source: trunk/yat/classifier/KernelLookup.h

Last change on this file was 4019, checked in by Peter, 11 months ago

merge 0.18 into trunk

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1#ifndef _theplu_yat_classifier_kernel_lookup_
2#define _theplu_yat_classifier_kernel_lookup_
3
4// $Id$
5
6/*
7  Copyright (C) 2005 Jari Häkkinen, Peter Johansson
8  Copyright (C) 2006 Jari Häkkinen, Peter Johansson, Markus Ringnér
9  Copyright (C) 2007, 2008 Jari Häkkinen, Peter Johansson
10  Copyright (C) 2010, 2012, 2020 Peter Johansson
11
12  This file is part of the yat library, http://dev.thep.lu.se/yat
13
14  The yat library is free software; you can redistribute it and/or
15  modify it under the terms of the GNU General Public License as
16  published by the Free Software Foundation; either version 3 of the
17  License, or (at your option) any later version.
18
19  The yat library is distributed in the hope that it will be useful,
20  but WITHOUT ANY WARRANTY; without even the implied warranty of
21  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
22  General Public License for more details.
23
24  You should have received a copy of the GNU General Public License
25  along with yat. If not, see <http://www.gnu.org/licenses/>.
26*/
27
28#include "Kernel.h"
29#include "yat/utility/Container2DIterator.h"
30#include "yat/utility/Index.h"
31#include "yat/utility/iterator_traits.h"
32#include "yat/utility/StrideIterator.h"
33
34#include <memory>
35
36namespace theplu {
37namespace yat {
38namespace classifier {
39
40  class KernelFunction;
41  class MatrixLookup;
42  class MatrixLookupWeighted;
43
44  ///
45  /// @brief Lookup into Kernel
46  ///
47  /// This is the KernelLookup class to be used together with kernel
48  /// methods such as Support Vector Machines (SVM). The class does
49  /// not contain any data or values, but rather is a lookup into a
50  /// Kernel object. Each row and each column corresponds to a row and
51  /// a column in the Kernel, respectively. This design allows for fast
52  /// creation of sub-kernels, which is a common operation in most
53  /// traning/validation procedures.
54  ///
55  /// A KernelLookup can be created directly from a Kernel or from
56  /// another KernelLookup. In the latter case, the resulting
57  /// KernelLookup is looking directly into the underlying Kernel to
58  /// avoid multiple lookups.
59  ///
60  /// There is a possibility to set the KernelLookup as owner of the
61  /// underlying kernel. This implies that underlying kernel is deleted
62  /// in destructor of MatrixLookup, but only if there is no other
63  /// owner of the underlying kernel. A reference counter is used to
64  /// keep track of number of owners. Ownership is copied in copy
65  /// constructors and assignments.
66  ///
67  class KernelLookup
68  {
69
70  public:
71    /**
72       value_type is double
73
74       \since New in yat 0.5
75     */
76    typedef double value_type;
77
78    /**
79       const_reference type is const double
80
81       \since New in yat 0.5
82     */
83    typedef const double const_reference;
84
85    /// 'Read Only' iterator
86    typedef utility::StrideIterator<
87    utility::Container2DIterator<const KernelLookup, const double,
88                                 const_reference> >
89    const_iterator;
90
91    /**
92       'Read only' iterator intended to iterate over a column
93     */
94    typedef const_iterator const_column_iterator;
95
96    /**
97       'Read only' iterator intended to iterate over a row
98     */
99    typedef const_iterator const_row_iterator;
100
101    ///
102    /// @brief Constructor a Lookup into a Kernel
103    ///
104    /// Constructs a KernelLookup corresponding to the Kernel @a
105    /// kernel. By default @a owner is set to false, which means
106    /// KernelLookup does not own the underlying Kernel.
107    ///
108    /// @note If underlying Kernel goes out of scope or is deleted, the
109    /// KernelLookup becomes invalid and the result of further use is
110    /// undefined.
111    ///
112    /// @note Do not construct two KernelLookups from the same @a
113    /// kernel with @a owner set to true because that will cause
114    /// multiple deletion of @a kernel.
115    ///
116    KernelLookup(const Kernel& kernel, const bool owner=false);
117
118    ///
119    /// @brief Constructing a Lookup into a subKernel
120    ///
121    /// Creating a Lookup into parts of the Kernel. In the created
122    /// Lookup the element in the \f$ i \f$ th row in the \f$ j \f$ th
123    /// column is identical to the element in row row[i] and columns
124    /// column[j] in the underlying @a kernel. If @a owner is set to
125    /// true yhe underlying @a kernel is destroyed in the destructor.
126    ///
127    /// @note If @a kernel goes out of scope or is deleted, the
128    /// returned pointer becomes invalid and the result of further use is
129    /// undefined.
130    ///
131    /// @note For training usage row index shall always be equal to
132    /// column index.
133    ///
134    KernelLookup(const Kernel& kernel, const utility::Index& row, 
135                 const utility::Index& column, const bool owner=false);
136
137    ///
138    /// @brief Copy constructor.
139    ///
140    /// A Lookup is created looking into the
141    /// same underlying Kernel as @a kl is looking into.
142    ///
143    /// If \a kl is owner of underlying data, constructed
144    /// KernelLookup will also be set as owner of underlying data.
145    ///
146    KernelLookup(const KernelLookup& kl);
147
148
149    ///
150    /// @brief Contructing a sub-KernelLookup.
151    ///
152    /// Contructor building a sub-KernelLookup from a KernelLookup
153    /// defined by row index vector and column index vector. In the
154    /// created Lookup the element in the \f$ i \f$ th row in the
155    /// \f$ j \f$ th column is identical to the element in row row[i] and
156    /// columns column[j] in the copied @a kl. The resulting
157    /// KernelLookup is independent of the old KernelLookup, but is
158    /// undefined in case underlying Kernel is destroyed.
159    ///
160    /// If \a kl is owner of underlying data, constructed
