你确定这个超模是这么定义的？ 上面那个f()经过简单计算可知左边恒等于右边。超模如果对应的是"supermodular" .其定义是这样的：If f has increasing differences in (xn;xm), for every n ≠ m, then the function f is supermodular。 The function f:ℜ2→ℜ has increasing differences if for all x′′>x′, the difference
f(x′′,θ)–f(x′,θ) is nondecreasing in θ.
For the simplest case, only consider the function f(x,θ), then supermodular is equivalent to increasing difference, which means fxθ greater or equal to zero (complementarity), thus we car derive the result that as theta increase, x-star increase as well.

感觉大概理解了，结合上面两个，就是一个投入元素的增加，会引致其他（另一个）投入元素的回报（结果变化）增加，这就是超模。
举个例子，比如我办公室一个同事的收入增加了，我跟着也会因他请客而又更多免费的饭吃，我的回报也变好了，因为我们是朋友，也就是我们两个具有互补性。