void LSHSearch<SortPolicy>::
Search(const size_t k,
arma::Mat<size_t>& resultingNeighbors,
arma::mat& distances,
const size_t numTablesToSearch)
{
// Set the size of the neighbor and distance matrices.
resultingNeighbors.set_size(k, querySet.n_cols);
distances.set_size(k, querySet.n_cols);
distances.fill(SortPolicy::WorstDistance());
resultingNeighbors.fill(referenceSet.n_cols);
size_t avgIndicesReturned = 0;
Timer::Start("computing_neighbors");
// Go through every query point sequentially.
for (size_t i = 0; i < querySet.n_cols; i++)
{
// Hash every query into every hash table and eventually into the
// 'secondHashTable' to obtain the neighbor candidates.
arma::uvec refIndices;
ReturnIndicesFromTable(i, refIndices, numTablesToSearch);
// An informative book-keeping for the number of neighbor candidates
// returned on average.
avgIndicesReturned += refIndices.n_elem;
// Sequentially go through all the candidates and save the best 'k'
// candidates.
for (size_t j = 0; j < refIndices.n_elem; j++)
BaseCase(distances, resultingNeighbors, i, (size_t) refIndices[j]);
}
Timer::Stop("computing_neighbors");
distanceEvaluations += avgIndicesReturned;
avgIndicesReturned /= querySet.n_cols;
Log::Info << avgIndicesReturned << " distinct indices returned on average." <<
std::endl;
}
void DefaultEvaluatorForIntegralOperators<BasisFunctionType, KernelType,
ResultType, GeometryFactory>::evaluate(
Region region,
const arma::Mat<CoordinateType>& points, arma::Mat<ResultType>& result) const
{
const size_t pointCount = points.n_cols;
const int outputComponentCount = m_integral->resultDimension();
result.set_size(outputComponentCount, pointCount);
result.fill(0.);
const GeometricalData<CoordinateType>& trialGeomData =
(region == EvaluatorForIntegralOperators<ResultType>::NEAR_FIELD) ?
m_nearFieldTrialGeomData :
m_farFieldTrialGeomData;
const CollectionOf2dArrays<ResultType>& trialTransfValues =
(region == EvaluatorForIntegralOperators<ResultType>::NEAR_FIELD) ?
m_nearFieldTrialTransfValues :
m_farFieldTrialTransfValues;
const std::vector<CoordinateType>& weights =
(region == EvaluatorForIntegralOperators<ResultType>::NEAR_FIELD) ?
m_nearFieldWeights :
m_farFieldWeights;
// Do things in chunks of 96 points -- in order to avoid creating
// too large arrays of kernel values
const size_t chunkSize = 96;
const size_t chunkCount = (pointCount + chunkSize - 1) / chunkSize;
int maxThreadCount = 1;
if (!m_parallelizationOptions.isOpenClEnabled()) {
if (m_parallelizationOptions.maxThreadCount() ==
ParallelizationOptions::AUTO)
maxThreadCount = tbb::task_scheduler_init::automatic;
else
maxThreadCount = m_parallelizationOptions.maxThreadCount();
}
tbb::task_scheduler_init scheduler(maxThreadCount);
typedef EvaluationLoopBody<
BasisFunctionType, KernelType, ResultType> Body;
{
Fiber::SerialBlasRegion region;
tbb::parallel_for(tbb::blocked_range<size_t>(0, chunkCount),
Body(chunkSize,
points, trialGeomData, trialTransfValues, weights,
*m_kernels, *m_integral, result));
}
// // Old serial version
// CollectionOf4dArrays<KernelType> kernelValues;
// GeometricalData<CoordinateType> evalPointGeomData;
// for (size_t start = 0; start < pointCount; start += chunkSize)
// {
// size_t end = std::min(start + chunkSize, pointCount);
// evalPointGeomData.globals = points.cols(start, end - 1 /* inclusive */);
// m_kernels->evaluateOnGrid(evalPointGeomData, trialGeomData, kernelValues);
// // View into the current chunk of the "result" array
// _2dArray<ResultType> resultChunk(outputComponentCount, end - start,
// result.colptr(start));
// m_integral->evaluate(trialGeomData,
// kernelValues,
// weightedTrialTransfValues,
// resultChunk);
// }
}
void CF<FactorizerType>::GetRecommendations(const size_t numRecs,
arma::Mat<size_t>& recommendations,
arma::Col<size_t>& users)
{
// Generate new table by multiplying approximate values.
rating = w * h;
// Now, we will use the decomposed w and h matrices to estimate what the user
// would have rated items as, and then pick the best items.
// Temporarily store feature vector of queried users.
arma::mat query(rating.n_rows, users.n_elem);
// Select feature vectors of queried users.
for (size_t i = 0; i < users.n_elem; i++)
query.col(i) = rating.col(users(i));
// Temporary storage for neighborhood of the queried users.
arma::Mat<size_t> neighborhood;
// Calculate the neighborhood of the queried users.
