From: Benjamin Auder Date: Mon, 6 Dec 2021 23:29:59 +0000 (+0100) Subject: First commit X-Git-Url: https://git.auder.net/doc/html/%7B%7B%20asset%28%27mixstore/css/%3C?a=commitdiff_plain;h=762721a5fca14cf810160923bd855e82b827b5b5;p=nngd.git First commit --- 762721a5fca14cf810160923bd855e82b827b5b5 diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..57d912a --- /dev/null +++ b/.gitignore @@ -0,0 +1,9 @@ +/NAMESPACE +/man/ +!/man/nngd-package.Rd +/R/RcppExports.R +/src/RcppExports.cpp +/src/*.o +/src/*.so +.RData +.Rhistory diff --git a/DESCRIPTION b/DESCRIPTION new file mode 100644 index 0000000..e882735 --- /dev/null +++ b/DESCRIPTION @@ -0,0 +1,14 @@ +Package: nngd +Type: Package +Title: Compute distances based on the nearest-neighbors graph. +Version: 1.0 +Date: 2021-12-06 +Author: Benjamin Auder [aut,cre] +Maintainer: Benjamin Auder +Description: Only two functions for now. nng() builds the nearest-neighbors graph, + and ectd() computes the Euclidian Commute-Time Distances. + Only undirected graph case implemented so far. +License: MIT + file LICENSE +Imports: Rcpp, RcppEigen, igraph, pracma +LinkingTo: Rcpp, RcppEigen +RoxygenNote: 7.1.2 diff --git a/LICENSE b/LICENSE new file mode 100644 index 0000000..9f4ff56 --- /dev/null +++ b/LICENSE @@ -0,0 +1,2 @@ +YEAR: 2021-2021 +COPYRIGHT HOLDER: Benjamin Auder diff --git a/R/NAMESPACE.R b/R/NAMESPACE.R new file mode 100644 index 0000000..f213ec4 --- /dev/null +++ b/R/NAMESPACE.R @@ -0,0 +1,7 @@ +#' @useDynLib nngd, .registration = TRUE +#' +#' @importFrom igraph is_directed vcount as_edgelist components graph_from_edgelist +#' @importFrom pracma pinv +#' @import Rcpp +#' +NULL diff --git a/R/ectd.R b/R/ectd.R new file mode 100644 index 0000000..727bbd4 --- /dev/null +++ b/R/ectd.R @@ -0,0 +1,43 @@ +#' Compute the Euclidian Commute-Time Distances (ECTD) in an undirected graph. +#' +#' Assuming similarity function doesn't depend on x, and undirected graph. +#' +#' @param o Output of \code{nng}. +#' @param similarity function distance --> similarity. +#' @param inf.replace Replace Inf values by large finite number ? +#' +#' @return A distances matrix (n x n) +#' +#' @export +ectd <- function(o, similarity=function(x) 1, inf.replace=TRUE) +{ + if (!igraph::is_directed(o$graph)) + stop("Directed graph case unimplemented yet") + n <- igraph::vcount(o$graph) + E <- igraph::as_edgelist(o$graph, names=FALSE) + W <- matrix(0, nrow=n, ncol=n) + for (i in seq_len(nrow(E))) { + edge <- c(E[i,1], E[i,2]) + W[edge[1], edge[2]] <- similarity(o$distances[i]) + W[edge[2], edge[1]] <- W[edge[1], edge[2]] + } + L <- diag(rowSums(W)) - W + cc <- igraph::components(o$graph) + distances <- matrix(Inf, nrow=n, ncol=n) + for (i in seq_len(cc$no)) { + indices <- which(cc$membership == i) + L_loc <- L[indices, indices] + n_loc <- cc$csize[i] + if (n_loc >= 2) L_inv = pracma::pinv(L_loc) + else L_inv = matrix(ifelse(L_loc != 0, 1/L_loc[1], 0)) + Lii = matrix(rep(diag(L_inv), each=n_loc), nrow=n_loc, byrow=TRUE) + Ljj = matrix(rep(diag(L_inv), each=n_loc), nrow=n_loc) + # https://math.stackexchange.com/questions/1321305/commute-time-distance-in-a-graph + distances[indices, indices] <- Lii + Ljj - 2 * L_inv + } + if (inf.replace) { + finiteMax <- max(distances[is.finite(distances)]) + distances[is.infinite(distances)] <- finiteMax + 1 + } + distances +} diff --git a/R/nng.R b/R/nng.R new file mode 100644 index 0000000..6f3a34d --- /dev/null +++ b/R/nng.R @@ -0,0 +1,19 @@ +#' Compute the nearest-neighbors graph + pairwise distances. +#' +#' This is just a wrapper around C++/Rcpp function. +#' +#' @param data data.frame or matrix. +#' @param k Number of neighbors at each point. +#' @param mutual Whether or not to build mutual kNN graph. +#' +#' @return A list with $graph and $distances. +#' +#' @export +nng <- function(data, k=ceil(sqrt(nrow(data))), mutual=TRUE) +{ + mdata <- data + if (is.data.frame(data)) mdata <- as.matrix(data) + res <- findNeighbors(mdata, k, mutual) + list(graph = igraph::graph_from_edgelist(t(res$edges), directed = !mutual), + distances = sqrt(res$euc_dists)) +} diff --git a/README.md b/README.md new file mode 100644 index 0000000..8dba5e4 --- /dev/null +++ b/README.md @@ -0,0 +1,16 @@ +# nngd + +Build nearest-neighbors graph in a ~efficient way. + +Compute graph distances + ECTD distances. + +Use file knncpp.h from https://github.com/Rookfighter/knn-cpp : +wget https://raw.githubusercontent.com/Rookfighter/knn-cpp/master/include/knncpp.h + +## Usage + +roxygenize(".") +R CMD INSTALL . +library(nngd) +?nng +?ectd diff --git a/src/knncpp.h b/src/knncpp.h new file mode 100644 index 0000000..05d98ec --- /dev/null +++ b/src/knncpp.h @@ -0,0 +1,1726 @@ +/* knncpp.h + * + * Author: Fabian Meyer + * Created On: 22 Aug 2021 + * License: MIT + */ + +#ifndef KNNCPP_H_ +#define KNNCPP_H_ + +#include +#include +#include +#include + +#ifdef KNNCPP_FLANN + +#include + +#endif + +namespace knncpp +{ + /******************************************************** + * Matrix Definitions + *******************************************************/ + + typedef typename Eigen::MatrixXd::Index Index; + + typedef