scotti
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| Posted: Mon May 21, 2007 3:20 pm Post subject: Re: fen to fen functions |
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| There is some code in Kiwi that does something very similar to what you need, it's in engine.cxx function runEvalSuiteEPD. |
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Reinhard Scharnagl
Joined: 13 Mar 2006
Posts: 468
Location: Munich, Germany
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| Posted: Mon May 21, 2007 5:10 pm Post subject: Re: fen to fen functions |
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Hi Uri,
SMIRF has such an edit option, but its source is not free. It changes
[D]4k3/8/8/pppppppp/8/8/PPPPPPPP/4K3 w - - 0 1
to
[D]4k3/pppppppp/8/8/PPPPPPPP/8/8/4K3 b - - 0 1
And this "switch positions" is working also for Chess960 and 10x8 CRC.
Regards, Reinhard. |
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Dann Corbit
Joined: 08 Mar 2006
Posts: 5125
Location: Redmond, WA USA
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| Posted: Mon May 21, 2007 5:48 pm Post subject: Re: fen to fen functions |
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| Uri Blass wrote: |
I wonder if there is a free program with source that finds symmetric positions of a specific position.
The program simply should get a fen and parameter (same side to move in case that there is no problem because of castling rights or different side to move) and return a symmetric fen
Example:
The program should get the following fen
[D]4k3/8/8/pppppppp/8/8/PPPPPPPP/4K3 w - - 0 1
it can return the following fens(when the first is for the same side to move and the second is for different side to move)
[D]3k4/8/8/pppppppp/8/8/PPPPPPPP/3K4 w - - 0 1
[D]4k3/pppppppp/8/8/PPPPPPPP/8/8/4K3 b - - 0 1 |
There is a visual basic utility written by Les Fernandez that does exactly that.
I can send you a copy if you want, including the source code. |
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Uri Blass
Joined: 08 Mar 2006
Posts: 6012
Location: Tel-Aviv Israel
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| Posted: Tue May 22, 2007 1:21 pm Post subject: Re: fen to fen functions |
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| smrf wrote: |
Hi Uri,
SMIRF has such an edit option, but its source is not free. It changes
[D]4k3/8/8/pppppppp/8/8/PPPPPPPP/4K3 w - - 0 1
to
[D]4k3/pppppppp/8/8/PPPPPPPP/8/8/4K3 b - - 0 1
And this "switch positions" is working also for Chess960 and 10x8 CRC.
Regards, Reinhard. |
Note that the function that I asked about is not function that is dependent on the move generator and the same function may be useful for many engines.
It is not an hard task to do it and I will write in C a function that does it by myself.
Uri |
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Alessandro Scotti
Guest
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| Posted: Tue May 22, 2007 3:46 pm Post subject: Re: fen to fen functions |
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Just a wild shot:
| Code: |
void fen2fen( char * fen, char * buf )
{
for( char * e = strchr(fen,' ') - 1; e >= fen; e-- ) {
*buf++ = *e ^ (isalpha(*e) ? 0x20 : 0x00);
}
strcpy( buf, strchr(fen,' ') );
}
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Uri Blass
Joined: 08 Mar 2006
Posts: 6012
Location: Tel-Aviv Israel
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| Posted: Tue May 22, 2007 4:24 pm Post subject: Re: fen to fen functions |
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| Alessandro Scotti wrote: |
Just a wild shot:
| Code: |
void fen2fen( char * fen, char * buf )
{
for( char * e = strchr(fen,' ') - 1; e >= fen; e-- ) {
*buf++ = *e ^ (isalpha(*e) ? 0x20 : 0x00);
}
strcpy( buf, strchr(fen,' ') );
}
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If I understand correctly you try both to replace the side to move and replace the files of the pieces so a1 goes to h8 in this code.
This code also does not replace the side to move that is part of the fen
and it also is not correct for castling because there are order rules
and you need to write KQkq in this order and kqKQ is not correct fen.
This code is clearly shorter than my code.
I did not know the trick of xoring with 0x20 to make big letters small letters and the opposite.
I wrote so far code only for the case of changing side that is always possible and not for the case of left-right symmetry that may be impossible in case of castling rights(unless you use FRC and not normal chess and in that case left-right symmetry is always possible)
I did not go from the end to the beginning of the string and simply saved an array of strings for every rank of the board when later I used strncat to make from them one string(I have a special function to change one line when I do not need to change the order but only change big letters to small letters and the opposite).
