Ri is the result of the game corresponding to position i; -1* for black win, 0 for draw and +1 for white win.

qi is corresponding to position i, the value returned by the chess engine evaluation function. (Computing the gradient on the QS is a waste of time - it is much faster to run the QS saving the PV and then compute the gradient using the evaluation function of the end-of-PV position - and not worry too much about the fact that tweaking the evaluation function could result in a different position being picked ^{[5]}).

Home * Automated Tuning * RuyTune## Table of Contents

RuyTune,an open source framework for tuning evaluation function parameters, written by Álvaro Begué in C++, released on Bitbucket

^{[1]}as introduced in November 2016^{[2]}. RuyTune is an instance of a logistic regression performing a limited-memory BFGS, a quasi-Newton method that approximates the Broyden–Fletcher–Goldfarb–Shanno algorithm with limited amount of memory. It uses thelibLBFGSlibrary^{[3]}along with reverse-mode automatic differentiation and requires that the evaluation function is converted to a C++ template function where the score type is a template parameter, and a database of quiescent positions with associated results^{[4]}.## Method

The function to minimize the mean squared error of the prediction is:where:

-1* for black win, 0 for draw and+1for white win.^{[5]}).^{[6]}.## See also

## Forum Posts

Re: Texel tuning method question by Álvaro Begué, CCC, June 07, 2017

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