Type Definition liblbfgs_sys::lbfgs_evaluate_t

pub type lbfgs_evaluate_t = Option<unsafe extern "C" fn(instance: *mut c_void, x: *const lbfgsfloatval_t, g: *mut lbfgsfloatval_t, n: c_int, step: lbfgsfloatval_t) -> lbfgsfloatval_t>;

Callback interface to provide objective function and gradient evaluations.

The lbfgs() function call this function to obtain the values of objective function and its gradients when needed. A client program must implement this function to evaluate the values of the objective function and its gradients, given current values of variables.

@param instance The user data sent for lbfgs() function by the client. @param x The current values of variables. @param g The gradient vector. The callback function must compute the gradient values for the current variables. @param n The number of variables. @param step The current step of the line search routine. @retval lbfgsfloatval_t The value of the objective function for the current variables.