// This should be a templatized option.
neighbor::AllkNN a(rating);
arma::mat resultingDistances; // Temporary storage.
a.Search(query, numUsersForSimilarity, neighborhood, resultingDistances);
// Temporary storage for storing the average rating for each user in their
// neighborhood.
arma::mat averages = arma::zeros<arma::mat>(rating.n_rows, query.n_cols);
// Iterate over each query user.
for (size_t i = 0; i < neighborhood.n_cols; ++i)
{
// Iterate over each neighbor of the query user.
for (size_t j = 0; j < neighborhood.n_rows; ++j)
averages.col(i) += rating.col(neighborhood(j, i));
// Normalize average.
averages.col(i) /= neighborhood.n_rows;
}
// Generate recommendations for each query user by finding the maximum numRecs
// elements in the averages matrix.
recommendations.set_size(numRecs, users.n_elem);
recommendations.fill(cleanedData.n_rows); // Invalid item number.
arma::mat values(numRecs, users.n_elem);
values.fill(-DBL_MAX); // The smallest possible value.
for (size_t i = 0; i < users.n_elem; i++)
{
// Look through the averages column corresponding to the current user.
for (size_t j = 0; j < averages.n_rows; ++j)
{
// Ensure that the user hasn't already rated the item.
if (cleanedData(j, users(i)) != 0.0)
continue; // The user already rated the item.
// Is the estimated value better than the worst candidate?
const double value = averages(j, i);
if (value > values(values.n_rows - 1, i))
{
// It should be inserted. Which position?
size_t insertPosition = values.n_rows - 1;
while (insertPosition > 0)
{
if (value <= values(insertPosition - 1, i))
break; // The current value is the right one.
insertPosition--;
}
// Now insert it into the list.
InsertNeighbor(i, insertPosition, j, value, recommendations,
values);
}
}
// If we were not able to come up with enough recommendations, issue a
// warning.
if (recommendations(values.n_rows - 1, i) == cleanedData.n_rows + 1)
Log::Warn << "Could not provide " << values.n_rows << " recommendations "
<< "for user " << users(i) << " (not enough un-rated items)!"
<< std::endl;
}
}
void CF::GetRecommendations(const size_t numRecs,
arma::Mat<size_t>& recommendations,
arma::Col<size_t>& users)
{
// We want to avoid calculating the full rating matrix, so we will do nearest
// neighbor search only on the H matrix, using the observation that if the
// rating matrix X = W*H, then d(X.col(i), X.col(j)) = d(W H.col(i), W
// H.col(j)). This can be seen as nearest neighbor search on the H matrix
// with the Mahalanobis distance where M^{-1} = W^T W. So, we'll decompose
// M^{-1} = L L^T (the Cholesky decomposition), and then multiply H by L^T.
// Then we can perform nearest neighbor search.
arma::mat l = arma::chol(w.t() * w);
arma::mat stretchedH = l * h; // Due to the Armadillo API, l is L^T.
// Now, we will use the decomposed w and h matrices to estimate what the user
// would have rated items as, and then pick the best items.
// Temporarily store feature vector of queried users.
arma::mat query(stretchedH.n_rows, users.n_elem);
// Select feature vectors of queried users.
for (size_t i = 0; i < users.n_elem; i++)
query.col(i) = stretchedH.col(users(i));
// Temporary storage for neighborhood of the queried users.
arma::Mat<size_t> neighborhood;
// Calculate the neighborhood of the queried users.
// This should be a templatized option.
neighbor::KNN a(stretchedH);
arma::mat resultingDistances; // Temporary storage.
a.Search(query, numUsersForSimilarity, neighborhood, resultingDistances);
// Generate recommendations for each query user by finding the maximum numRecs
// elements in the averages matrix.
recommendations.set_size(numRecs, users.n_elem);
recommendations.fill(cleanedData.n_rows); // Invalid item number.
arma::mat values(numRecs, users.n_elem);
values.fill(-DBL_MAX); // The smallest possible value.
for (size_t i = 0; i < users.n_elem; i++)
{
// First, calculate average of neighborhood values.
arma::vec averages;
averages.zeros(cleanedData.n_rows);
for (size_t j = 0; j < neighborhood.n_rows; ++j)
averages += w * h.col(neighborhood(j, i));
averages /= neighborhood.n_rows;
// Look through the averages column corresponding to the current user.
for (size_t j = 0; j < averages.n_rows; ++j)
{
// Ensure that the user hasn't already rated the item.
if (cleanedData(j, users(i)) != 0.0)
continue; // The user already rated the item.
// Is the estimated value better than the worst candidate?
const double value = averages[j];
if (value > values(values.n_rows - 1, i))
{
// It should be inserted. Which position?
size_t insertPosition = values.n_rows - 1;
while (insertPosition > 0)
{
if (value <= values(insertPosition - 1, i))
break; // The current value is the right one.
insertPosition--;
}
// Now insert it into the list.
InsertNeighbor(i, insertPosition, j, value, recommendations,
values);
}
}
// If we were not able to come up with enough recommendations, issue a
// warning.
if (recommendations(values.n_rows - 1, i) == cleanedData.n_rows + 1)
Log::Warn << "Could not provide " << values.n_rows << " recommendations "
<< "for user " << users(i) << " (not enough un-rated items)!"
<< std::endl;
}
}
