A Representation for the Target Function

Our approximation of $V$ is given by $\hat{V}$: \[ \hat{V}(b) = w_{0} + w_{1}\cdot bp(b) + w_{2}\cdot rp(b) + w_{3}\cdot bk(b) + w_{4}\cdot rk(b) + w_{5}\cdot bt(b) + w_{6}\cdot rt(b) \]
$bp(b)$: number of black pieces on board $b$.
$rp(b)$: number of red pieces on $b$.
$bk(b)$: number of black kings on $b$.
$rk(b)$: number of red kings on $b$.
$bt(b)$: number of red pieces threatened by black (i.e., which can be taken on black's next turn).
$rt(b)$: number of black pieces threatened by red.