Wednesday, August 23, 2017

RELO proposal by Harri Hurme

On the MatPlus forum, Harri Hurme makes a great proposal for RELO, an improved Elo system for solvers of chess problems.
As Piotr Murdzia keeps on losing rating points, even if he wins all tournaments, the old system needs an overhaul indeed. So anyone interested should read Harri Hurme's idea.

The most relevant parts of the posting are quoted below.

 We can calculate the first cornerstone in the rating system, which is the difficulty rating for the problems, using the old ratings of solvers and the solving results as the basis. We call this rating as "Rdifficulty", this tells how tough an "opponent" each problem is.

Rdifficulty = Rav-C*arctanh(2*Pav/Pmax-1);
where Rav = average rating for solvers who have old rating
C=800/ln(10) = 347.4
Pav =average points for each problem by solvers who have old rating
Pmax=maximum points for a problem (presently Pmax=5)

I prefer using inverse of hyperbolic tanget but I could use logistic function as well.


After calculating the difficulty of the problems we can proceed with standard Elo rating methods. I give the required formulas though here as well.

Pexpected = 0.5(1+tanh((Ro-Rdifficulty)/C)

This is calculated separately for each solver and each problem and summed. The new Rating

Rnew= Ro+K*sum(Pachieved-Pexpected);

The coefficient K is normally 4 but can be different as in normal Elo-rating calculations, (4*Pmax=20). The K factor can be different for different category solving tourneys. Also the number of solvers should affect it. These questions need practical testing and thus this should be discussed after testing.

Calculate performance rating for each (new) solver. At this point we know the “opponents” (each problem) ratings and results ratings

Rperformance=Rav+C*(arctanh(2*Pt/Pmaxt-1)-arctanh(2*Pavt/Pmaxt-1))

The index t means that here total summed points are in use, not per problem as above.

The classical Elo rating is based on cumulative normal distribution.
Instead of the normal distribution prof Arpad Elo suggest to use so called logistic function as an approximation of the distribution. The basic reason for the approximation seems to be ability to carry practical calculations readily. However the logistic function 1/(1+10 (Ro-Ropp)/ 400) ) is a close approximation. Actually US chess federation consider this as more accurate. We transform the logistic function into more practical form by using hyperbolic tangent function and its inverse with the following mathematical identity: Logistic function 1/(1+10^x) = 0.5*(1+tanh(x/2)).
The hyperbolic tangent function is commonly used in engineering because its approximation evaluation is very simple, with small argument values
Tanh(x) ~ x and tanh(x)=1, if X>> 1 and tanh(x)=-1 if x<<-1. This helps in approximating in the normal middle range.

Saturday, August 19, 2017

Did Kasparov destroy his own legend? An opinion piece.

The Rapid and Blitz in St. Louis is over, and we have seen that Kasparov still belongs to the top players of the world - in the top 20 to top 30 in any case, possibly even in the top 10 - but he is not the eight-eyed monster that sees everything anymore. He is not the Linares winner of 2005 anymore. He is not the world champion anymore. Kasparov has demontaged his own legend, he has become a mortal, an aging chess master over his zenith. He still is a great player, and for many having the strength that Kasparov showed in St. Louis is a target they can only dream of, but he now is one of many, not even a primus inter parem, far less the number one.

The world champion who played David Braben's Elite in his free time has matured into a political activist for whom chess has become a hobby, just like Elite back then. Maybe it is time to train hard, to have the greatest comeback in chess history. Or maybe it is time to just enjoy chess, play some tourneys for fun, win some opens, retire from politics and enjoy life.

Or maybe it is time for something new. Who knows what is Garry's next invention? The video game loving boy of the 1980s soon ventured into chess software and hardware, having an own series of chess computers. Will the mature Kasparov use his influence once more to find ways to improve chess for the general public? Now he is a politician, and countries that teach chess in schools have proven it to be successful for the social development of children. And in fact Kasparov already worked towards chess in schools. Why not again?

Garry, you might not be the best anymore. But you are still a legend. Use it for the best!

Sunday, August 13, 2017

Development of a Sabra Tourney helpmate

The 20th Sabra Tourney called for the opening and closing of a line by a black piece. I have come up with a simple idea, and after sending it to Paz Einat, I found that I can have two variations with a small change, so I also sent him the new position.

Siegfried Hornecker
Original for 20th Sabra Tourney
(Original publication)
Helpmate in 2, 2 solutions

1.Bd5 Qh7 2.0-0-0 Qc7 mate
1.Bd3 Qh1 2.0-0-0 Q:b7 mate
This small idea has the flaw of Black castling both times to the same side, and Paz decided to work on it. After an earlier unthematic version, he presented a final result, which he sent as original to the judge.


Paz Einat & Siegfried Hornecker
20th Sabra Tourney 2017, 4th prize
Helpmate in 2
a) Diagram above
b) Diagram below

a) 1.S4g5 R:h4 2.0-0 B:h7 mate
b) 1.S4c5 B:f3 2.0-0-0 B:b7 mate

Pinning the white queen prevented many unwanted solutions, but there is unfortunately a lot of material necessary to ensure the correctness. However, the helpmate shows both castlings, and this was pretty difficult to develop. So of course the bottle of Sabra we won went to Paz, as he did most of the work! But - hopefully we will see it in the FIDE Album! And what better celebration of the friendship of our countries Israel and Germany?


Addendum, 14 August 2017: The complete award is now available on the Variantim website:
http://www.variantim.org/20th%20Sabra%20Tourney%20award.pdf