Trait opencv::core::DownhillSolverConst

source · 
pub trait DownhillSolverConst: MinProblemSolverConst {
    fn as_raw_DownhillSolver(&self) -> *const c_void;

    fn get_init_step(&self, step: &mut dyn ToOutputArray) -> Result<()> { ... }
}
Expand description

This class is used to perform the non-linear non-constrained minimization of a function,

defined on an n-dimensional Euclidean space, using the Nelder-Mead method, also known as downhill simplex method. The basic idea about the method can be obtained from http://en.wikipedia.org/wiki/Nelder-Mead_method.

It should be noted, that this method, although deterministic, is rather a heuristic and therefore may converge to a local minima, not necessary a global one. It is iterative optimization technique, which at each step uses an information about the values of a function evaluated only at n+1 points, arranged as a simplex in n-dimensional space (hence the second name of the method). At each step new point is chosen to evaluate function at, obtained value is compared with previous ones and based on this information simplex changes it’s shape , slowly moving to the local minimum. Thus this method is using only function values to make decision, on contrary to, say, Nonlinear Conjugate Gradient method (which is also implemented in optim).

Algorithm stops when the number of function evaluations done exceeds termcrit.maxCount, when the function values at the vertices of simplex are within termcrit.epsilon range or simplex becomes so small that it can enclosed in a box with termcrit.epsilon sides, whatever comes first, for some defined by user positive integer termcrit.maxCount and positive non-integer termcrit.epsilon.

Note: DownhillSolver is a derivative of the abstract interface cv::MinProblemSolver, which in turn is derived from the Algorithm interface and is used to encapsulate the functionality, common to all non-linear optimization algorithms in the optim module.

Note: term criteria should meet following condition:

ⓘ
   termcrit.type == (TermCriteria::MAX_ITER + TermCriteria::EPS) && termcrit.epsilon > 0 && termcrit.maxCount > 0

Required Methods§

Provided Methods§

Returns the initial step that will be used in downhill simplex algorithm.

Parameters
  • step: Initial step that will be used in algorithm. Note, that although corresponding setter accepts column-vectors as well as row-vectors, this method will return a row-vector.
See also

DownhillSolver::setInitStep

Implementors§