I did not check that your code works but
thanks for sharing your code
I can make my code shorter based on the idea that you gave here but I do not think that it is important.
Uri |
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Alessandro Scotti
Guest
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| Posted: Tue May 22, 2007 4:46 pm Post subject: Re: fen to fen functions |
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Hi Uri,
yes my code only tries to address the easiest scenario and it simply copies anything that follows the board representation. After all I'm not H. G. and there is a limit to what I can do in four lines of code! 
I think we could run an informal contest for the:
1) shortest code (but clean and elegant);
2) shortest and trickiest code (anything goes).
Anyone interested? |
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Dann Corbit
Joined: 08 Mar 2006
Posts: 5125
Location: Redmond, WA USA
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| Posted: Tue May 22, 2007 6:33 pm Post subject: Re: fen to fen functions |
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| Uri Blass wrote: |
| Alessandro Scotti wrote: |
Just a wild shot:
| Code: |
void fen2fen( char * fen, char * buf )
{
for( char * e = strchr(fen,' ') - 1; e >= fen; e-- ) {
*buf++ = *e ^ (isalpha(*e) ? 0x20 : 0x00);
}
strcpy( buf, strchr(fen,' ') );
}
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If I understand correctly you try both to replace the side to move and replace the files of the pieces so a1 goes to h8 in this code.
This code also does not replace the side to move that is part of the fen
and it also is not correct for castling because there are order rules
and you need to write KQkq in this order and kqKQ is not correct fen.
This code is clearly shorter than my code.
I did not know the trick of xoring with 0x20 to make big letters small letters and the opposite.
I wrote so far code only for the case of changing side that is always possible and not for the case of left-right symmetry that may be impossible in case of castling rights(unless you use FRC and not normal chess and in that case left-right symmetry is always possible)
I did not go from the end to the beginning of the string and simply saved an array of strings for every rank of the board when later I used strncat to make from them one string(I have a special function to change one line when I do not need to change the order but only change big letters to small letters and the opposite).
I did not check that your code works but
thanks for sharing your code
I can make my code shorter based on the idea that you gave here but I do not think that it is important.
Uri |
The xor trick relies upon the ASCII character set where 'A' is 0x41 and 'a' is 0x61 up to 'Z' is 0x5A and 'z' is 0x7A.
You can make reversing case more plain with:
foo = isupper(foo) ? tolower(foo) : toupper(foo);
Note that the toupper() and tolower() macros/functions do nothing if the input integer is not an alphabetic letter. |
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Uri Blass
Joined: 08 Mar 2006
Posts: 6012
Location: Tel-Aviv Israel
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| Posted: Thu May 24, 2007 12:52 pm Post subject: Re: fen to fen functions |
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| Alessandro Scotti wrote: |
Hi Uri,
yes my code only tries to address the easiest scenario and it simply copies anything that follows the board representation. After all I'm not H. G. and there is a limit to what I can do in four lines of code!
I think we could run an informal contest for the:
1) shortest code (but clean and elegant);
2) shortest and trickiest code (anything goes).
Anyone interested? |
No chance in competition
I simply tries to write code that works and I am not a good programmer like you but here is my code.
Note that it does not translate move to make in epd files but only the string of the position
Note that I used your trick of xoring with 0x20 to go from small letters to big letters and the opposite otherwise my code could be longer.
I have a different function to check if the string is legal fen so this certainly can crash on illegal fen.
