optimization/test_functions/powell.m

   1 function f = powell(x1,x2,x3,x4)
   2   ## The Powell function. See Dennis & Schnabel, Appendix B, problem
   3   ## #1. (The "regular" Powell function is simply the Extended Powell
   4   ## with m=1).
   5   ##
   6   ## This function has a minimum at x=(0,0,0,0) with f(x) == 0. The
   7   ## suggested starting point is x0=(3,-1,0,1).
   8   ##
   9   f = (x1 + 10*x2)^2 + 5*(x3 - x4)^2;
  10   f = f + (x2 - 2*x3)^4 + 10*(x1 - x4)^4;
  11 end