Eigen::Matrix Vectori; + typedef Eigen::Matrix Vector2i; + typedef Eigen::Matrix Vector3i; + typedef Eigen::Matrix Vector4i; + typedef Eigen::Matrix Vector5i; + + typedef Eigen::Matrix Matrixi; + typedef Eigen::Matrix Matrix2i; + typedef Eigen::Matrix Matrix3i; + typedef Eigen::Matrix Matrix4i; + typedef Eigen::Matrix Matrix5i; + + typedef Eigen::Matrix Matrixf; + typedef Eigen::Matrix Matrixd; + + /******************************************************** + * Distance Functors + *******************************************************/ + + /** Manhatten distance functor. + * This the same as the L1 minkowski distance but more efficient. + * @see EuclideanDistance, ChebyshevDistance, MinkowskiDistance */ + template + struct ManhattenDistance + { + /** Compute the unrooted distance between two vectors. + * @param lhs vector on left hand side + * @param rhs vector on right hand side */ + template + Scalar operator()(const Eigen::MatrixBase &lhs, + const Eigen::MatrixBase &rhs) const + { + static_assert( + std::is_same::Scalar,Scalar>::value, + "distance scalar and input matrix A must have same type"); + static_assert( + std::is_same::Scalar, Scalar>::value, + "distance scalar and input matrix B must have same type"); + + return (lhs - rhs).cwiseAbs().sum(); + } + + /** Compute the unrooted distance between two scalars. + * @param lhs scalar on left hand side + * @param rhs scalar on right hand side */ + Scalar operator()(const Scalar lhs, + const Scalar rhs) const + { + return std::abs(lhs - rhs); + } + + /** Compute the root of a unrooted distance value. + * @param value unrooted distance value */ + Scalar operator()(const Scalar val) const + { + return val; + } + }; + + /** Euclidean distance functor. + * This the same as the L2 minkowski distance but more efficient. + * @see ManhattenDistance, ChebyshevDistance, MinkowskiDistance */ + template + struct EuclideanDistance + { + /** Compute the unrooted distance between two vectors. + * @param lhs vector on left hand side + * @param rhs vector on right hand side */ + template + Scalar operator()(const Eigen::MatrixBase &lhs, + const Eigen::MatrixBase &rhs) const + { + static_assert( + std::is_same::Scalar,Scalar>::value, + "distance scalar and input matrix A must have same type"); + static_assert( + std::is_same::Scalar, Scalar>::value, + "distance scalar and input matrix B must have same type"); + + return (lhs - rhs).cwiseAbs2().sum(); + } + + /** Compute the unrooted distance between two scalars. + * @param lhs scalar on left hand side + * @param rhs scalar on right hand side */ + Scalar operator()(const Scalar lhs, + const Scalar rhs) const + { + Scalar diff = lhs - rhs; + return diff * diff; + } + + /** Compute the root of a unrooted distance value. + * @param value unrooted distance value */ + Scalar operator()(const Scalar val) const + { + return std::sqrt(val); + } + }; + + /** General minkowski distance functor. + * The infinite version is only available through the chebyshev distance. + * @see ManhattenDistance, EuclideanDistance, ChebyshevDistance */ + template + struct MinkowskiDistance + { + struct Pow + { + Scalar operator()(const Scalar val) const + { + Scalar result = 1; + for(int i = 0; i < P; ++i) + result *= val; + return result; + } + }; + + /** Compute the unrooted distance between two vectors. + * @param lhs vector on left hand side + * @param rhs vector on right hand side */ + template + Scalar operator()(const Eigen::MatrixBase &lhs, + const Eigen::MatrixBase &rhs) const + { + static_assert( + std::is_same::Scalar,Scalar>::value, + "distance scalar and input matrix A must have same type"); + static_assert( + std::is_same::Scalar, Scalar>::value, + "distance scalar and input matrix B must have same type"); + + return (lhs - rhs).cwiseAbs().unaryExpr(MinkowskiDistance::Pow()).sum(); + } + + /** Compute the unrooted distance between two scalars. + * @param lhs scalar on left hand side + * @param rhs scalar on right hand side */ + Scalar operator()(const Scalar lhs, + const Scalar rhs) const + { + return std::pow(std::abs(lhs - rhs), P);; + } + + /** Compute the root of a unrooted distance value. + * @param value unrooted distance value */ + Scalar operator()(const Scalar val) const + { + return std::pow(val, 1 / static_cast(P)); + } + }; + + /** Chebyshev distance functor. + * This distance is the same as infinity minkowski distance. + * @see ManhattenDistance, EuclideanDistance, MinkowskiDistance */ + template + struct ChebyshevDistance + { + /** Compute the unrooted distance between two vectors. + * @param lhs vector on left hand side + * @param rhs vector on right hand side */ + template + Scalar operator()(const Eigen::MatrixBase &lhs, + const Eigen::MatrixBase &rhs) const + { + static_assert( + std::is_same::Scalar,Scalar>::value, + "distance scalar and input matrix A must have same type"); + static_assert( + std::is_same::Scalar, Scalar>::value, + "distance scalar and input matrix B must have same type"); + + return (lhs - rhs).cwiseAbs().maxCoeff(); + } + + /** Compute the unrooted distance between two scalars. + * @param lhs scalar on left hand side + * @param