| Code: |
char fen1[1024];
char shortfen[10];
char * opp_line(char *rankfen)
{
strcpy(shortfen,rankfen);
unsigned int i;
for (i=0;i<strlen(shortfen);i++)
// if (shortfen[i]>='a'&&shortfen[i]<='z')
// shortfen[i]+='A'-'a';
// else
// if (shortfen[i]>='A'&&shortfen[i]<='Z')
// shortfen[i]+='a'-'A';
if (isalpha(shortfen[i]))
shortfen[i]^=0x20;
return shortfen;
}
char *tranpose_line(char *rankfen)
{
memset(shortfen,0,10);
for( char * e = rankfen+strlen(rankfen) - 1; e >= rankfen; e-- )
shortfen[strlen(shortfen)]=*e;
return shortfen;
}
enum {shortcastlewhite=1,longcastlewhite=2,shortcastleblack=4,longcastleblack=8};
char * translate_fen_1(char *fen)
{
memset(fen1,0,1024);
char tempfen[10];
char tempfen2[10][10];
unsigned int l=strlen(fen);
unsigned int i=0;
int i0;
int j=0;
int cast=0;
while ((i<l)&&(fen[i]==' '))
i++;
while (fen[i]!=' ')
{
i0=i;
while ((fen[i]!='/')&&(fen[i]!=' '))
i++;
memset(tempfen,0,10);
memcpy(tempfen,fen+i0,i-i0+1);
strcpy(tempfen2[j],opp_line(tempfen));
if (fen[i]=='/')
i++;
j++;
}
j--;
strncat(fen1,tempfen2[j],strlen(tempfen2[j]));
fen1[strlen(fen1)-1]='/';
while (j>0)
{
j--;
strncat(fen1,tempfen2[j],strlen(tempfen2[j]));
}
fen1[strlen(fen1)-1]=' ';
i++;
while (fen[i]==' ')
i++;
if ((fen[i]=='w')||(fen[i]=='W'))
fen1[strlen(fen1)]='b';
else
fen1[strlen(fen1)]='w';
fen1[strlen(fen1)]=' ';
i++;
while (fen[i]==' ')
i++;
if (fen[i]=='-')
{
fen1[strlen(fen1)]='-';
i++;
}
else
{
while (fen[i]!=' ')
{
if (fen[i]=='k')
cast|=shortcastlewhite;
if (fen[i]=='q')
cast|=longcastlewhite;
if (fen[i]=='K')
cast|=shortcastleblack;
if (fen[i]=='Q')
cast|=longcastleblack;
i++;
}
if (cast&shortcastlewhite)
fen1[strlen(fen1)]='K';
if (cast&longcastlewhite)
fen1[strlen(fen1)]='Q';
if (cast&shortcastleblack)
fen1[strlen(fen1)]='k';
if (cast&longcastleblack)
fen1[strlen(fen1)]='q';
}
fen1[strlen(fen1)]=' ';
while (fen[i]==' ')
i++;
if (fen[i]=='-')
fen1[strlen(fen1)]='-';
else
{
fen1[strlen(fen1)]=fen[i];
i++;
fen1[strlen(fen1)]=9-fen[i];
}
i++;
while (i!=l)
{
fen1[strlen(fen1)]=fen[i];
i++;
}
return fen1;
}
char *translate_fen_2(char *fen)
{
unsigned int l=strlen(fen);
unsigned int i=0;
char tempfen[10];
int i0;
int cast=0;
memset(fen1,0,1024);
while ((i<l)&&(fen[i]==' '))
i++;
while (fen[i]!=' ')
{
i0=i;
while ((fen[i]!='/')&&(fen[i]!=' '))
i++;
memset(tempfen,0,10);
memcpy(tempfen,fen+i0,i-i0);
strcat(fen1,tranpose_line(tempfen));
fen1[strlen(fen1)]=fen[i];
if (fen[i]=='/')
i++;
}
while ((fen[i]==' ')&&(i<l))
i++;
//correct color
if (i<l)
fen1[strlen(fen1)]=fen[i];
//correct space after color
fen1[strlen(fen1)]=' ';
i++;
if (fen[i]==' ')
i++;
if (i<l)
if (fen[i]=='-')
{
while (i<l)
{
fen1[strlen(fen1)]=fen[i];
i++;
}
}
else
{
//castling rights
while ((fen[i]!=' ')&&(i<l))
{
if (fen[i]=='k')
cast|=longcastleblack;
if (fen[i]=='q')
cast|=shortcastleblack;
if (fen[i]=='K')
cast|=longcastlewhite;
if (fen[i]=='Q')
cast|=shortcastlewhite;
i++;
}
if (cast&shortcastlewhite)
fen1[strlen(fen1)]='K';
if (cast&longcastlewhite)
fen1[strlen(fen1)]='Q';
if (cast&shortcastleblack)
fen1[strlen(fen1)]='k';
if (cast&longcastleblack)
fen1[strlen(fen1)]='q';
while (i<l)
{
fen1[strlen(fen1)]=fen[i];
i++;
}
}
return fen1;
} |
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