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 //
5 // Redistribution and use in source and binary forms, with or without
6 // modification, are permitted provided that the following conditions are met:
7 //
8 // * Redistributions of source code must retain the above copyright notice,
9 //   this list of conditions and the following disclaimer.
10 // * Redistributions in binary form must reproduce the above copyright notice,
11 //   this list of conditions and the following disclaimer in the documentation
12 //   and/or other materials provided with the distribution.
13 // * Neither the name of Google Inc. nor the names of its contributors may be
14 //   used to endorse or promote products derived from this software without
15 //   specific prior written permission.
16 //
17 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
18 // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 // ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
21 // LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
22 // CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
23 // SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
24 // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
25 // CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
26 // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
27 // POSSIBILITY OF SUCH DAMAGE.
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 <string>
38 #include <vector>
39 
40 #include "ceres/cost_function.h"
41 #include "ceres/internal/port.h"
42 #include "ceres/internal/scoped_ptr.h"
43 #include "ceres/stringprintf.h"
44 #include "ceres/types.h"
45 
46 namespace ceres {
47 
48 class LossFunction;
49 
50 namespace internal {
51 
52 class ParameterBlock;
53 
54 // A term in the least squares problem. The mathematical form of each term in
55 // the overall least-squares cost function is:
56 //
57 //    1
58 //   --- loss_function( || cost_function(block1, block2, ...) ||^2  ),
59 //    2
60 //
61 // Storing the cost function and the loss function separately permits optimizing
62 // the problem with standard non-linear least techniques, without requiring a
63 // more general non-linear solver.
64 //
65 // The residual block stores pointers to but does not own the cost functions,
66 // loss functions, and parameter blocks.
67 class ResidualBlock {
68  public:
69   // Construct the residual block with the given cost/loss functions. Loss may
70   // be null. The index is the index of the residual block in the Program's
71   // residual_blocks array.
72   ResidualBlock(const CostFunction* cost_function,
73                 const LossFunction* loss_function,
74                 const vector<ParameterBlock*>& parameter_blocks,
75                 int index);
76 
77   // Evaluates the residual term, storing the scalar cost in *cost, the residual
78   // components in *residuals, and the jacobians between the parameters and
79   // residuals in jacobians[i], in row-major order. If residuals is NULL, the
80   // residuals are not computed. If jacobians is NULL, no jacobians are
81   // computed. If jacobians[i] is NULL, then the jacobian for that parameter is
82   // not computed.
83   //
84   // Evaluate needs scratch space which must be supplied by the caller via
85   // scratch. The array should have at least NumScratchDoublesForEvaluate()
86   // space available.
87   //
88   // The return value indicates the success or failure. If the function returns
89   // false, the caller should expect the the output memory locations to have
90   // been modified.
91   //
92   // The returned cost and jacobians have had robustification and local
93   // parameterizations applied already; for example, the jacobian for a
94   // 4-dimensional quaternion parameter using the "QuaternionParameterization"
95   // is num_residuals by 3 instead of num_residuals by 4.
96   //
97   // apply_loss_function as the name implies allows the user to switch
98   // the application of the loss function on and off.
99   bool Evaluate(bool apply_loss_function,
100                 double* cost,
101                 double* residuals,
102                 double** jacobians,
103                 double* scratch) const;
104 
105 
cost_function()106   const CostFunction* cost_function() const { return cost_function_; }
loss_function()107   const LossFunction* loss_function() const { return loss_function_; }
108 
109   // Access the parameter blocks for this residual. The array has size
110   // NumParameterBlocks().
parameter_blocks()111   ParameterBlock* const* parameter_blocks() const {
112     return parameter_blocks_.get();
113   }
114 
115   // Number of variable blocks that this residual term depends on.
NumParameterBlocks()116   int NumParameterBlocks() const {
117     return cost_function_->parameter_block_sizes().size();
118   }
119 
120   // The size of the residual vector returned by this residual function.
NumResiduals()121   int NumResiduals() const { return cost_function_->num_residuals(); }
122 
123   // The minimum amount of scratch space needed to pass to Evaluate().
124   int NumScratchDoublesForEvaluate() const;
125 
126   // This residual block's index in an array.
index()127   int index() const { return index_; }
set_index(int index)128   void set_index(int index) { index_ = index; }
129 
ToString()130   string ToString() {
131     return StringPrintf("{residual block; index=%d}", index_);
132   }
133 
134  private:
135   const CostFunction* cost_function_;
136   const LossFunction* loss_function_;
137   scoped_array<ParameterBlock*> parameter_blocks_;
138 
139   // The index of the residual, typically in a Program. This is only to permit
140   // switching from a ResidualBlock* to an index in the Program's array, needed
141   // to do efficient removals.
142   int32 index_;
143 };
144 
145 }  // namespace internal
146 }  // namespace ceres
147 
148 #endif  // CERES_INTERNAL_RESIDUAL_BLOCK_H_
149