function varargout = minimize_args(fn, length, varargin)
%MINIMIZE_ARGS use Carl Rasmussen's MINIMIZE on multiple array variables
%
% [x1, x2, ..., fn_value, i] = optimize_args(fn, length, varargin)
%
% This calls Carl Rasmussen's minimize, but allows minimizing
% functions with the following signature:
%   [f_value, df_dx1, ... df_dxK] = fn(x1, ..., xK)
% fn's arguments can be nd-arrays, not just vectors. All the dirty wrapping and
% unwrapping of parameters in and out of vectors is done for you.
%
% Inputs:
%             fn   @fn   Function to optimize
%         length   1x1   Number of fn evals (if +ve) / line searches (if -ve)
%                        See Carl's code for more information
%       varargin arglist Initial conditions for variables
%
% Outputs:
%     varargout  ?x? [opt_x1, opt_x2, ..., opt_xK, opt_fn_value, i]
%                    (as in Carl's code, "i" is # fn evals or line searches)

% Iain Murray, November 2007, July 2008

[wrap, unwrap] = arg_wrappers(varargin{:});
init = wrap(varargin{:});
min_fn = @(x) cost_grad_fn(x, fn, wrap, unwrap);

[X, fX, i] = minimize(init, min_fn, length);

minimum = unwrap(X);
varargout = {minimum{:}, fX, i};


function [fx, dfx] = cost_grad_fn(x, fn, wrap, unwrap)

args = unwrap(x);
out = cell(length(args) + 1, 1);
[out{:}] = fn(args{:});
fx = out{1};
dfx = wrap(out{2:end});