function g = powell_gradient(x1,x2,x3,x4)
- ##
- ## The gradient of the Powell function. See powell.m for more
- ## information.
- ##
+ %
+ % The gradient of the Powell function. See powell.m for more
+ % information.
+ %
f_x1 = 40*(x1 - x4)^3 + 2*x1 + 20*x2;
f_x2 = 4*(x2 - 2*x3)^3 + 20*x1 + 200*x2;
f_x3 = -8*(x2 - 2*x3)^3 + 10*x3 - 10*x4;