272 lines
9.1 KiB
C++
272 lines
9.1 KiB
C++
/* ----------------------------------------------------------------------------
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* GTSAM Copyright 2010, Georgia Tech Research Corporation,
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* Atlanta, Georgia 30332-0415
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* All Rights Reserved
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* Authors: Frank Dellaert, et al. (see THANKS for the full author list)
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* See LICENSE for the license information
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* -------------------------------------------------------------------------- */
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/**
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* NonlinearOptimizer.h
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* @brief: Encapsulates nonlinear optimization state
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* @Author: Frank Dellaert
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* Created on: Sep 7, 2009
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*/
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#ifndef NONLINEAROPTIMIZER_H_
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#define NONLINEAROPTIMIZER_H_
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#include <boost/shared_ptr.hpp>
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#include <boost/make_shared.hpp>
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#include <gtsam/nonlinear/Ordering.h>
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#include <gtsam/linear/VectorValues.h>
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#include <gtsam/nonlinear/NonlinearFactorGraph.h>
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#include <gtsam/linear/Factorization.h>
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#include <gtsam/nonlinear/NonlinearOptimizationParameters.h>
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namespace gtsam {
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class NullOptimizerWriter {
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public:
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NullOptimizerWriter(double error) {}
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virtual void write(double error) {}
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};
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/**
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* The class NonlinearOptimizer encapsulates an optimization state.
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* Typically it is instantiated with a NonlinearFactorGraph and an initial config
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* and then one of the optimization routines is called. These recursively iterate
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* until convergence. All methods are functional and return a new state.
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*
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* The class is parameterized by the Graph type $G$, Values class type $T$,
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* linear system class $L$, the non linear solver type $S$, and the writer type $W$
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*
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* The values class type $T$ is in order to be able to optimize over non-vector values structures.
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*
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* A nonlinear system solver $S$
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* Concept NonLinearSolver<G,T,L> implements
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* linearize: G * T -> L
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* solve : L -> T
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*
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* The writer $W$ generates output to disk or the screen.
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*
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* For example, in a 2D case, $G$ can be Pose2Graph, $T$ can be Pose2Values,
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* $L$ can be GaussianFactorGraph and $S$ can be Factorization<Pose2Graph, Pose2Values>.
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* The solver class has two main functions: linearize and optimize. The first one
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* linearizes the nonlinear cost function around the current estimate, and the second
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* one optimizes the linearized system using various methods.
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*
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* To use the optimizer in code, include <gtsam/NonlinearOptimizer-inl.h> in your cpp file
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*
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*
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*/
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template<class G, class T, class L = GaussianFactorGraph, class S = Factorization<G, T>, class W = NullOptimizerWriter>
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class NonlinearOptimizer {
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public:
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// For performance reasons in recursion, we store configs in a shared_ptr
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typedef boost::shared_ptr<const T> shared_values;
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typedef boost::shared_ptr<const G> shared_graph;
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typedef boost::shared_ptr<const S> shared_solver;
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typedef const S solver;
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typedef NonlinearOptimizationParameters Parameters;
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private:
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// keep a reference to const version of the graph
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// These normally do not change
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const shared_graph graph_;
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// keep a values structure and its error
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// These typically change once per iteration (in a functional way)
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const shared_values config_;
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double error_; // TODO FD: no more const because in constructor I need to set it after checking :-(
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// keep current lambda for use within LM only
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// TODO: red flag, should we have an LM class ?
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const double lambda_;
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// the linear system solver
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const shared_solver solver_;
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// Recursively try to do tempered Gauss-Newton steps until we succeed
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NonlinearOptimizer try_lambda(const L& linear,
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Parameters::verbosityLevel verbosity, double factor, Parameters::LambdaMode lambdaMode) const;
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public:
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/**
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* Constructor that evaluates new error
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*/
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NonlinearOptimizer(shared_graph graph, shared_values config, shared_solver solver,
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const double lambda = 1e-5);
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/**
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* Constructor that does not do any computation
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*/
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NonlinearOptimizer(shared_graph graph, shared_values config, shared_solver solver,
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const double error, const double lambda): graph_(graph), config_(config),
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error_(error), lambda_(lambda), solver_(solver) {}
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/**
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* Copy constructor
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*/
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NonlinearOptimizer(const NonlinearOptimizer<G, T, L, S> &optimizer) :
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graph_(optimizer.graph_), config_(optimizer.config_),
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error_(optimizer.error_), lambda_(optimizer.lambda_), solver_(optimizer.solver_) {}
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/**
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* Return current error
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*/
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double error() const {
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return error_;
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}
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/**
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* Return current lambda
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*/
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double lambda() const {
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return lambda_;
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}
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/**
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* Return the config
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*/
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shared_values config() const{
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return config_;
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}
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/**
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* linearize and optimize
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* This returns an VectorValues, i.e., vectors in tangent space of T
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*/
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VectorValues linearizeAndOptimizeForDelta() const;
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/**
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* Do one Gauss-Newton iteration and return next state
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*/
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NonlinearOptimizer iterate(Parameters::verbosityLevel verbosity = Parameters::SILENT) const;
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/**
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* Optimize a solution for a non linear factor graph
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* @param relativeTreshold
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* @param absoluteTreshold
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* @param verbosity Integer specifying how much output to provide
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*/
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NonlinearOptimizer
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gaussNewton(double relativeThreshold, double absoluteThreshold,
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Parameters::verbosityLevel verbosity = Parameters::SILENT, int maxIterations = 100) const;
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/**
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* One iteration of Levenberg Marquardt
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*/
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NonlinearOptimizer iterateLM(Parameters::verbosityLevel verbosity = Parameters::SILENT,
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double lambdaFactor = 10, Parameters::LambdaMode lambdaMode = Parameters::BOUNDED) const;
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/**
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* Optimize using Levenberg-Marquardt. Really Levenberg's
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* algorithm at this moment, as we just add I*\lambda to Hessian
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* H'H. The probabilistic explanation is very simple: every
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* variable gets an extra Gaussian prior that biases staying at
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* current value, with variance 1/lambda. This is done very easily
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* (but perhaps wastefully) by adding a prior factor for each of
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* the variables, after linearization.
