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yap-6.3/packages/yap-lbfgs/ex1.pl
2013-06-13 17:57:55 -05:00

54 lines
1.7 KiB
Prolog

%%% -*- Mode: Prolog; -*-
% This file is part of YAP-LBFGS.
% Copyright (C) 2009 Bernd Gutmann
%
% YAP-LBFGS is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
%
% YAP-LBFGS is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with YAP-LBFGS. If not, see <http://www.gnu.org/licenses/>.
:- use_module(library(lbfgs)).
% This is the call back function which evaluates F and the gradient of F
evaluate(FX,_N,_Step) :-
optimizer_get_x(0,X0),
FX is sin(X0),
G0 is cos(X0),
optimizer_set_g(0,G0).
% This is the call back function which is invoked to report the progress
% if the last argument is set to anywhting else than 0, the optimizer will
% stop right now
progress(FX,X_Norm,G_Norm,Step,_N,Iteration,Ls,0) :-
optimizer_get_x(0,X0),
format('~d. Iteration : x0=~4f f(X)=~4f |X|=~4f |X\'|=~4f Step=~4f Ls=~4f~n',[Iteration,X0,FX,X_Norm,G_Norm,Step,Ls]).
demo :-
format('Optimizing the function f(x0) = sin(x0)~n',[]),
optimizer_initialize(1,evaluate,progress),
StartX is random*10,
format('We start the search at the random position x0=~5f~2n',[StartX]),
optimizer_set_x(0,StartX),
optimizer_run(BestF,Status),
optimizer_get_x(0,BestX0),
optimizer_finalize,
format('~2nOptimization done~nWe found a minimum at f(~f)=~f~2nLBFGS Status=~w~n',[BestX0,BestF,Status]).