rhs scalar on right hand side */ + Scalar operator()(const Scalar lhs, + const Scalar rhs) const + { + return std::abs(lhs - rhs); + } + + /** Compute the root of a unrooted distance value. + * @param value unrooted distance value */ + Scalar operator()(const Scalar val) const + { + return val; + } + }; + + /** Hamming distance functor. + * The distance vectors have to be of integral type and should hold the + * information vectors as bitmasks. + * Performs a XOR operation on the vectors and counts the number of set + * ones. */ + template + struct HammingDistance + { + static_assert(std::is_integral::value, + "HammingDistance requires integral Scalar type"); + + struct XOR + { + Scalar operator()(const Scalar lhs, const Scalar rhs) const + { + return lhs ^ rhs; + } + }; + + struct BitCount + { + Scalar operator()(const Scalar lhs) const + { + Scalar copy = lhs; + Scalar result = 0; + while(copy != static_cast(0)) + { + ++result; + copy &= (copy - 1); + } + + return result; + } + }; + + /** Compute the unrooted distance between two vectors. + * @param lhs vector on left hand side + * @param rhs vector on right hand side */ + template + Scalar operator()(const Eigen::MatrixBase &lhs, + const Eigen::MatrixBase &rhs) const + { + static_assert( + std::is_same::Scalar,Scalar>::value, + "distance scalar and input matrix A must have same type"); + static_assert( + std::is_same::Scalar, Scalar>::value, + "distance scalar and input matrix B must have same type"); + + return lhs. + binaryExpr(rhs, XOR()). + unaryExpr(BitCount()). + sum(); + } + + /** Compute the unrooted distance between two scalars. + * @param lhs scalar on left hand side + * @param rhs scalar on right hand side */ + Scalar operator()(const Scalar lhs, + const Scalar rhs) const + { + BitCount cnt; + XOR xOr; + return cnt(xOr(lhs, rhs)); + } + + /** Compute the root of a unrooted distance value. + * @param value unrooted distance value */ + Scalar operator()(const Scalar value) const + { + return value; + } + }; + + /** Efficient heap structure to query nearest neighbours. */ + template + class QueryHeap + { + private: + Index *indices_ = nullptr; + Scalar *distances_ = nullptr; + size_t maxSize_ = 0; + size_t size_ = 0; + public: + /** Creates a query heap with the given index and distance memory regions. */ + QueryHeap(Index *indices, Scalar *distances, const size_t maxSize) + : indices_(indices), distances_(distances), maxSize_(maxSize) + { } + + /** Pushes a new query data set into the heap with the given + * index and distance. + * The index identifies the point for which the given distance + * was computed. + * @param idx index / ID of the query point + * @param dist distance that was computed for the query point*/ + void push(const Index idx, const Scalar dist) + { + assert(!full()); + + // add new value at the end + indices_[size_] = idx; + distances_[size_] = dist; + ++size_; + + // upheap + size_t k = size_ - 1; + size_t tmp = (k - 1) / 2; + while(k > 0 && distances_[tmp] < dist) + { + distances_[k] = distances_[tmp]; + indices_[k] = indices_[tmp]; + k = tmp; + tmp = (k - 1) / 2; + } + distances_[k] = dist; + indices_[k] = idx; + } + + /** Removes the element at the front of the heap and restores + * the heap order. */ + void pop() + { + assert(!empty()); + + // replace first element with last + --size_; + distances_[0] = distances_[size_]; + indices_[0] = indices_[size_]; + + // downheap + size_t k = 0; + size_t j; + Scalar dist = distances_[0]; + Index idx = indices_[0]; + while(2 * k + 1 < size_) + { + j = 2 * k + 1; + if(j + 1 < size_ && distances_[j+1] > distances_[j]) + ++j; + // j references now greatest child + if(dist >= distances_[j]) + break; + distances_[k] = distances_[j]; + indices_[k] = indices_[j]; + k = j; + } + distances_[k] = dist; + indices_[k] = idx; + } + + /** Returns the distance of the element in front of the heap. */ + Scalar front() const + { + assert(!empty()); + return distances_[0]; + } + + /** Determines if this query heap is full. + * The heap is considered full if its number of elements + * has reached its max size. + * @return true if the heap is full, else false */ + bool full() const + { + return size_ >= maxSize_; + } + + /** Determines if this query heap is empty. + * @return true if the heap contains no elements, else false */ + bool empty() const + { + return size_ == 0; + } + + /** Returns the number of elements within the query heap. + * @return number of elements in the heap */ + size_t size() const + { + return size_; + } + + /** Clears the query heap. */ + void clear() + { + size_ = 0; + } + + /** Sorts the elements within the heap according to + * their distance. */ + void sort() + { + size_t cnt = size_; + for(size_t i = 0; i < cnt; ++i) + { + Index idx = indices_[0]; + Scalar dist = distances_[0]; + pop(); + indices_[cnt - i - 1] = idx; + distances_[cnt - i - 1] = dist; + } + } + }; + + /** Class for performing brute force knn search. */ + template> + class BruteForce + { + public: + typedef Eigen::Matrix Matrix; + typedef Eigen::Matrix Vector; + typedef knncpp::Matrixi Matrixi; + private: + Distance distance_ = Distance(); + Matrix dataCopy_ = Matrix(); + const Matrix *data_ = nullptr; + + bool sorted_ = true; + bool takeRoot_ = true; + Index threads_ = 1; + Scalar maxDist_ = 0; + + public: + + BruteForce() = default; + + /** Constructs a brute force instance with the given data. + * @param data NxM matrix, M points of dimension N + * @param copy if true copies the data, otherwise assumes static data */ + BruteForce(const Matrix &data, const bool copy = false) + : BruteForce() + { + setData(data, copy); + } + + /** Set if the points returned by the queries should be sorted + * according to their distance to the query points. + * @param sorted sort query results */ + void setSorted(const bool sorted) + { + sorted_ = sorted; + } + + /** Set if the distances after the query should be rooted or not. + * Taking the root of the distances increases query time, but the + * function will return true distances instead of their powered + * versions. + * @param takeRoot set true if root should be taken else false */ + void setTakeRoot(const bool takeRoot) + { + takeRoot_ = takeRoot; + } + + /** Set the amount of threads that should be used for querying. + * OpenMP has to be enabled for this to work. + * @param threads amount of threads, 0 for optimal choice */ + void setThreads(const unsigned int threads) + { + threads_ = threads; + } + + /** Set the maximum distance for querying the tree. + * The search will be pruned if the maximum distance is set to any + * positive number. + * @param maxDist maximum distance, <= 0 for no limit */ + void setMaxDistance(const Scalar maxDist) + { + maxDist_ = maxDist; + } + + /** Set the data points used for this tree. + * This does not build the tree. + * @param data NxM matrix, M points of dimension N + * @param copy if true data is copied, assumes static data otherwise */ + void setData(const Matrix &data, const bool copy = false) + { + if(copy) + { + dataCopy_ = data; + data_ = &dataCopy_; + } + else + { + data_ = &data; + } + } + + void setDistance(const Distance &distance) + { + distance_ = distance; + } + + void build() + { } + + template + void query(const Eigen::MatrixBase &queryPoints, + const size_t knn, + Matrixi &indices, + Matrix &distances) const + { + if(data_ == nullptr) + throw std::runtime_error("cannot query BruteForce: data not set"); + if(data_->size() == 0) + throw std::runtime_error("cannot query BruteForce: data is empty"); + if(queryPoints.rows() != dimension()) + throw std::runtime_error("cannot query BruteForce: data and query descriptors do not have same dimension"); + + const Matrix &dataPoints = *data_; + + indices.setConstant(knn, queryPoints.cols(), -1); + distances.setConstant(knn, queryPoints.cols(), -1); + + #pragma omp parallel for num_threads(threads_) + for(Index i = 0; i < queryPoints.cols(); ++i) + { + Index *idxPoint = &indices.data()[i * knn]; + Scalar *distPoint = &distances.data()[i * knn]; + + QueryHeap heap(idxPoint, distPoint, knn); + + for(Index j = 0; j < dataPoints.cols(); ++j) + { + Scalar dist = distance_(queryPoints.col(i), dataPoints.col(j)); + + // check if point is in range if max distance was set + bool isInRange = maxDist_ <= 0 || dist <= maxDist_; + // check if this node was an improvement if heap is already full + bool isImprovement = !heap.full() || + dist < heap.front(); + if(isInRange && isImprovement) + { + if(heap.full()) + heap.pop(); + heap.push(j, dist); + } + } + + if(sorted_) + heap.sort(); + + if(takeRoot_) + { + for(size_t j = 0; j < knn; ++j) + { + if(idxPoint[j] < 0) + break; + distPoint[j] = distance_(distPoint[j]); + } + } + } + } + + /** Returns the amount of data points stored in the search index. + * @return number of data points */ + Index size() const + { + return data_ == nullptr ? 0 : data_->cols(); + } + + /** Returns the dimension of the data points in the search index. + * @return dimension of data points */ + Index dimension() const + { + return data_ == nullptr ? 0 : data_->rows(); + } + }; + + // template + // struct MeanMidpointRule + // { + // typedef Eigen::Matrix Matrix; + // typedef knncpp::Matrixi Matrixi; + + // void operator(const Matrix &data, const Matrixi &indices, Index split) + // }; + + /** Class for performing k nearest neighbour searches with minkowski distances. + * This kdtree only works reliably with the minkowski distance and its + * special cases like manhatten or euclidean distance. + * @see ManhattenDistance, EuclideanDistance, ChebyshevDistance, MinkowskiDistance*/ + template + class KDTreeMinkowski + { + public: + typedef _Scalar Scalar; + typedef _Distance Distance; + typedef Eigen::Matrix Matrix; + typedef Eigen::Matrix DataMatrix; + typedef Eigen::Matrix DataVector; + typedef knncpp::Matrixi Matrixi; + private: + typedef Eigen::Matrix Bounds; + typedef Eigen::Matrix BoundingBox; + + /** Struct representing a node in the KDTree. + * It can be either a inner node or a leaf node. */ + struct Node + { + /** Indices of data points in this leaf node. */ + Index startIdx = 0; + Index length = 0; + + /** Left child of this inner node. */ + Index left = -1; + /** Right child of this inner node. */ + Index right = -1; + /** Axis of the axis aligned splitting hyper plane. */ + Index splitaxis = -1; + /** Translation of the axis aligned splitting hyper plane. */ + Scalar splitpoint = 0; + /** Lower end of the splitpoint range */ + Scalar splitlower = 0; + /** Upper end of the splitpoint range */ + Scalar splitupper = 0; + + + Node() = default; + + /** Constructor for leaf nodes */ + Node(const Index startIdx, const Index length) + : startIdx(startIdx), length(length) + { } + + /** Constructor for inner nodes */ + Node(const Index splitaxis, const Scalar splitpoint, + const Index left, const Index right) + : left(left), right(right), + splitaxis(splitaxis), splitpoint(splitpoint) + { } + + bool isLeaf() const + { + return !hasLeft() && !hasRight(); + } + + bool isInner() const + { + return hasLeft() && hasRight(); + } + + bool hasLeft() const + { + return left >= 0; + } + + bool hasRight() const + { + return right >= 0; + } + }; + + DataMatrix dataCopy_ = DataMatrix(); + const DataMatrix *data_ = nullptr; + std::vector indices_ = std::vector(); + std::vector nodes_ = std::vector(); + + Index bucketSize_ = 16; + bool sorted_ = true; + bool compact_ = false; + bool balanced_ = false; + bool takeRoot_ = true; + Index threads_ = 0; + Scalar maxDist_ = 0; + + Distance distance_ = Distance(); + + BoundingBox bbox_ = BoundingBox(); + + Index buildLeafNode(const Index startIdx, + const Index length, + BoundingBox &bbox) + { + nodes_.push_back(Node(startIdx, length)); + calculateBoundingBox(startIdx, length, bbox); + return static_cast(nodes_.size() - 1); + } + + /** Finds the minimum and maximum values of each dimension (row) in the + * data matrix. Only respects the columns specified by the index + * vector. + * @param startIdx starting index within indices data structure to search for bounding box + * @param length length of the block of indices*/ + void calculateBoundingBox(const Index startIdx, + const Index length, + BoundingBox &bbox) const + { + assert(length > 0); + assert(startIdx >= 0); + assert(static_cast(startIdx + length) <= indices_.size()); + assert(data_->rows() == bbox.cols()); + + const DataMatrix &data = *data_; + + // initialize bounds of the bounding box + Index first = indices_[startIdx]; + for(Index i = 0; i < bbox.cols(); ++i) + { + bbox(0, i) = data(i, first); + bbox(1, i) = data(i, first); + } + + // search for min / max values in data + for(Index i = 1; i < length; ++i) + { + // retrieve data index + Index col = indices_[startIdx + i]; + assert(col >= 0 && col < data.cols()); + + // check min and max for each dimension individually + for(Index j = 0; j < data.rows(); ++j) + { + bbox(0, j) = std::min(bbox(0, j), data(j, col)); + bbox(1, j) = std::max(bbox(1, j), data(j, col)); + } + } + } + + /** Calculates the bounds (min / max values) for the given dimension and block of data. */ + void calculateBounds(const Index startIdx, + const Index length, + const Index dim, + Bounds &bounds) const + { + assert(length > 0); + assert(startIdx >= 0); + assert(static_cast(startIdx + length) <= indices_.size()); + + const DataMatrix &data = *data_; + + bounds(0) = data(dim, indices_[startIdx]); + bounds(1) = data(dim, indices_[startIdx]); + + for(Index i = 1; i < length; ++i) + { + Index col = indices_[startIdx + i]; + assert(col >= 0 && col < data.cols()); + + bounds(0) = std::min(bounds(0), data(dim, col)); + bounds(1) = std::max(bounds(1), data(dim, col)); + } + } + + void calculateSplittingMidpoint(const Index startIdx, + const Index length, + const BoundingBox &bbox, + Index &splitaxis, + Scalar &splitpoint, + Index &splitoffset) + { + const DataMatrix &data = *data_; + + // search for axis with longest distance + splitaxis = 0; + Scalar splitsize = static_cast(0); + for(Index i = 0; i < data.rows(); ++i) + { + Scalar diff = bbox(1, i) - bbox(0, i); + if(diff > splitsize) + { + splitaxis = i; + splitsize = diff; + } + } + + // calculate the bounds in this axis and update our data + // accordingly + Bounds bounds; + calculateBounds(startIdx, length, splitaxis, bounds); + splitsize = bounds(1) - bounds(0); + + const Index origSplitaxis = splitaxis; + for(Index i = 0; i < data.rows(); ++i) + { + // skip the dimension of the previously found splitaxis + if(i == origSplitaxis) + continue; + Scalar diff = bbox(1, i) - bbox(0, i); + // check if the split for this dimension would be potentially larger + if(diff > splitsize) + { + Bounds newBounds; + // update the bounds to their actual current value + calculateBounds(startIdx, length, splitaxis, newBounds); + diff = newBounds(1) - newBounds(0); + if(diff > splitsize) + { + splitaxis = i; + splitsize = diff; + bounds = newBounds; + } + } + } + + // use the sliding midpoint rule + splitpoint = (bounds(0) + bounds(1)) / static_cast(2); + + Index leftIdx = startIdx; + Index rightIdx = startIdx + length - 1; + + // first loop checks left < splitpoint and right >= splitpoint + while(leftIdx <= rightIdx) + { + // increment left as long as left has not reached right and + // the value of the left element is less than the splitpoint + while(leftIdx <= rightIdx && data(splitaxis, indices_[leftIdx]) < splitpoint) + ++leftIdx; + + // decrement right as long as left has not reached right and + // the value of the right element is greater than the splitpoint + while(leftIdx <= rightIdx && data(splitaxis, indices_[rightIdx]) >= splitpoint) + --rightIdx; + + if(leftIdx <= rightIdx) + { + std::swap(indices_[leftIdx], indices_[rightIdx]); + ++leftIdx; + --rightIdx; + } + } + + // remember this offset from starting index + const Index offset1 = leftIdx - startIdx; + + rightIdx = startIdx + length - 1; + // second loop checks left <= splitpoint and right > splitpoint + while(leftIdx <= rightIdx) + { + // increment left as long as left has not reached right and + // the value of the left element is less than the splitpoint + while(leftIdx <= rightIdx && data(splitaxis, indices_[leftIdx]) <= splitpoint) + ++leftIdx; + + // decrement right as long as left has not reached right and + // the value of the right element is greater than the splitpoint + while(leftIdx <= rightIdx && data(splitaxis, indices_[rightIdx]) > splitpoint) + --rightIdx; + + if(leftIdx <= rightIdx) + { + std::swap(indices_[leftIdx], indices_[rightIdx]); + ++leftIdx; + --rightIdx; + } + } + + // remember this offset from starting index + const Index offset2 = leftIdx - startIdx; + + const Index halfLength = length / static_cast(2); + + // find a separation of points such that is best balanced + // offset1 denotes separation where equal points are all on the right + // offset2 denots separation where equal points are all on the left + if (offset1 > halfLength) + splitoffset = offset1; + else if (offset2 < halfLength) + splitoffset = offset2; + // when we get here offset1 < halflength and offset2 > halflength + // so simply split the equal elements in the middle + else + splitoffset = halfLength; + } + + Index buildInnerNode(const Index startIdx, + const Index length, + BoundingBox &bbox) + { + assert(length > 0); + assert(startIdx >= 0); + assert(static_cast(startIdx + length) <= indices_.size()); + assert(data_->rows() == bbox.cols()); + + // create node + const Index nodeIdx = nodes_.size(); + nodes_.push_back(Node()); + + Index splitaxis; + Index splitoffset; + Scalar splitpoint; + calculateSplittingMidpoint(startIdx, length, bbox, splitaxis, splitpoint, splitoffset); + + nodes_[nodeIdx].splitaxis = splitaxis; + nodes_[nodeIdx].splitpoint = splitpoint; + + const Index leftStart = startIdx; + const Index leftLength = splitoffset; + const Index rightStart = startIdx + splitoffset; + const Index rightLength = length - splitoffset; + + BoundingBox bboxLeft = bbox; + BoundingBox bboxRight = bbox; + + // do left build + bboxLeft(1, splitaxis) = splitpoint; + Index left = buildR(leftStart, leftLength, bboxLeft); + nodes_[nodeIdx].left = left; + + // do right build + bboxRight(0, splitaxis) = splitpoint; + Index right = buildR(rightStart, rightLength, bboxRight); + nodes_[nodeIdx].right = right; + + // extract the range of the splitpoint + nodes_[nodeIdx].splitlower = bboxLeft(1, splitaxis); + nodes_[nodeIdx].splitupper = bboxRight(0, splitaxis); + + // update the bounding box to the values of the new bounding boxes + for(Index i = 0; i < bbox.cols(); ++i) + { + bbox(0, i) = std::min(bboxLeft(0, i), bboxRight(0, i)); + bbox(1, i) = std::max(bboxLeft(1, i), bboxRight(1, i)); + } + + return nodeIdx; + } + + Index buildR(const Index startIdx, + const Index length, + BoundingBox &bbox) + { + // check for base case + if(length <= bucketSize_) + return buildLeafNode(startIdx, length, bbox); + else + return buildInnerNode(startIdx, length, bbox); + } + + bool isDistanceInRange(const Scalar dist) const + { + return maxDist_ <= 0 || dist <= maxDist_; + } + + bool isDistanceImprovement(const Scalar dist, const QueryHeap &dataHeap) const + { + return !dataHeap.full() || dist < dataHeap.front(); + } + + template + void queryLeafNode(const Node &node, + const Eigen::MatrixBase &queryPoint, + QueryHeap &dataHeap) const + { + assert(node.isLeaf()); + + const DataMatrix &data = *data_; + + // go through all points in this leaf node and do brute force search + for(Index i = 0; i < node.length; ++i) + { + const Index idx = node.startIdx + i; + assert(idx >= 0 && idx < static_cast(indices_.size())); + + // retrieve index of the current data point + const Index dataIdx = indices_[idx]; + const Scalar dist = distance_(queryPoint, data.col(dataIdx)); + + // check if point is within max distance and if the value would be + // an improvement + if(isDistanceInRange(dist) && isDistanceImprovement(dist, dataHeap)) + { + if(dataHeap.full()) + dataHeap.pop(); + dataHeap.push(dataIdx, dist); + } + } + } + + template + void queryInnerNode(const Node &node, + const Eigen::MatrixBase &queryPoint, + QueryHeap &dataHeap, + DataVector &splitdists, + const Scalar mindist) const + { + assert(node.isInner()); + + const Index splitaxis = node.splitaxis; + const Scalar splitval = queryPoint(splitaxis, 0); + Scalar splitdist; + Index firstNode; + Index secondNode; + // check if right or left child should be visited + const bool visitLeft = (splitval - node.splitlower + splitval - node.splitupper) < 0; + if(visitLeft) + { + firstNode = node.left; + secondNode = node.right; + splitdist = distance_(splitval, node.splitupper); + } + else + { + firstNode = node.right; + secondNode = node.left; + splitdist = distance_(splitval, node.splitlower); + } + + queryR(nodes_[firstNode], queryPoint, dataHeap, splitdists, mindist); + + const Scalar mindistNew = mindist + splitdist - splitdists(splitaxis); + + // check if node is in range if max distance was set + // check if this node was an improvement if heap is already full + if(isDistanceInRange(mindistNew) && isDistanceImprovement(mindistNew, dataHeap)) + { + const Scalar splitdistOld = splitdists(splitaxis); + splitdists(splitaxis) = splitdist; + queryR(nodes_[secondNode], queryPoint, dataHeap, splitdists, mindistNew); + splitdists(splitaxis) = splitdistOld; + } + } + + template + void queryR(const Node &node, + const Eigen::MatrixBase &queryPoint, + QueryHeap &dataHeap, + DataVector &splitdists, + const Scalar mindist) const + { + if(node.isLeaf()) + queryLeafNode(node, queryPoint, dataHeap); + else + queryInnerNode(node, queryPoint, dataHeap, splitdists, mindist); + } + + /** Recursively computes the depth for the given node. */ + Index depthR(const Node &node) const + { + if(node.isLeaf()) + return 1; + else + { + Index left = depthR(nodes_[node.left]); + Index right = depthR(nodes_[node.right]); + return std::max(left, right) + 1; + } + } + + public: + + /** Constructs an empty KDTree. */ + KDTreeMinkowski() + { } + + /** Constructs KDTree with the given data. This does not build the + * the index of the tree. + * @param data NxM matrix, M points of dimension N + * @param copy if true copies the data, otherwise assumes static data */ + KDTreeMinkowski(const DataMatrix &data, const bool copy=false) + { + setData(data, copy); + } + + /** Set the maximum amount of data points per leaf in the tree (aka + * bucket size). + * @param bucketSize amount of points per leaf. */ + void setBucketSize(const Index bucketSize) + { + bucketSize_ = bucketSize; + } + + /** Set if the points returned by the queries should be sorted + * according to their distance to the query points. + * @param sorted sort query results */ + void setSorted(const bool sorted) + { + sorted_ = sorted; + } + + /** Set if the tree should be built as balanced as possible. + * This increases build time, but decreases search time. + * @param balanced set true to build a balanced tree */ + void setBalanced(const bool balanced) + { + balanced_ = balanced; + } + + /** Set if the distances after the query should be rooted or not. + * Taking the root of the distances increases query time, but the + * function will return true distances instead of their powered + * versions. + * @param takeRoot set true if root should be taken else false */ + void setTakeRoot(const bool takeRoot) + { + takeRoot_ = takeRoot; + } + + /** Set if the tree should be built with compact leaf nodes. + * This increases build time, but makes leaf nodes denser (more) + * points. Thus less visits are necessary. + * @param compact set true ti build a tree with compact leafs */ + void setCompact(const bool compact) + { + compact_ = compact; + } + + /** Set the amount of threads that should be used for building and + * querying the tree. + * OpenMP has to be enabled for this to work. + * @param threads amount of threads, 0 for optimal choice */ + void setThreads(const unsigned int threads) + { + threads_ = threads; + } + + /** Set the maximum distance for querying the tree. + * The search will be pruned if the maximum distance is set to any + * positive number. + * @param maxDist maximum distance, <= 0 for no limit */ + void setMaxDistance(const Scalar maxDist) + { + maxDist_ = maxDist; + } + + /** Set the data points used for this tree. + * This does not build the tree. + * @param data NxM matrix, M points of dimension N + * @param copy if true data is copied, assumes static data otherwise */ + void setData(const DataMatrix &data, const bool copy = false) + { + clear(); + if(copy) + { + dataCopy_ = data; + data_ = &dataCopy_; + } + else + { + data_ = &data; + } + } + + void setDistance(const Distance &distance) + { + distance_ = distance; + } + + /** Builds the search index of the tree. + * Data has to be set and must be non-empty. */ + void build() + { + if(data_ == nullptr) + throw std::runtime_error("cannot build KDTree; data not set"); + + if(data_->size() == 0) + throw std::runtime_error("cannot build KDTree; data is empty"); + + clear(); + nodes_.reserve((data_->cols() / bucketSize_) + 1); + + // initialize indices in simple sequence + indices_.resize(data_->cols()); + for(size_t i = 0; i < indices_.size(); ++i) + indices_[i] = i; + + bbox_.resize(2, data_->rows()); + Index startIdx = 0; + Index length = data_->cols(); + + calculateBoundingBox(startIdx, length, bbox_); + + buildR(startIdx, length, bbox_); + } + + /** Queries the tree for the nearest neighbours of the given query + * points. + * + * The tree has to be built before it can be queried. + * + * The query points have to have the same dimension as the data points + * of the tree. + * + * The result matrices will be