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Diffstat (limited to 'extern/ceres/internal/ceres/cgnr_linear_operator.h')
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diff --git a/extern/ceres/internal/ceres/cgnr_linear_operator.h b/extern/ceres/internal/ceres/cgnr_linear_operator.h new file mode 100644 index 00000000000..44c07cabd01 --- /dev/null +++ b/extern/ceres/internal/ceres/cgnr_linear_operator.h @@ -0,0 +1,120 @@ +// Ceres Solver - A fast non-linear least squares minimizer +// Copyright 2015 Google Inc. All rights reserved. +// http://ceres-solver.org/ +// +// Redistribution and use in source and binary forms, with or without +// modification, are permitted provided that the following conditions are met: +// +// * Redistributions of source code must retain the above copyright notice, +// this list of conditions and the following disclaimer. +// * Redistributions in binary form must reproduce the above copyright notice, +// this list of conditions and the following disclaimer in the documentation +// and/or other materials provided with the distribution. +// * Neither the name of Google Inc. nor the names of its contributors may be +// used to endorse or promote products derived from this software without +// specific prior written permission. +// +// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" +// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE +// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR +// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF +// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS +// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN +// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) +// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE +// POSSIBILITY OF SUCH DAMAGE. +// +// Author: keir@google.com (Keir Mierle) + +#ifndef CERES_INTERNAL_CGNR_LINEAR_OPERATOR_H_ +#define CERES_INTERNAL_CGNR_LINEAR_OPERATOR_H_ + +#include <algorithm> +#include "ceres/linear_operator.h" +#include "ceres/internal/scoped_ptr.h" +#include "ceres/internal/eigen.h" + +namespace ceres { +namespace internal { + +class SparseMatrix; + +// A linear operator which takes a matrix A and a diagonal vector D and +// performs products of the form +// +// (A^T A + D^T D)x +// +// This is used to implement iterative general sparse linear solving with +// conjugate gradients, where A is the Jacobian and D is a regularizing +// parameter. A brief proof that D^T D is the correct regularizer: +// +// Given a regularized least squares problem: +// +// min ||Ax - b||^2 + ||Dx||^2 +// x +// +// First expand into matrix notation: +// +// (Ax - b)^T (Ax - b) + xD^TDx +// +// Then multiply out to get: +// +// = xA^TAx - 2b^T Ax + b^Tb + xD^TDx +// +// Take the derivative: +// +// 0 = 2A^TAx - 2A^T b + 2 D^TDx +// 0 = A^TAx - A^T b + D^TDx +// 0 = (A^TA + D^TD)x - A^T b +// +// Thus, the symmetric system we need to solve for CGNR is +// +// Sx = z +// +// with S = A^TA + D^TD +// and z = A^T b +// +// Note: This class is not thread safe, since it uses some temporary storage. +class CgnrLinearOperator : public LinearOperator { + public: + CgnrLinearOperator(const LinearOperator& A, const double *D) + : A_(A), D_(D), z_(new double[A.num_rows()]) { + } + virtual ~CgnrLinearOperator() {} + + virtual void RightMultiply(const double* x, double* y) const { + std::fill(z_.get(), z_.get() + A_.num_rows(), 0.0); + + // z = Ax + A_.RightMultiply(x, z_.get()); + + // y = y + Atz + A_.LeftMultiply(z_.get(), y); + + // y = y + DtDx + if (D_ != NULL) { + int n = A_.num_cols(); + VectorRef(y, n).array() += ConstVectorRef(D_, n).array().square() * + ConstVectorRef(x, n).array(); + } + } + + virtual void LeftMultiply(const double* x, double* y) const { + RightMultiply(x, y); + } + + virtual int num_rows() const { return A_.num_cols(); } + virtual int num_cols() const { return A_.num_cols(); } + + private: + const LinearOperator& A_; + const double* D_; + scoped_array<double> z_; +}; + +} // namespace internal +} // namespace ceres + +#endif // CERES_INTERNAL_CGNR_LINEAR_OPERATOR_H_ |