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      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 (at) google.com (Sameer Agarwal)
     30 //         keir (at) 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 
     44 namespace ceres {
     45 
     46 class LossFunction;
     47 
     48 namespace internal {
     49 
     50 class 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.
     65 class 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