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Merge pull request #2071 from pemmanuelviel:LshOrthogonalSubvectors

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This commit is contained in:
Vadim Pisarevsky 2014-07-02 14:24:09 +00:00
commit 8539d424b2
2 changed files with 21 additions and 9 deletions
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14
modules/flann/include/opencv2/flann/lsh_index.h
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@ -109,10 +109,22 @@ public:
*/ */
void buildIndex() void buildIndex()
{ {
std::vector<size_t> indices(feature_size_ * CHAR_BIT);
tables_.resize(table_number_); tables_.resize(table_number_);
for (unsigned int i = 0; i < table_number_; ++i) { for (unsigned int i = 0; i < table_number_; ++i) {
//re-initialize the random indices table that the LshTable will use to pick its sub-dimensions
if( (indices.size() == feature_size_ * CHAR_BIT) || (indices.size() < key_size_) )
{
indices.resize( feature_size_ * CHAR_BIT );
for (size_t j = 0; j < feature_size_ * CHAR_BIT; ++j)
indices[j] = j;
std::random_shuffle(indices.begin(), indices.end());
}
lsh::LshTable<ElementType>& table = tables_[i]; lsh::LshTable<ElementType>& table = tables_[i];
table = lsh::LshTable<ElementType>(feature_size_, key_size_); table = lsh::LshTable<ElementType>(feature_size_, key_size_, indices);
// Add the features to the table // Add the features to the table
table.add(dataset_); table.add(dataset_);

16
modules/flann/include/opencv2/flann/lsh_table.h
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@ -153,7 +153,7 @@ public:
* @param feature_size is the size of the feature (considered as a ElementType[]) * @param feature_size is the size of the feature (considered as a ElementType[])
* @param key_size is the number of bits that are turned on in the feature * @param key_size is the number of bits that are turned on in the feature
*/ */
LshTable(unsigned int /*feature_size*/, unsigned int /*key_size*/) LshTable(unsigned int /*feature_size*/, unsigned int /*key_size*/, std::vector<size_t> & /*indices*/)
{ {
std::cerr << "LSH is not implemented for that type" << std::endl; std::cerr << "LSH is not implemented for that type" << std::endl;
assert(0); assert(0);
@ -341,20 +341,20 @@ private:
// Specialization for unsigned char // Specialization for unsigned char
template<> template<>
inline LshTable<unsigned char>::LshTable(unsigned int feature_size, unsigned int subsignature_size) inline LshTable<unsigned char>::LshTable( unsigned int feature_size,
unsigned int subsignature_size,
std::vector<size_t> & indices )
{ {
initialize(subsignature_size); initialize(subsignature_size);
// Allocate the mask // Allocate the mask
mask_ = std::vector<size_t>((size_t)ceil((float)(feature_size * sizeof(char)) / (float)sizeof(size_t)), 0); mask_ = std::vector<size_t>((size_t)ceil((float)(feature_size * sizeof(char)) / (float)sizeof(size_t)), 0);
// A bit brutal but fast to code
std::vector<size_t> indices(feature_size * CHAR_BIT);
for (size_t i = 0; i < feature_size * CHAR_BIT; ++i) indices[i] = i;
std::random_shuffle(indices.begin(), indices.end());
// Generate a random set of order of subsignature_size_ bits // Generate a random set of order of subsignature_size_ bits
for (unsigned int i = 0; i < key_size_; ++i) { for (unsigned int i = 0; i < key_size_; ++i) {
size_t index = indices[i]; //Ensure the Nth bit will be selected only once among the different LshTables
//to avoid having two different tables with signatures sharing many dimensions/many bits
size_t index = indices[0];
indices.erase( indices.begin() );
// Set that bit in the mask // Set that bit in the mask
size_t divisor = CHAR_BIT * sizeof(size_t); size_t divisor = CHAR_BIT * sizeof(size_t);