The optimized function represented by a structure with the following fields:

• dims dimensinoality of the objective function.
• fun name of M-file that evaluates the objective function.
• gradfun name of M-file that evaluates the gradient. default ''
• gradeps used by finite difference method, in case gradfun was not supplied. default 1e-3

It should be set before the call to cv.ConjGradSolver.minimize, as default value is not usable.