residual_block.h revision 0ae28bd5885b5daa526898fcf7c323dc2c3e1963 
1// Ceres Solver - A fast non-linear least squares minimizer
2// Copyright 2010, 2011, 2012 Google Inc. All rights reserved.
3// http://code.google.com/p/ceres-solver/
4//
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16//
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28//
29// Author: sameeragarwal@google.com (Sameer Agarwal)
30//         keir@google.com (Keir Mierle)
31//
32// Purpose : Class and struct definitions for parameter and residual blocks.
33
34#ifndef CERES_INTERNAL_RESIDUAL_BLOCK_H_
35#define CERES_INTERNAL_RESIDUAL_BLOCK_H_
36
37#include <vector>
38
39#include "ceres/cost_function.h"
40#include "ceres/internal/port.h"
41#include "ceres/internal/scoped_ptr.h"
42#include "ceres/types.h"
43
44namespace ceres {
45
46class LossFunction;
47
48namespace internal {
49
50class ParameterBlock;
51
52// A term in the least squares problem. The mathematical form of each term in
53// the overall least-squares cost function is:
54//
55//    1
56//   --- loss_function( || cost_function(block1, block2, ...) ||^2  ),
57//    2
58//
59// Storing the cost function and the loss function separately permits optimizing
60// the problem with standard non-linear least techniques, without requiring a
61// more general non-linear solver.
62//
63// The residual block stores pointers to but does not own the cost functions,
64// loss functions, and parameter blocks.
65class ResidualBlock {
66 public:
67  ResidualBlock(const CostFunction* cost_function,
68                const LossFunction* loss_function,
69                const vector<ParameterBlock*>& parameter_blocks);
70
71  // Evaluates the residual term, storing the scalar cost in *cost, the residual
72  // components in *residuals, and the jacobians between the parameters and
73  // residuals in jacobians[i], in row-major order. If residuals is NULL, the
74  // residuals are not computed. If jacobians is NULL, no jacobians are
75  // computed. If jacobians[i] is NULL, then the jacobian for that parameter is
76  // not computed.
77  //
78  // Evaluate needs scratch space which must be supplied by the caller via
79  // scratch. The array should have at least NumScratchDoublesForEvaluate()
80  // space available.
81  //
82  // The return value indicates the success or failure. If the function returns
83  // false, the caller should expect the the output memory locations to have
84  // been modified.
85  //
86  // The returned cost and jacobians have had robustification and local
87  // parameterizations applied already; for example, the jacobian for a
88  // 4-dimensional quaternion parameter using the "QuaternionParameterization"
89  // is num_residuals by 3 instead of num_residuals by 4.
90  bool Evaluate(double* cost,
91                double* residuals,
92                double** jacobians,
93                double* scratch) const;
94
95  const CostFunction* cost_function() const { return cost_function_; }
96  const LossFunction* loss_function() const { return loss_function_; }
97
98  // Access the parameter blocks for this residual. The array has size
99  // NumParameterBlocks().
100  ParameterBlock* const* parameter_blocks() const {
101    return parameter_blocks_.get();
102  }
103
104  // Number of variable blocks that this residual term depends on.
105  int NumParameterBlocks() const {
106    return cost_function_->parameter_block_sizes().size();
107  }
108
109  // The size of the residual vector returned by this residual function.
110  int NumResiduals() const { return cost_function_->num_residuals(); }
111
112  // The minimum amount of scratch space needed to pass to Evaluate().
113  int NumScratchDoublesForEvaluate() const;
114
115 private:
116  const CostFunction* cost_function_;
117  const LossFunction* loss_function_;
118  scoped_array<ParameterBlock*> parameter_blocks_;
119};
120
121}  // namespace internal
122}  // namespace ceres
123
124#endif  // CERES_INTERNAL_RESIDUAL_BLOCK_H_
125