Rosenbrock function

The Rosenbrock function, often referred to as the Rosenbrock's valley or Rosenbrock's banana function, is a non-convex function used as a performance test problem for optimization algorithms. It is defined in two dimensions as: \[ f(x, y) = (a - x)^2 + b(y - x^2)^2 \] where \(a\) and \(b\) are constants.