I recently played someone on ICC and beat them, much to my delight, as
they were a lot stronger than me. I wanted to know what their rating
was before they played me, but could find no way of determining this.
I knew their rating after the game was 1682 and mine 1334, since
that's in the PGN file.

I've written a small program that computes this data. Given the
ratings AFTER a game finished (what's recorded in the PGN file), and
the result, the program can compute the ICC ratings of both yourself
and your opponent BEFORE the game started. (It only works for
established players, not those with provisional ratings. It only works
on ICC. I doubt FICS or anywhere else uses the exact same formula as
ICC).

It's a simple program - there is no graphical user interface. It
hardly needs it, as it just takes 3 numbers. Although ICC publish the
formula used in computing your new ratings given your old ratings,
there is no easy way to work this the other way around. I could not
re-arrange the equation. As such, the program does an exhaustive
search, trying all combinations of ratings between 800 and 3500 to see
what fits. It can take a bit of time to do this. It took 14 s on a 450
MHz Sun workstation, using players rated around 3450. It will take
less time for weaker players, as it does not need to do as much
seraching.

Here it is used, and as you can see my opponents rating before the
game was 1711 and mine 1305.

% iccratings 1334 1682 1
your old rating = 1305 Opponents old rating = 1711 Change = 29

I don't have a Windoze compiler, so can't produce a Windoze
executable, but I'm sure someone can do so. If anyone wants to send me
a version compiled for Windoze, I'll add it to the following zip file.
At present, the file only contains the C source code.

http://www.g8wrb.org/chess/iccratings.zip

(email me at

david
dot
kirkby // note the two k's in kirkby
at
onetel
dot
net

-------
% iccratings
iccratings - version 1.0 by Dr. D. Kirkby
Finds the ICC ratings before a game started, given
the final ICC ratings and the result
Licenced under the GNU Genenal Puplic Licence (GPL)

Usage: your_new_rating opponents_new_rating result
where result is 0, 0.5 or 1
and ratings are between 800 and 3500

ex 1: iccratings 1334 1682 1
ex 2: iccratings 1330 1686 0
ex 3: iccratings 1308 1200 0.5

This only works for 'established' players.

Hope this might be useful to someone. If I've wasted my time, let me
know, but flames to /dev/null. If anyone can find any cases where it
fails to work, let me know. I've not tested it extensively, but it
seems to be okay.


Dr. David Kirkby.

Can't you just check the other player's history? Just look at the game
played before yours by your opponent and your answer should be there. Be
sure to look at what kind of game was played before in the history, though
(blitz, bullet, standard, etc.) so you get an accurate answer.

"Dr. David Kirkby" m wrote
in message om...
I recently played someone on ICC and beat them, much to my delight, as
they were a lot stronger than me. I wanted to know what their rating
was before they played me, but could find no way of determining this.
I knew their rating after the game was 1682 and mine 1334, since
that's in the PGN file.

I've written a small program that computes this data. Given the
ratings AFTER a game finished (what's recorded in the PGN file), and
the result, the program can compute the ICC ratings of both yourself
and your opponent BEFORE the game started. (It only works for
established players, not those with provisional ratings. It only works
on ICC. I doubt FICS or anywhere else uses the exact same formula as
ICC).

It's a simple program - there is no graphical user interface. It
hardly needs it, as it just takes 3 numbers. Although ICC publish the
formula used in computing your new ratings given your old ratings,
there is no easy way to work this the other way around. I could not
re-arrange the equation. As such, the program does an exhaustive
search, trying all combinations of ratings between 800 and 3500 to see
what fits. It can take a bit of time to do this. It took 14 s on a 450
MHz Sun workstation, using players rated around 3450. It will take
less time for weaker players, as it does not need to do as much
seraching.

Here it is used, and as you can see my opponents rating before the
game was 1711 and mine 1305.

