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Commit b6e274bd authored by Davis King's avatar Davis King
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Filled out the svm_rank_trainer's spec

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dlib/svm/svm_rank_trainer.h
View file @ b6e274bd
...@@ -375,6 +375,13 @@ namespace dlib ...@@ -375,6 +375,13 @@ namespace dlib
return df; return df;
} }
const decision_function<kernel_type> train (
const ranking_pair<sample_type>& sample
) const
{
return train(std::vector<ranking_pair<sample_type> >(1, sample));
}
private: private:
scalar_type C; scalar_type C;
...@@ -388,5 +395,6 @@ namespace dlib ...@@ -388,5 +395,6 @@ namespace dlib
// ---------------------------------------------------------------------------------------- // ----------------------------------------------------------------------------------------
} }
#endif // DLIB_SVM_RANK_TrAINER_H__ #endif // DLIB_SVM_RANK_TrAINER_H__
dlib/svm/svm_rank_trainer_abstract.h
View file @ b6e274bd
// Copyright (C) 2012 Davis E. King (davis@dlib.net)
// License: Boost Software License See LICENSE.txt for the full license.
#undef DLIB_SVM_RANK_TrAINER_ABSTRACT_H__
#ifdef DLIB_SVM_RANK_TrAINER_ABSTRACT_H__
#include "ranking_tools_abstract.h"
#include "sparse_vector_abstract.h"
#include "function_abstract.h"
#include "kernel_abstract.h"
#include "../algs.h"
namespace dlib
{
// ----------------------------------------------------------------------------------------
template <
typename K
>
class svm_rank_trainer
{
/*!
REQUIREMENTS ON K
Is either linear_kernel or sparse_linear_kernel.
WHAT THIS OBJECT REPRESENTS
This object represents a tool for training a ranking support vector machine
using linear kernels. In particular, this object is a tool for training
the Ranking SVM described in the paper:
Optimizing Search Engines using Clickthrough Data by Thorsten Joachims
Note that we normalize the C parameter by multiplying it by 1/(number of ranking pairs).
Therefore, to make an exact comparison between this object and Equation 12
in the paper you must multiply C by the appropriate normalizing quantity.
Finally, note that the implementation of this object is done using the oca
optimizer and count_ranking_inversions() method. This means that it runs
in O(n*log(n)) time, making it suitable for use with large datasets.
!*/
public:
typedef K kernel_type;
typedef typename kernel_type::scalar_type scalar_type;
typedef typename kernel_type::sample_type sample_type;
typedef typename kernel_type::mem_manager_type mem_manager_type;
typedef decision_function<kernel_type> trained_function_type;
svm_rank_trainer (
);
/*!
ensures
- This object is properly initialized and ready to be used to train a
ranking support vector machine.
- #get_oca() == oca() (i.e. an instance of oca with default parameters)
- #get_c() == 1
- #get_epsilon() == 0.001
- this object will not be verbose unless be_verbose() is called
- #get_max_iterations() == 10000
- #learns_nonnegative_weights() == false
!*/
explicit svm_rank_trainer (
const scalar_type& C
);
/*!
requires
- C > 0
ensures
- This object is properly initialized and ready to be used to train a
ranking support vector machine.
- #get_oca() == oca() (i.e. an instance of oca with default parameters)
- #get_c() == C
- #get_epsilon() == 0.001
- this object will not be verbose unless be_verbose() is called
- #get_max_iterations() == 10000
- #learns_nonnegative_weights() == false
!*/
void set_epsilon (
scalar_type eps
);
/*!
requires
- eps > 0
ensures
- #get_epsilon() == eps
!*/
const scalar_type get_epsilon (
);
/*!
ensures
- returns the error epsilon that determines when training should stop.
Smaller values may result in a more accurate solution but take longer to
train. You can think of this epsilon value as saying "solve the
optimization problem until the average ranking accuracy is within epsilon
of its optimal value". Here we mean "ranking accuracy" in the same sense
used by test_ranking_function() and cross_validate_multiclass_trainer().
!*/
unsigned long get_max_iterations (
) const;
/*!
ensures
- returns the maximum number of iterations the SVM optimizer is allowed to
run before it is required to stop and return a result.
!*/
void set_max_iterations (
unsigned long max_iter
);
/*!
ensures
- #get_max_iterations() == max_iter
!*/
void be_verbose (
);
/*!
ensures
- This object will print status messages to standard out so that a user can
observe the progress of the algorithm.
!*/
void be_quiet (
);
/*!
ensures
- this object will not print anything to standard out
!*/
void set_oca (
const oca& item
);
/*!
ensures
- #get_oca() == item
!*/
const oca get_oca (
) const;
/*!
ensures
- returns a copy of the optimizer used to solve the SVM problem.
!*/
const kernel_type get_kernel (
) const;
/*!
ensures
- returns a copy of the kernel function in use by this object. Since the
linear kernels don't have any parameters this function just returns
kernel_type()
!*/
bool learns_nonnegative_weights (
) const;
/*!
ensures
- The output of training is a weight vector that defines the behavior of
the resulting decision function. That is, the decision function simply
takes the dot product between the learned weight vector and a test sample
and returns the result. Therefore, if learns_nonnegative_weights() == true
then the resulting learned weight vector will always have non-negative
entries.
!*/
void set_learns_nonnegative_weights (
bool value
);
/*!
ensures
- #learns_nonnegative_weights() == value
!*/
void set_c (
scalar_type C
);
/*!
requires
- C > 0
ensures
- #get_c() == C
!*/
const scalar_type get_c (
) const;
/*!
ensures
- returns the SVM regularization parameter. It is the parameter that
determines the trade off between trying to fit the training data exactly
or allowing more errors but hopefully improving the generalization of the
resulting classifier. Larger values encourage exact fitting while
smaller values of C may encourage better generalization.
!*/
const decision_function<kernel_type> train (
const std::vector<ranking_pair<sample_type> >& samples
) const;
/*!
requires
- is_ranking_problem(samples) == true
ensures
- trains a ranking support vector classifier given the training samples.
- returns a decision function F with the following properties:
- F.alpha.size() == 1
- F.basis_vectors.size() == 1
- F.alpha(0) == 1
- Given two vectors, A and B, then A is predicted to come before B
in the learned ranking if and only if F(A) > F(B).
!*/
const decision_function<kernel_type> train (
const ranking_pair<sample_type>& sample
) const;
/*!
requires
- is_ranking_problem(std::vector<ranking_pair<sample_type> >(1, sample)) == true
ensures
- This is just a convenience routine for calling the above train()
function. That is, it just copies sample into an appropriate std::vector
object and invokes the above train() method. That is, this function is
equivalent to invoking:
return train(std::vector<ranking_pair<sample_type> >(1, sample));
!*/
};
// ----------------------------------------------------------------------------------------
}
#endif // DLIB_SVM_RANK_TrAINER_ABSTRACT_H__
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