161    /// KernelLookup will also be set as owner of underlying data.
162    ///
163    /// @note For training usage row index shall always be equal to
164    /// column index.
165    ///
166    KernelLookup(const KernelLookup& kl, const utility::Index& row, 
167                 const utility::Index& column);
168
169    ///
170    /// Constructor taking the column (default) or row index as
171    /// input. If @a row is false the created KernelLookup will have
172    /// equally many rows as @a kernel.
173    ///
174    /// If \a kl is owner of underlying data, constructed
175    /// KernelLookup will also be set as owner of underlying data.
176    ///
177    /// @note If underlying kernel goes out of scope or is deleted, the
178    /// KernelLookup becomes invalid and the result of further use is
179    /// undefined.
180    ///
181    KernelLookup(const KernelLookup& kl, const utility::Index&, 
182                 const bool row=false);
183
184    ///
185    /// @brief Destructor
186    ///
187    /// Deletes underlying Kernel if KernelLookup owns it and there is
188    /// no other owner.
189    ///
190    virtual ~KernelLookup(void);
191
192    /**
193       Iterator iterates along a row. When end of row is reached it
194       jumps to beginning of next row.
195
196       \return const_iterator pointing to upper-left element.
197     */
198    const_iterator begin(void) const;
199
200    /**
201       Iterator iterates along a column.
202
203       \return iterator pointing to first element of column \a i.
204     */
205    const_column_iterator begin_column(size_t) const;
206
207    /**
208       Iterator iterates along a column.
209
210       \return const_iterator pointing to first element of column \a i.
211     */
212    const_row_iterator begin_row(size_t) const;
213
214    /**
215       \return number of columns
216    */
217    size_t columns(void) const;
218
219    ///
220    /// Each column in returned DataLookup corresponds to the column
221    /// in KernelLookup.
222    ///
223    /// \return data that KernelLookup is built upon.
224    ///
225    /// \throw if KernelLookup is weighted
226    ///
227    MatrixLookup data(void) const;
228
229    ///
230    /// Each column in returned DataLookup corresponds to the column
231    /// in KernelLookup.
232    ///
233    /// \return data that KernelLookup is built upon.
234    ///
235    /// \throw if KernelLookup is unweighted
236    ///
237    MatrixLookupWeighted data_weighted(void) const;
238
239    /**
240       Function to calculate a new Kernel element using the underlying
241       KernelFunction. The value is calculated between @a vec and the
242       data vector of the \a i th sample, in other words, the
243       sample corresponding to the \a i th row.
244    */
245    double element(const DataLookup1D& vec, size_t i) const;
246
247    /**
248       Function to calculate a new Kernel element using the underlying
249       KernelFunction. The value is calulated between @a vec and the
250       data vector of the \f$ i \f$ th sample, in other words, the
251       sample corresponding to the \f$ i \f$ th row or \f$ i \f$ th
252       column. In case KernelLookup is a sub-Kernel and not symmetric,
253       the kernel value is calculated between @a vec and the data
254       vector corresponding to \f$ i \f$ th row.
255    */
256    double element(const DataLookupWeighted1D& vec, size_t i) const;
257
258    /**
259       \return const_iterator pointing to end of matrix
260     */
261    const_iterator end(void) const;
262
263    /**
264       \return const_iterator pointing to end of column \a i
265     */
266    const_column_iterator end_column(size_t) const;
267
268    /**
269       \return const_iterator pointing to end of row \a i
270     */
271    const_row_iterator end_row(size_t) const;
272
273    /**
274       \return number of rows
275    */
276    size_t rows(void) const;
277
278    /**
279       Each element in returned KernelLookup is calculated using only
280       selected features (defined by @a index). Each element
281       corresponds to the same pair of samples as in the original
282       KernelLookup.
283    */
284    KernelLookup selected(const utility::Index& index) const;
285   
286    /**
287       This function is useful when predicting on an independent data
288       set using a kernel-based classifier. In returned KernelLookup
289       column \f$ i \f$ corresponds to column \f$ i \f$ in @a
290       data. Row \f$ i \f$ in returned KernelLookup corresponds to
291       same sample as row \f$ i \f$ in @a this. In other words, this
292       function returns a KernelLookup containing the kernel elements
293       between the passed @a data and the internal underlying data @a
294       this was built from.
295    */
296    KernelLookup test_kernel(const MatrixLookup& data) const;
297
298    /**
299       This function is useful when predicting on an independent data
300       set using a kernel-based classifier. In returned KernelLookup
301       column \f$ i \f$ corresponds to column \f$ i \f$ in @a
302       data. Row \f$ i \f$ in returned KernelLookup corresponds to
303       same sample as row \f$ i \f$ in @a this. In other words, this
304       function returns a KernelLookup containing the kernel elements
305       between the passed @a data and the internal underlying data @a
306       this was built from.
307    */
308    KernelLookup test_kernel(const MatrixLookupWeighted& data) const;
309
310    /**
311       \return true if underlying Kernel is weighted
312    */
313    bool weighted(void) const;
314
315    /**
316       \return element at position (\a row, \a column) in the Kernel
317       matrix
318    */
319    const_reference operator()(size_t row, size_t column) const;
320
321  private:
322    const KernelLookup& operator=(const KernelLookup&);
323    bool validate(const utility::Index&) const;
324
325    utility::Index column_index_;
326    std::shared_ptr<const Kernel> kernel_;
327    utility::Index row_index_;
328  }; // class KernelLookup
329
330}}} // of namespace classifier, yat, and theplu
331
332#endif
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