% iccratings 1334 1682 1
your old rating = 1305 Opponents old rating = 1711 Change = 29

I don't have a Windoze compiler, so can't produce a Windoze
executable, but I'm sure someone can do so. If anyone wants to send me
a version compiled for Windoze, I'll add it to the following zip file.
At present, the file only contains the C source code.

http://www.g8wrb.org/chess/iccratings.zip

(email me at

david
dot
kirkby // note the two k's in kirkby
at
onetel
dot
net

-------
% iccratings
iccratings - version 1.0 by Dr. D. Kirkby
Finds the ICC ratings before a game started, given
the final ICC ratings and the result
Licenced under the GNU Genenal Puplic Licence (GPL)

Usage: your_new_rating opponents_new_rating result
where result is 0, 0.5 or 1
and ratings are between 800 and 3500

ex 1: iccratings 1334 1682 1
ex 2: iccratings 1330 1686 0
ex 3: iccratings 1308 1200 0.5

This only works for 'established' players.

Hope this might be useful to someone. If I've wasted my time, let me
know, but flames to /dev/null. If anyone can find any cases where it
fails to work, let me know. I've not tested it extensively, but it
seems to be okay.


Dr. David Kirkby.

And the computer types wonder why they don't get dates. My God.

:-))
"buh bye" wrote in message
om...
And the computer types wonder why they don't get dates. My God.

ICC already have a command to do this.
I think it is 'assess' opponents handle.

Regards

"Dr. David Kirkby" m wrote
in message om...
I recently played someone on ICC and beat them, much to my delight, as
they were a lot stronger than me. I wanted to know what their rating
was before they played me, but could find no way of determining this.
I knew their rating after the game was 1682 and mine 1334, since
that's in the PGN file.

I've written a small program that computes this data. Given the
ratings AFTER a game finished (what's recorded in the PGN file), and
the result, the program can compute the ICC ratings of both yourself
and your opponent BEFORE the game started. (It only works for
established players, not those with provisional ratings. It only works
on ICC. I doubt FICS or anywhere else uses the exact same formula as
ICC).

It's a simple program - there is no graphical user interface. It
hardly needs it, as it just takes 3 numbers. Although ICC publish the
formula used in computing your new ratings given your old ratings,
there is no easy way to work this the other way around. I could not
re-arrange the equation. As such, the program does an exhaustive
search, trying all combinations of ratings between 800 and 3500 to see
what fits. It can take a bit of time to do this. It took 14 s on a 450
MHz Sun workstation, using players rated around 3450. It will take
less time for weaker players, as it does not need to do as much
seraching.

Here it is used, and as you can see my opponents rating before the
game was 1711 and mine 1305.

% iccratings 1334 1682 1
your old rating = 1305 Opponents old rating = 1711 Change = 29

I don't have a Windoze compiler, so can't produce a Windoze
executable, but I'm sure someone can do so. If anyone wants to send me
a version compiled for Windoze, I'll add it to the following zip file.
At present, the file only contains the C source code.

http://www.g8wrb.org/chess/iccratings.zip

(email me at

david
dot
kirkby // note the two k's in kirkby
at
onetel
dot
net

-------
% iccratings
iccratings - version 1.0 by Dr. D. Kirkby
Finds the ICC ratings before a game started, given
the final ICC ratings and the result
Licenced under the GNU Genenal Puplic Licence (GPL)

Usage: your_new_rating opponents_new_rating result
where result is 0, 0.5 or 1
and ratings are between 800 and 3500

ex 1: iccratings 1334 1682 1
ex 2: iccratings 1330 1686 0
ex 3: iccratings 1308 1200 0.5

This only works for 'established' players.

Hope this might be useful to someone. If I've wasted my time, let me
know, but flames to /dev/null. If anyone can find any cases where it
fails to work, let me know. I've not tested it extensively, but it
seems to be okay.


Dr. David Kirkby.

