\addtolength{\tabcolsep}{-4pt}

\begin{tabular}{c c c}

\begin{tikzpicture}
\begin{scope}
% ,minimum height =1em,minimum width=2em
\tikzstyle{model} = [draw,black,very thick,inner sep=3.5pt,rounded corners=4pt,fill=blue!20,minimum width=4em,minimum height=1.5em,font=\footnotesize]
\tikzstyle{data} = [draw,black,very thick,inner sep=3.5pt,rounded corners=4pt,fill=green!20,minimum width=4em,minimum height=1.5em,font=\footnotesize]
\tikzstyle{word} = [inner sep=3.5pt,font=\footnotesize]

\node[data] (old) at (0,0) {旧数据};
\node[data] (new) at ([xshift=3em]old.east) {新数据};
\node[data] (all) at ([xshift=2.55em,yshift=-4em]old.south) {最终数据};
\node[model] (final_model) at ([xshift=0em,yshift=-4em]all.south) {最终模型};

\draw [->,thick] ([yshift=-0.2em]old.south) .. controls +(south:2.5em) and +(north:2.5em) .. ([xshift=-0.2em,yshift=0.2em]all.north);
\draw [->,thick] ([yshift=-0.2em]new.south) .. controls +(south:2.5em) and +(north:2.5em) .. ([xshift=0.2em,yshift=0.2em]all.north);
\draw [->,thick] ([yshift=-0.2em]all.south) -- ([yshift=0.2em]final_model.north)node[pos=0.5,right,align=center,font=\footnotesize] {训练};

\node[word] at ([yshift=-2em]final_model.south){（a）数据混合};

\end{scope}
\end{tikzpicture}
&
\begin{tikzpicture}
\begin{scope}
\tikzstyle{model} = [draw,black,very thick,inner sep=3.5pt,rounded corners=4pt,fill=blue!20,minimum width=4em,minimum height=1.5em,font=\footnotesize]
\tikzstyle{data} = [draw,black,very thick,inner sep=3.5pt,rounded corners=4pt,fill=green!20,minimum width=4em,minimum height=1.5em,font=\footnotesize]
\tikzstyle{word} = [inner sep=3.5pt,font=\footnotesize]

\node[data] (old) at (0,0) {旧数据};
\node[data] (new) at ([xshift=3em]old.east) {新数据};
\node[model] (old_model) at ([yshift=-4em]old.south) {旧模型};
\node[model] (new_model) at ([yshift=-4em]new.south) {新模型};

\node[model] (final_model) at ([xshift=2.55em,yshift=-4em]old_model.south) {最终模型};

\draw [->,thick] ([yshift=-0.2em]old.south) -- ([yshift=0.2em]old_model.north) node[pos=0.5,left,align=center,font=\footnotesize] {训练};
\draw [->,thick] ([yshift=-0.2em]new.south) -- ([yshift=0.2em]new_model.north) node[pos=0.5,right,align=center,font=\footnotesize] {训练};
\draw [->,thick] ([yshift=-0.2em]old_model.south) .. controls +(south:2.5em) and +(north:2.5em) .. ([xshift=-0.2em,yshift=0.2em]final_model.north);
\draw [->,thick] ([yshift=-0.2em]new_model.south) .. controls +(south:2.5em) and +(north:2.5em) .. ([xshift=0.2em,yshift=0.2em]final_model.north);

\node[word] at ([yshift=2em]final_model.north) {插值};


\node[word] at ([yshift=-2em]final_model.south){（b）模型插值};

%空白占位
\node[word] at ([xshift=-3em]old.west) {};
\node[word] at ([xshift=3em]new.east) {};

\end{scope}
\end{tikzpicture}
&
\begin{tikzpicture}
\begin{scope}
\tikzstyle{model} = [draw,black,very thick,inner sep=3.5pt,rounded corners=4pt,fill=blue!20,minimum width=4em,minimum height=1.5em,font=\footnotesize]
\tikzstyle{data} = [draw,black,very thick,inner sep=3.5pt,rounded corners=4pt,fill=green!20,minimum width=4em,minimum height=1.5em,font=\footnotesize]
\tikzstyle{word} = [inner sep=3.5pt,font=\footnotesize]

\node[data] (old) at (0,0) {旧数据};
\node[data] (new) at ([xshift=3em]old.east) {新数据};
\node[model] (final_model) at ([yshift=-8.8em]new.south) {最终模型};

\draw [->,thick] ([yshift=-0.2em]new.south) -- ([xshift=0.2em,yshift=0.2em]final_model.north) node[pos=0.5,right,align=center,font=\footnotesize] {目标\\函数1};
\draw [->,thick,dashed] ([yshift=-0.2em]old.south) .. controls +(south:4.5em) and +(north:4.5em) .. ([xshift=-0.2em,yshift=0.2em]final_model.north) node[align=center,font=\footnotesize] at ([xshift=-0.1em,yshift=-4em]old.south) {目标\\函数2};

\node[word] at ([yshift=-2em,xshift=-2.55em]final_model.south){（c）多目标训练};

\end{scope}
\end{tikzpicture}

\end{tabular}

\addtolength{\tabcolsep}{4pt}