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Moved create_random_projection_hash() into its own file.

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Davis King 2011-12-25 12:14:17 -05:00
parent 320d56cea8
commit 5f19180473
5 changed files with 120 additions and 83 deletions
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1
dlib/lsh.h
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@ -5,6 +5,7 @@
#include "lsh/projection_hash.h"
#include "lsh/create_random_projection_hash.h"
#endif // DLIB_LSh_

93
dlib/lsh/create_random_projection_hash.h Normal file
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@ -0,0 +1,93 @@
// Copyright (C) 2011 Davis E. King (davis@dlib.net)
// License: Boost Software License See LICENSE.txt for the full license.
#ifndef DLIB_CREATE_RANDOM_PROJECTION_HAsH_H__
#define DLIB_CREATE_RANDOM_PROJECTION_HAsH_H__
#include "create_random_projection_hash_abstract.h"
#include "projection_hash.h"
#include "../matrix.h"
#include "../rand.h"
#include <vector>
namespace dlib
{
// ----------------------------------------------------------------------------------------
template <typename vector_type>
projection_hash create_random_projection_hash (
const vector_type& v,
const int bits
)
{
// compute a whitening matrix
matrix<double> whiten = trans(chol(pinv(covariance(vector_to_matrix(v)))));
// hashes
std::vector<unsigned long> h(v.size(),0);
std::vector<double> vals(v.size(),0);
// number of hits for each hash value
std::vector<unsigned long> counts;
std::vector<double> temp;
// build a random projection matrix
dlib::rand rnd;
matrix<double> proj(bits, v[0].size());
for (long r = 0; r < proj.nr(); ++r)
for (long c = 0; c < proj.nc(); ++c)
proj(r,c) = rnd.get_random_gaussian();
// merge whitening matrix with projection matrix
proj = proj*whiten;
matrix<double,0,1> offset(bits);
// figure out what the offset values should be
for (int itr = 0; itr < offset.size(); ++itr)
{
counts.assign(std::pow(2,bits), 0);
// count the popularity of each hash value
for (unsigned long i = 0; i < h.size(); ++i)
{
h[i] <<= 1;
counts[h[i]] += 1;
}
const unsigned long max_h = index_of_max(vector_to_matrix(counts));
temp.clear();
for (unsigned long i = 0; i < v.size(); ++i)
{
vals[i] = dot(rowm(proj,itr), v[i]);
if (h[i] == max_h)
temp.push_back(vals[i]);
}
// split down the middle
std::sort(temp.begin(), temp.end());
const double split = temp[temp.size()/2];
offset(itr) = -split;
for (unsigned long i = 0; i < vals.size(); ++i)
{
if (vals[i] - split > 0)
h[i] |= 1;
}
}
return projection_hash(proj, offset);
}
// ----------------------------------------------------------------------------------------
}
#endif // DLIB_CREATE_RANDOM_PROJECTION_HAsH_H__

26
dlib/lsh/create_random_projection_hash_abstract.h Normal file
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@ -0,0 +1,26 @@
// Copyright (C) 2011 Davis E. King (davis@dlib.net)
// License: Boost Software License See LICENSE.txt for the full license.
#undef DLIB_CREATE_RANDOM_PROJECTION_HAsH_ABSTRACT_H__
#ifdef DLIB_CREATE_RANDOM_PROJECTION_HAsH_ABSTRACT_H__
#include "projection_hash_abstract.h"
#include "../rand.h"
namespace dlib
{
// ----------------------------------------------------------------------------------------
template <typename vector_type>
projection_hash create_random_projection_hash (
const vector_type& v,
const int bits
);
// ----------------------------------------------------------------------------------------
}
#endif // DLIB_CREATE_RANDOM_PROJECTION_HAsH_ABSTRACT_H__

73
dlib/lsh/projection_hash.h
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@ -89,79 +89,6 @@ namespace dlib
item = projection_hash(proj, offset);
}
// ----------------------------------------------------------------------------------------
template <typename vector_type>
projection_hash create_random_projection_hash (
const vector_type& v,
const int bits
)
{
// compute a whitening matrix
matrix<double> whiten = trans(chol(pinv(covariance(vector_to_matrix(v)))));
// hashes
std::vector<unsigned long> h(v.size(),0);
std::vector<double> vals(v.size(),0);
// number of hits for each hash value
std::vector<unsigned long> counts;
std::vector<double> temp;
// build a random projection matrix
dlib::rand rnd;
matrix<double> proj(bits, v[0].size());
for (long r = 0; r < proj.nr(); ++r)
for (long c = 0; c < proj.nc(); ++c)
proj(r,c) = rnd.get_random_gaussian();
// merge whitening matrix with projection matrix
proj = proj*whiten;
matrix<double,0,1> offset(bits);
// figure out what the offset values should be
for (int itr = 0; itr < offset.size(); ++itr)
{
counts.assign(std::pow(2,bits), 0);
// count the popularity of each hash value
for (unsigned long i = 0; i < h.size(); ++i)
{
h[i] <<= 1;
counts[h[i]] += 1;
}
const unsigned long max_h = index_of_max(vector_to_matrix(counts));
temp.clear();
for (unsigned long i = 0; i < v.size(); ++i)
{
vals[i] = dot(rowm(proj,itr), v[i]);
if (h[i] == max_h)
temp.push_back(vals[i]);
}
// split down the middle
std::sort(temp.begin(), temp.end());
const double split = temp[temp.size()/2];
offset(itr) = -split;
for (unsigned long i = 0; i < vals.size(); ++i)
{
if (vals[i] - split > 0)
h[i] |= 1;
}
}
return projection_hash(proj, offset);
}
// ----------------------------------------------------------------------------------------
}

10
dlib/lsh/projection_hash_abstract.h
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@ -4,8 +4,6 @@
#ifdef DLIB_PROJECTION_HASh_ABSTRACT_H__
#include "../matrix.h"
#include "../rand.h"
#include <vector>
namespace dlib
{
@ -55,14 +53,6 @@ namespace dlib
std::istream& in
);
// ----------------------------------------------------------------------------------------
template <typename vector_type>
projection_hash create_random_projection_hash (
const vector_type& v,
const int bits
);
// ----------------------------------------------------------------------------------------
}