
%%% outline
%-------------------------------------------------------------------------





    \begin{tikzpicture}
    \node [anchor=west,inner sep=2pt] (eq1) at (0,0) {$f(s_u|t_v)$};
    \node [anchor=west] (eq2) at (eq1.east) {$=$\ };
    \draw [-] ([xshift=0.3em]eq2.east) -- ([xshift=11.6em]eq2.east);
    \node [anchor=south west] (eq3) at ([xshift=1em]eq2.east) {$\sum_{k=1}^{K} c_{\mathbb{E}}(s_u|t_v;s^{[k]},t^{[k]})$};
    \node [anchor=north west] (eq4) at (eq2.east) {$\sum_{s'_u} \sum_{k=1}^{K} c_{\mathbb{E}}(s'_u|t_v;s^{[k]},t^{[k]})$};

   {
    \node [anchor=south] (label1) at ([yshift=-6em,xshift=3em]eq1.north west) {利用这个公式计算};
    \node [anchor=north west] (label1part2) at ([yshift=0.3em]label1.south west) {新的$f(s_u|t_v)$值};
    }
    {
    \node [anchor=west] (label2) at ([xshift=5em]label1.east) {用当前的$f(s_u|t_v)$};
    \node [anchor=north west] (label2part2) at ([yshift=0.3em]label2.south west) {计算期望频次$c_{\mathbb{E}}(\cdot)$};
    }

    {
    \node [anchor=west,fill=red!20,inner sep=2pt] (eq1) at (0,0) {$f(s_u|t_v)$};
    }

    \begin{pgfonlayer}{background}
    {
    \node[rectangle,fill=blue!20,inner sep=0] [fit = (eq3) (eq4)] (c) {};
    }
   {
    \node[rectangle,draw,red,inner sep=0] [fit = (label1) (label1part2)] (flabel) {};
    }
    {
    \node[rectangle,draw,ublue,inner sep=0] [fit = (label2) (label2part2)] (clabel) {};
    }
    \end{pgfonlayer}

    {
    \draw [->,thick] (eq1.south) ..controls +(south:1.5em) and +(north:1.5em).. (flabel.north);
    }
    {
    \draw [->,thick] (c.south) ..controls +(south:1.0em) and +(north:1.0em).. (clabel.north);
    }

    {
    \draw [->,thick] ([yshift=1em]flabel.east) -- ([yshift=1em]clabel.west);
    \draw [<-,thick] ([yshift=-1em]flabel.east) -- ([yshift=-1em]clabel.west) node [pos=0.5,above,yshift=0.3em] {\footnotesize{{反复执行}}};
    }
    \end{tikzpicture}




