Some statistics about promotions and underpromotions.

[sje]

Likewise, there is no special marking for an en passant capture, or any kind of a drawing move.

[xmas79]

EP moves are quite easy to detect:

black captures are always a pawn push in 4th rank followed by capture in 3rd rank in the same file. The same principle is for white:

Code: Select all

([abcdefgh])[4][ ]+[abcdefgh]x\1[3]    <--- black ep capture
([abcdefgh])[5][ ]+(\d+)\.[ ]+[abcdefgh]x\1[6] <--- white ep capture

Notice white ep capture is slightly different as there is the move number in between.

edit:
more compact version:

Code: Select all

([abcdefgh])4[ ]+[abcdefgh]x\13    <--- black ep capture
([abcdefgh])5[ ]+\d+\.[ ]+[abcdefgh]x\16 <--- white ep capture

[sje]

Won't work. There may be a capture of a different pawn on the same target rank but not file.

[xmas79]

What? How? Still talking about chess? No ep capture... but if the file is the same then it is an ep capture.

[xmas79]

Actually the problem is that this will tirgger false captures:

Code: Select all

([abcdefgh])4[ ]+[abcdefgh]x\13    <--- black ep capture 
([abcdefgh])5[ ]+\d+\.[ ]+[abcdefgh]x\16 <--- white ep capture 

eg: 4.Ng4 fxg3
eg: 4.h3 Ng5 5.fxg6

Solution is to ensure that the first move is actually a pawn move, so no piece or letter or number before destination square:

Code: Select all

\.[ ]*([abcdefgh])4[ ]+[abcdefgh]x\13    <--- black ep capture 
[ ]+([abcdefgh])5[ ]+\d+\.[ ]+[abcdefgh]x\16 <--- white ep capture

[sje]

What? How? Still talking about chess? No ep capture... but if the file is the same then it is an ep capture.

[d]
Ba6 Bb5+ Bc4 Bd3 Be2 Ke2 Na3 Nc3 Ne2 Nf3 Nh3 Qe2 Qf3 Qg4 Qh5+ a3 a4 b3 b4 c3 c4 d3 d4 e6 exd6 exf6 f3 f4 g3 g4 h3 h4

[xmas79]

What? How? Still talking about chess? No ep capture... but if the file is the same then it is an ep capture.

[d]
Ba6 Bb5+ Bc4 Bd3 Be2 Ke2 Na3 Nc3 Ne2 Nf3 Nh3 Qe2 Qf3 Qg4 Qh5+ a3 a4 b3 b4 c3 c4 d3 d4 e6 exd6 exf6 f3 f4 g3 g4 h3 h4

What? I repeat: a pawn push followed by a capture in the same file one rank "before". That is:

1.e4 a5 2.e5 d5 3.exd6

This is what my regex does.

[sje]

Please show your regex as a grep call. Also, what about the case where the moves are separated by a newline?

[xmas79]

Code: Select all

natale@ubuntu-develop:~$ echo -e "1.e4 h5 2.e5\n\n\n d5 3.   exd6 Nf6 \n \n \n 4.f4\n Ne4 5.f5 g5 6.fxg6 Nf6 7.b4 h4 8.b5 a6 9.Nf3 c5 10.bxa6" | sed ':a;N;$!ba;s/\n/ /g' | egrep -oh "([a-h])5[ ]+[0-9]+\.[ ]*[a-h]x\16" | wc -l
2

natale@ubuntu-develop:~$ echo -e "1.e4 h5 2.e5\n\n\n d5 3.   exd6 Nf6 \n \n \n 4.f4\n Ne4 5.f5 g5 6.fxg6 Nf6 7.b4 h4 8.b5 a6 9.Nf3 c5 10.bxa6" | sed ':a;N;$!ba;s/\n/ /g' | egrep -oh "([a-h])5[ ]+[0-9]+\.[ ]*[a-h]x\16"
d5 3.exd6
g5 6.fxg6

natale@ubuntu-develop:~$ echo -e "1.e4 h5 2.e5\n\n\n d5 3.   exd6 Nf6 \n \n \n 4.f4\n Ne4 5.f5 g5 6.fxg6 Nf6 7.b4 h4 8.b5 a6 9.Nf3 c5 10.bxc6" | sed ':a;N;$!ba;s/\n/ /g' | egrep -oh "([a-h])5[ ]+[0-9]+\.[ ]*[a-h]x\16" | wc -l
3

natale@ubuntu-develop:~$ echo -e "1.e4 h5 2.e5\n\n\n d5 3.   exd6 Nf6 \n \n \n 4.f4\n Ne4 5.f5 g5 6.fxg6 Nf6 7.b4 h4 8.b5 a6 9.Nf3 c5 10.bxc6" | sed ':a;N;$!ba;s/\n/ /g' | egrep -oh "([a-h])5[ ]+[0-9]+\.[ ]*[a-h]x\16"
d5 3.exd6
g5 6.fxg6
c5 10.bxc6

[sje]

After a certain point, command line operations for scanning a PGN file searching for certain moves or conditions become too ornate for practical use. Really, a database is needed for this.

For promotions in general, I am reminded of a chess variant seen from long ago where a player could promote a pawn only to a piece which had already been captured. The idea was to remove the need for having extra queens (or whatever) in the physical chess set. It is interesting to ponder how a chess program's search would have to be modified to adapt to this rule.

Today, many of the chess sets for sale (like the Mark of Westminster sets offered by Our Sponsor) have an extra pair of queens included. This practice was unheard of back in Old Days when I never had more than US$5 to spend on a set.