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*
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* @param relativeThreshold
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* @param absoluteThreshold
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* @param verbosity Integer specifying how much output to provide
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* @param lambdaFactor Factor by which to decrease/increase lambda
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*/
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NonlinearOptimizer
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levenbergMarquardt(double relativeThreshold, double absoluteThreshold,
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Parameters::verbosityLevel verbosity = Parameters::SILENT, int maxIterations = 100,
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double lambdaFactor = 10, Parameters::LambdaMode lambdaMode = Parameters::BOUNDED) const;
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NonlinearOptimizer
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levenbergMarquardt(const NonlinearOptimizationParameters ¶) const;
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/**
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* Static interface to LM optimization using default ordering and thresholds
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* @param graph Nonlinear factor graph to optimize
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* @param config Initial config
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* @param verbosity Integer specifying how much output to provide
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* @return an optimized values structure
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*/
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static shared_values optimizeLM(shared_graph graph, shared_values config,
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Parameters::verbosityLevel verbosity = Parameters::SILENT) {
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// Use a variable ordering from COLAMD
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Ordering::shared_ptr ordering = graph->orderingCOLAMD(*config);
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double relativeThreshold = 1e-5, absoluteThreshold = 1e-5;
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// initial optimization state is the same in both cases tested
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shared_solver solver(new S(ordering));
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NonlinearOptimizer optimizer(graph, config, solver);
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// Levenberg-Marquardt
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NonlinearOptimizer result = optimizer.levenbergMarquardt(relativeThreshold,
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absoluteThreshold, verbosity);
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return result.config();
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}
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/**
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* Static interface to LM optimization (no shared_ptr arguments) - see above
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*/
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inline static shared_values optimizeLM(const G& graph, const T& config,
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Parameters::verbosityLevel verbosity = Parameters::SILENT) {
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return optimizeLM(boost::make_shared<const G>(graph),
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boost::make_shared<const T>(config), verbosity);
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}
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/**
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* Static interface to GN optimization using default ordering and thresholds
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* @param graph Nonlinear factor graph to optimize
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* @param config Initial config
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* @param verbosity Integer specifying how much output to provide
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* @return an optimized values structure
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*/
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static shared_values optimizeGN(shared_graph graph, shared_values config,
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Parameters::verbosityLevel verbosity = Parameters::SILENT) {
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Ordering::shared_ptr ordering = graph->orderingCOLAMD(*config);
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double relativeThreshold = 1e-5, absoluteThreshold = 1e-5;
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// initial optimization state is the same in both cases tested
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shared_solver solver(new S(ordering));
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NonlinearOptimizer optimizer(graph, config, solver);
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// Gauss-Newton
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NonlinearOptimizer result = optimizer.gaussNewton(relativeThreshold,
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absoluteThreshold, verbosity);
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return result.config();
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}
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/**
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* Static interface to GN optimization (no shared_ptr arguments) - see above
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*/
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inline static shared_values optimizeGN(const G& graph, const T& config,
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Parameters::verbosityLevel verbosity = Parameters::SILENT) {
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return optimizeGN(boost::make_shared<const G>(graph),
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boost::make_shared<const T>(config), verbosity);
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}
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};
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/**
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* Check convergence
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*/
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bool check_convergence (
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double relativeErrorTreshold,
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double absoluteErrorTreshold,
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double errorThreshold,
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double currentError, double newError, int verbosity);
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} // gtsam
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#endif /* NONLINEAROPTIMIZER_H_ */
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