/usr/include/nearestneighbor.h is in libalglib-dev 2.6.0-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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Copyright (c) 2010, Sergey Bochkanov (ALGLIB project).
>>> SOURCE LICENSE >>>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation (www.fsf.org); either version 2 of the
License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
A copy of the GNU General Public License is available at
http://www.fsf.org/licensing/licenses
>>> END OF LICENSE >>>
*************************************************************************/
#ifndef _nearestneighbor_h
#define _nearestneighbor_h
#include "ap.h"
#include "ialglib.h"
#include "tsort.h"
struct kdtree
{
int n;
int nx;
int ny;
int normtype;
int distmatrixtype;
ap::real_2d_array xy;
ap::integer_1d_array tags;
ap::real_1d_array boxmin;
ap::real_1d_array boxmax;
ap::real_1d_array curboxmin;
ap::real_1d_array curboxmax;
double curdist;
ap::integer_1d_array nodes;
ap::real_1d_array splits;
ap::real_1d_array x;
int kneeded;
double rneeded;
bool selfmatch;
double approxf;
int kcur;
ap::integer_1d_array idx;
ap::real_1d_array r;
ap::real_1d_array buf;
int debugcounter;
};
/*************************************************************************
KD-tree creation
This subroutine creates KD-tree from set of X-values and optional Y-values
INPUT PARAMETERS
XY - dataset, array[0..N-1,0..NX+NY-1].
one row corresponds to one point.
first NX columns contain X-values, next NY (NY may be zero)
columns may contain associated Y-values
N - number of points, N>=1
NX - space dimension, NX>=1.
NY - number of optional Y-values, NY>=0.
NormType- norm type:
* 0 denotes infinity-norm
* 1 denotes 1-norm
* 2 denotes 2-norm (Euclidean norm)
OUTPUT PARAMETERS
KDT - KD-tree
NOTES
1. KD-tree creation have O(N*logN) complexity and O(N*(2*NX+NY)) memory
requirements.
2. Although KD-trees may be used with any combination of N and NX, they
are more efficient than brute-force search only when N >> 4^NX. So they
are most useful in low-dimensional tasks (NX=2, NX=3). NX=1 is another
inefficient case, because simple binary search (without additional
structures) is much more efficient in such tasks than KD-trees.
-- ALGLIB --
Copyright 28.02.2010 by Bochkanov Sergey
*************************************************************************/
void kdtreebuild(const ap::real_2d_array& xy,
int n,
int nx,
int ny,
int normtype,
kdtree& kdt);
/*************************************************************************
KD-tree creation
This subroutine creates KD-tree from set of X-values, integer tags and
optional Y-values
INPUT PARAMETERS
XY - dataset, array[0..N-1,0..NX+NY-1].
one row corresponds to one point.
first NX columns contain X-values, next NY (NY may be zero)
columns may contain associated Y-values
Tags - tags, array[0..N-1], contains integer tags associated
with points.
N - number of points, N>=1
NX - space dimension, NX>=1.
NY - number of optional Y-values, NY>=0.
NormType- norm type:
* 0 denotes infinity-norm
* 1 denotes 1-norm
* 2 denotes 2-norm (Euclidean norm)
OUTPUT PARAMETERS
KDT - KD-tree
NOTES
1. KD-tree creation have O(N*logN) complexity and O(N*(2*NX+NY)) memory
requirements.
2. Although KD-trees may be used with any combination of N and NX, they
are more efficient than brute-force search only when N >> 4^NX. So they
are most useful in low-dimensional tasks (NX=2, NX=3). NX=1 is another
inefficient case, because simple binary search (without additional
structures) is much more efficient in such tasks than KD-trees.
-- ALGLIB --
Copyright 28.02.2010 by Bochkanov Sergey
*************************************************************************/
void kdtreebuildtagged(const ap::real_2d_array& xy,
const ap::integer_1d_array& tags,
int n,
int nx,
int ny,
int normtype,
kdtree& kdt);
/*************************************************************************
K-NN query: K nearest neighbors
INPUT PARAMETERS
KDT - KD-tree
X - point, array[0..NX-1].
K - number of neighbors to return, K>=1
SelfMatch - whether self-matches are allowed:
* if True, nearest neighbor may be the point itself
(if it exists in original dataset)
* if False, then only points with non-zero distance
are returned
RESULT
number of actual neighbors found (either K or N, if K>N).
This subroutine performs query and stores its result in the internal
structures of the KD-tree. You can use following subroutines to obtain
these results:
* KDTreeQueryResultsX() to get X-values
* KDTreeQueryResultsXY() to get X- and Y-values
* KDTreeQueryResultsTags() to get tag values
* KDTreeQueryResultsDistances() to get distances
-- ALGLIB --
Copyright 28.02.2010 by Bochkanov Sergey
*************************************************************************/
int kdtreequeryknn(kdtree& kdt,
const ap::real_1d_array& x,
int k,
bool selfmatch);
/*************************************************************************
R-NN query: all points within R-sphere centered at X
INPUT PARAMETERS
KDT - KD-tree
X - point, array[0..NX-1].
