gtsam/cpp/NonlinearOptimizer-inl.h

/**
 * NonlinearOptimizer-inl.h
 * This is a template definition file, include it where needed (only!)
 * so that the appropriate code is generated and link errors avoided.
 * @brief: Encapsulates nonlinear optimization state
 * @Author: Frank Dellaert
 * Created on: Sep 7, 2009
 */

#pragma once

#include <iostream>
#include <boost/tuple/tuple.hpp>
#include "NonlinearOptimizer.h"

using namespace std;

namespace gtsam {

	/* ************************************************************************* */
	bool check_convergence(double relativeErrorTreshold,
			double absoluteErrorTreshold, double currentError, double newError,
			int verbosity) {
		// check if diverges
		double absoluteDecrease = currentError - newError;
		if (verbosity >= 2)
			cout << "absoluteDecrease: " << absoluteDecrease << endl;
		if (absoluteDecrease < 0)
			throw overflow_error(
					"NonlinearFactorGraph::optimize: error increased, diverges.");

		// calculate relative error decrease and update currentError
		double relativeDecrease = absoluteDecrease / currentError;
		if (verbosity >= 2)
			cout << "relativeDecrease: " << relativeDecrease << endl;
		bool converged = (relativeDecrease < relativeErrorTreshold)
				|| (absoluteDecrease < absoluteErrorTreshold);
		if (verbosity >= 1 && converged)
			cout << "converged" << endl;
		return converged;
	}

	/* ************************************************************************* */
	// Constructors
	/* ************************************************************************* */
	template<class G, class C>
	NonlinearOptimizer<G, C>::NonlinearOptimizer(const G& graph,
			const Ordering& ordering, shared_config config, double lambda) :
		graph_(&graph), ordering_(&ordering), config_(config), error_(graph.error(
				*config)), lambda_(lambda) {
	}

	/* ************************************************************************* */
	// linearize and optimize
	/* ************************************************************************* */
	template<class G, class C>
	VectorConfig NonlinearOptimizer<G, C>::linearizeAndOptimizeForDelta() const {

		// linearize the non-linear graph around the current config
		// which gives a linear optimization problem in the tangent space
		GaussianFactorGraph linear = graph_->linearize(*config_);

		// solve for the optimal displacement in the tangent space
		VectorConfig delta = linear.optimize(*ordering_);

		// return
		return delta;
	}

	/* ************************************************************************* */
	// One iteration of Gauss Newton
	/* ************************************************************************* */
	template<class G, class C>
	NonlinearOptimizer<G, C> NonlinearOptimizer<G, C>::iterate(
			verbosityLevel verbosity) const {

		// linearize and optimize
		VectorConfig delta = linearizeAndOptimizeForDelta();

		// maybe show output
		if (verbosity >= DELTA)
			delta.print("delta");

		// take old config and update it
		shared_config newConfig(new C(config_->exmap(delta)));

		// maybe show output
		if (verbosity >= CONFIG)
			newConfig->print("newConfig");

		return NonlinearOptimizer(*graph_, *ordering_, newConfig);
	}

	/* ************************************************************************* */
	template<class G, class C>
	NonlinearOptimizer<G, C> NonlinearOptimizer<G, C>::gaussNewton(
			double relativeThreshold, double absoluteThreshold,
			verbosityLevel verbosity, int maxIterations) const {
		// linearize, solve, update
		NonlinearOptimizer next = iterate(verbosity);

		// check convergence
		bool converged = gtsam::check_convergence(relativeThreshold,
				absoluteThreshold, error_, next.error_, verbosity);

		// return converged state or iterate
		if (converged)
			return next;
		else
			return next.gaussNewton(relativeThreshold, absoluteThreshold, verbosity);
	}

	/* ************************************************************************* */
	// Recursively try to do tempered Gauss-Newton steps until we succeed.
	// Form damped system with given lambda, and return a new, more optimistic
	// optimizer if error decreased or recurse with a larger lambda if not.
	// TODO: in theory we can't infinitely recurse, but maybe we should put a max.
	/* ************************************************************************* */
	template<class G, class C>
	NonlinearOptimizer<G, C> NonlinearOptimizer<G, C>::try_lambda(
			const GaussianFactorGraph& linear, verbosityLevel verbosity, double factor) const {

		if (verbosity >= TRYLAMBDA)
			cout << "trying lambda = " << lambda_ << endl;

		// add prior-factors
		GaussianFactorGraph damped = linear.add_priors(1.0/sqrt(lambda_));
		if (verbosity >= DAMPED)
			damped.print("damped");

		// solve
		VectorConfig delta = damped.optimize(*ordering_);
		if (verbosity >= TRYDELTA)
			delta.print("delta");

		// update config
		shared_config newConfig(new C(config_->exmap(delta)));
		if (verbosity >= TRYCONFIG)
			newConfig->print("config");

		// create new optimization state with more adventurous lambda
		NonlinearOptimizer next(*graph_, *ordering_, newConfig, lambda_ / factor);

		// if error decreased, return the new state
		if (next.error_ <= error_)
			return next;
		else {
			// TODO: can we avoid copying the config ?
			NonlinearOptimizer cautious(*graph_, *ordering_, config_, lambda_ * factor);
			return cautious.try_lambda(linear, verbosity, factor);
		}
	}

	/* ************************************************************************* */
	// One iteration of Levenberg Marquardt
	/* ************************************************************************* */
	template<class G, class C>
	NonlinearOptimizer<G, C> NonlinearOptimizer<G, C>::iterateLM(
			verbosityLevel verbosity, double lambdaFactor) const {

		// maybe show output
		if (verbosity >= CONFIG)
			config_->print("config");
		if (verbosity >= ERROR)
			cout << "error: " << error_ << endl;
		if (verbosity >= LAMBDA)
			cout << "lambda = " << lambda_ << endl;

		// linearize all factors once
		GaussianFactorGraph linear = graph_->linearize(*config_);
		if (verbosity >= LINEAR)
			linear.print("linear");

		// try lambda steps with successively larger lambda until we achieve descent
		return try_lambda(linear, verbosity, lambdaFactor);
	}

	/* ************************************************************************* */
	template<class G, class C>
	NonlinearOptimizer<G, C> NonlinearOptimizer<G, C>::levenbergMarquardt(
			double relativeThreshold, double absoluteThreshold,
			verbosityLevel verbosity, int maxIterations, double lambdaFactor) const {

		// do one iteration of LM
		NonlinearOptimizer next = iterateLM(verbosity, lambdaFactor);

		// check convergence
		// TODO: move convergence checks here and incorporate in verbosity levels
		// TODO: build into iterations somehow as an instance variable
		bool converged = gtsam::check_convergence(relativeThreshold,
				absoluteThreshold, error_, next.error_, verbosity);

		// return converged state or iterate
		if (converged || maxIterations <= 1) {
			// maybe show output
			if (verbosity >= CONFIG)
				next.config_->print("final config");
			if (verbosity >= ERROR)
				cout << "final error: " << next.error_ << endl;
			if (verbosity >= LAMBDA)
				cout << "final lambda = " << next.lambda_ << endl;
			return next;
		} else
			return next.levenbergMarquardt(relativeThreshold, absoluteThreshold,
					verbosity, lambdaFactor);
	}

/* ************************************************************************* */

}