"garrubal" wrote in message news:Plkec.8096$HN3.211@fed1read07...
Can't you just check the other player's history? Just look at the game
played before yours by your opponent and your answer should be there. Be
sure to look at what kind of game was played before in the history, though
(blitz, bullet, standard, etc.) so you get an accurate answer.

Yes, if you do it quickly. I found my opponent had already played
another 20 games by the time I decided I wanted the information, so I
could not find it in his history. Obviously, if you know whilst
playing him/her, you can write it down. But if you want the
information some time later, I can find no way using tools on ICC to
get the information.

Five people have downloaded the C code from my web server. If any of
you can produce a binary for Windoze, let me have it. Perhaps, like
myself, you are not fans of Microsoft, and so intend using it on a
UNIX or Linux box.

Dr. David Kirkby

"Terry" wrote in message ...
ICC already have a command to do this.
I think it is 'assess' opponents handle.

Regards

No, the 'assess' command does the reverse of my program. The 'access'
allows you to determine what your rating will be if you win, loose or
drawn against an opponent. That's pretty easy to compute as the
formula is given on the ICC help pages at

http://chessclub.com/help/ratings

That's not the same as finding the rating of an opponent at the time
you played them. For that, there is no formula I'm aware of.

I don't see a way of doing what my program does using tools on ICC,
except by

a) Taking note of his rating before the game concluded OR
b) looking at the history if you do it before the opponent has played
20 games, and so you are still in their history.

I found I was out of my opponent's history. The history only extends
to 20 games, which includes all games. One could easily exhaust the
history file in under and hour if playing bullet. I did not check
until a couple of days later, after which my game could not be seen in
his history. Hence I put together the program, which took me an hour
or two.

I realise the program is not earth sattering and won't change chess
forever, but if it of any use to anyone, it is available for zero
cost.

Sorry, at this moment in time, I can only make the source available,
not a binary. I could produce a binary for Sun's Solaris, but I doubt
anyone would want that. But if anyone will make a windoze executable,
I'll add it to the zipfile.

Last time I looked, five people had downloaded the source code.

Dr. David Kirkby

"Dr. David Kirkby" m wrote
in message om...
"Terry" wrote in message
...
ICC already have a command to do this.
I think it is 'assess' opponents handle.

Regards

No, the 'assess' command does the reverse of my program. The 'access'
allows you to determine what your rating will be if you win, loose or
drawn against an opponent. That's pretty easy to compute as the
formula is given on the ICC help pages at

http://chessclub.com/help/ratings

That's not the same as finding the rating of an opponent at the time
you played them. For that, there is no formula I'm aware of.

I don't see a way of doing what my program does using tools on ICC,
except by

a) Taking note of his rating before the game concluded OR
b) looking at the history if you do it before the opponent has played
20 games, and so you are still in their history.

I found I was out of my opponent's history. The history only extends
to 20 games, which includes all games. One could easily exhaust the
history file in under and hour if playing bullet. I did not check
until a couple of days later, after which my game could not be seen in
his history. Hence I put together the program, which took me an hour
or two.

I realise the program is not earth sattering and won't change chess
forever, but if it of any use to anyone, it is available for zero
cost.

Sorry, at this moment in time, I can only make the source available,
not a binary. I could produce a binary for Sun's Solaris, but I doubt
anyone would want that. But if anyone will make a windoze executable,
I'll add it to the zipfile.

Last time I looked, five people had downloaded the source code.

Dr. David Kirkby

My mistake

Regards

I think this programme is worthless, since I don`t care about what it does.
But on the other hand, it probably didn`t take but a few minutes to write.
The average person watches over an hour of television every day. Who`s
wasting more time? Watched any TV lately, "buh bye"?


"buh bye" wrote in message
om...
And the computer types wonder why they don't get dates. My God.

Your program could be made *much* faster if you use the fact that the
maximum rating change after a game is 32.

Also, if you want to make the program more available I recommend
putting up a little webpage and doing the calculations in Javascript -
no compiling needed and anyone with a browser could use it.