本文从直觉上说明ktt条件成立的正确性。
1. KKT条件
考虑优化问题:
m i n f ( x ) s . t h k ( x ) = 0 , g j ( x ) ≤ 0 ; k = 1 , 2 , . . . n , j = 1 , . . l ; minf(x) \\ s.t \quad h_{k}(x)=0,g_{j}(x)\leq0;k=1,2,...n,j=1,..l; minf(x)s.thk(x)=0,gj(x)≤0;k=1,2,...n,j=1,..l;
KTT条件:如果x*是上述问题的最优解,则满足下面的必要条件
{ ∇ f ( x ∗ ) + ∑ k α k ∇ h k ( x ) + ∑ j β j ∇ g j ( x ∗ ) = 0 ( 1 ) β j ≥ 0 ( 2 ) β j g j ( x ∗ ) = 0 ( 3 ) g j ( x ∗ ) ≤ 0 ( 4 ) \left\{ \begin{aligned} \nabla f(x^*)+\sum _k \alpha_k \nabla h_{k}(x)+\sum_j \beta_{j}\nabla g_{j}(x^*)=0 \quad (1) \\ \beta_{j} \geq0 \quad (2)\\ \beta_{j}g_{j}(x^*) = 0 \quad (3) \\ g_{j}(x^*) \leq 0 \quad (4) \\ \end{aligned} \right. ⎩⎪⎪⎪⎪⎪⎪⎨⎪⎪⎪⎪⎪⎪⎧∇f