R - radius of sphere (in corresponding norm), R>0
SelfMatch - whether self-matches are allowed:
* if True, nearest neighbor may be the point itself
(if it exists in original dataset)
* if False, then only points with non-zero distance
are returned
RESULT
number of neighbors found, >=0
This subroutine performs query and stores its result in the internal
structures of the KD-tree. You can use following subroutines to obtain
actual results:
* KDTreeQueryResultsX() to get X-values
* KDTreeQueryResultsXY() to get X- and Y-values
* KDTreeQueryResultsTags() to get tag values
* KDTreeQueryResultsDistances() to get distances
-- ALGLIB --
Copyright 28.02.2010 by Bochkanov Sergey
*************************************************************************/
int kdtreequeryrnn(kdtree& kdt,
const ap::real_1d_array& x,
double r,
bool selfmatch);
/*************************************************************************
K-NN query: approximate K nearest neighbors
INPUT PARAMETERS
KDT - KD-tree
X - point, array[0..NX-1].
K - number of neighbors to return, K>=1
SelfMatch - whether self-matches are allowed:
* if True, nearest neighbor may be the point itself
(if it exists in original dataset)
* if False, then only points with non-zero distance
are returned
Eps - approximation factor, Eps>=0. eps-approximate nearest
neighbor is a neighbor whose distance from X is at
most (1+eps) times distance of true nearest neighbor.
RESULT
number of actual neighbors found (either K or N, if K>N).
NOTES
significant performance gain may be achieved only when Eps is is on
the order of magnitude of 1 or larger.
This subroutine performs query and stores its result in the internal
structures of the KD-tree. You can use following subroutines to obtain
these results:
* KDTreeQueryResultsX() to get X-values
* KDTreeQueryResultsXY() to get X- and Y-values
* KDTreeQueryResultsTags() to get tag values
* KDTreeQueryResultsDistances() to get distances
-- ALGLIB --
Copyright 28.02.2010 by Bochkanov Sergey
*************************************************************************/
int kdtreequeryaknn(kdtree& kdt,
const ap::real_1d_array& x,
int k,
bool selfmatch,
double eps);
/*************************************************************************
X-values from last query
INPUT PARAMETERS
KDT - KD-tree
X - pre-allocated array, at least K rows, at least NX columns
OUTPUT PARAMETERS
X - K rows are filled with X-values
K - number of points
NOTE
points are ordered by distance from the query point (first = closest)
SEE ALSO
* KDTreeQueryResultsXY() X- and Y-values
* KDTreeQueryResultsTags() tag values
* KDTreeQueryResultsDistances() distances
-- ALGLIB --
Copyright 28.02.2010 by Bochkanov Sergey
*************************************************************************/
void kdtreequeryresultsx(const kdtree& kdt, ap::real_2d_array& x, int& k);
/*************************************************************************
X- and Y-values from last query
INPUT PARAMETERS
KDT - KD-tree
XY - pre-allocated array, at least K rows, at least NX+NY columns
OUTPUT PARAMETERS
X - K rows are filled with points: first NX columns with
X-values, next NY columns - with Y-values.
K - number of points
NOTE
points are ordered by distance from the query point (first = closest)
SEE ALSO
* KDTreeQueryResultsX() X-values
* KDTreeQueryResultsTags() tag values
* KDTreeQueryResultsDistances() distances
-- ALGLIB --
Copyright 28.02.2010 by Bochkanov Sergey
*************************************************************************/
void kdtreequeryresultsxy(const kdtree& kdt, ap::real_2d_array& xy, int& k);
/*************************************************************************
point tags from last query
INPUT PARAMETERS
KDT - KD-tree
Tags - pre-allocated array, at least K elements
OUTPUT PARAMETERS
Tags - first K elements are filled with tags associated with points,
or, when no tags were supplied, with zeros
K - number of points
NOTE
points are ordered by distance from the query point (first = closest)
SEE ALSO
* KDTreeQueryResultsX() X-values
* KDTreeQueryResultsXY() X- and Y-values
* KDTreeQueryResultsDistances() distances
-- ALGLIB --
Copyright 28.02.2010 by Bochkanov Sergey
*************************************************************************/
void kdtreequeryresultstags(const kdtree& kdt,
ap::integer_1d_array& tags,
int& k);
/*************************************************************************
Distances from last query
INPUT PARAMETERS
KDT - KD-tree
R - pre-allocated array, at least K elements
OUTPUT PARAMETERS
R - first K elements are filled with distances
(in corresponding norm)
K - number of points
NOTE
points are ordered by distance from the query point (first = closest)
SEE ALSO
* KDTreeQueryResultsX() X-values
* KDTreeQueryResultsXY() X- and Y-values
* KDTreeQueryResultsTags() tag values
-- ALGLIB --
Copyright 28.02.2010 by Bochkanov Sergey
*************************************************************************/
void kdtreequeryresultsdistances(const kdtree& kdt,
ap::real_1d_array& r,
int& k);
#endif
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