resized appropriatley. + * Indices and distances will be set to -1 if less than knn neighbours + * were found. + * + * @param queryPoints NxM matrix, M points of dimension N + * @param knn amount of neighbours to be found + * @param indices KNNxM matrix, indices of neighbours in the data set + * @param distances KNNxM matrix, distance between query points and + * neighbours */ + template + void query(const Eigen::MatrixBase &queryPoints, + const size_t knn, + Matrixi &indices, + Matrix &distances) const + { + if(nodes_.size() == 0) + throw std::runtime_error("cannot query KDTree; not built yet"); + + if(queryPoints.rows() != dimension()) + throw std::runtime_error("cannot query KDTree; data and query points do not have same dimension"); + + distances.setConstant(knn, queryPoints.cols(), -1); + indices.setConstant(knn, queryPoints.cols(), -1); + + Index *indicesRaw = indices.data(); + Scalar *distsRaw = distances.data(); + + #pragma omp parallel for num_threads(threads_) + for(Index i = 0; i < queryPoints.cols(); ++i) + { + + Scalar *distPoint = &distsRaw[i * knn]; + Index *idxPoint = &indicesRaw[i * knn]; + + // create heap to find nearest neighbours + QueryHeap dataHeap(idxPoint, distPoint, knn); + + Scalar mindist = static_cast(0); + DataVector splitdists(queryPoints.rows()); + + for(Index j = 0; j < splitdists.rows(); ++j) + { + const Scalar value = queryPoints(j, i); + const Scalar lower = bbox_(0, j); + const Scalar upper = bbox_(1, j); + if(value < lower) + { + splitdists(j) = distance_(value, lower); + } + else if(value > upper) + { + splitdists(j) = distance_(value, upper); + } + else + { + splitdists(j) = static_cast(0); + } + + mindist += splitdists(j); + } + + queryR(nodes_[0], queryPoints.col(i), dataHeap, splitdists, mindist); + + if(sorted_) + dataHeap.sort(); + + if(takeRoot_) + { + for(size_t j = 0; j < knn; ++j) + { + if(distPoint[j] < 0) + break; + distPoint[j] = distance_(distPoint[j]); + } + } + } + } + + /** Clears the tree. */ + void clear() + { + nodes_.clear(); + } + + /** Returns the amount of data points stored in the search index. + * @return number of data points */ + Index size() const + { + return data_ == nullptr ? 0 : data_->cols(); + } + + /** Returns the dimension of the data points in the search index. + * @return dimension of data points */ + Index dimension() const + { + return data_ == nullptr ? 0 : data_->rows(); + } + + /** Returns the maxximum depth of the tree. + * @return maximum depth of the tree */ + Index depth() const + { + return nodes_.size() == 0 ? 0 : depthR(nodes_.front()); + } + }; + + template> using KDTreeMinkowski2 = KDTreeMinkowski<_Scalar, 2, _Distance>; + template> using KDTreeMinkowski3 = KDTreeMinkowski<_Scalar, 3, _Distance>; + template> using KDTreeMinkowski4 = KDTreeMinkowski<_Scalar, 4, _Distance>; + template> using KDTreeMinkowski5 = KDTreeMinkowski<_Scalar, 5, _Distance>; + template> using KDTreeMinkowskiX = KDTreeMinkowski<_Scalar, Eigen::Dynamic, _Distance>; + + /** Class for performing KNN search in hamming space by multi-index hashing. */ + template + class MultiIndexHashing + { + public: + static_assert(std::is_integral::value, "MultiIndexHashing Scalar has to be integral"); + + typedef Eigen::Matrix Matrix; + typedef Eigen::Matrix Vector; + typedef knncpp::Matrixi Matrixi; + + private: + HammingDistance distance_; + + Matrix dataCopy_; + const Matrix *data_; + + bool sorted_; + Scalar maxDist_; + Index substrLen_; + Index threads_; + std::vector>> buckets_; + + template + Scalar extractCode(const Eigen::MatrixBase &data, + const Index idx, + const Index offset) const + { + Index leftShift = std::max(0, static_cast(sizeof(Scalar)) - offset - substrLen_); + Index rightShift = leftShift + offset; + + Scalar code = (data(idx, 0) << (leftShift * 8)) >> (rightShift * 8); + + if(static_cast(sizeof(Scalar)) - offset < substrLen_ && idx + 1 < data.rows()) + { + Index shift = 2 * static_cast(sizeof(Scalar)) - substrLen_ - offset; + code |= data(idx+1, 0) << (shift * 8); + } + + return code; + } + public: + MultiIndexHashing() + : distance_(), dataCopy_(), data_(nullptr), sorted_(true), + maxDist_(0), substrLen_(1), threads_(1) + { } + + /** Constructs an index with the given data. + * This does not build the the index. + * @param data NxM matrix, M points of dimension N + * @param copy if true copies the data, otherwise assumes static data */ + MultiIndexHashing(const Matrix &data, const bool copy=false) + : MultiIndexHashing() + { + setData(data, copy); + } + + /** Set the maximum distance for querying the index. + * Note that if no maximum distance is used, this algorithm performs + * basically a brute force search. + * @param maxDist maximum distance, <= 0 for no limit */ + void setMaxDistance(const Scalar maxDist) + { + maxDist_ = maxDist; + } + + /** Set if the points returned by the queries should be sorted + * according to their distance to the query points. + * @param sorted sort query results */ + void setSorted(const bool sorted) + { + sorted_ = sorted; + } + + /** Set the amount of threads that should be used for building and + * querying the tree. + * OpenMP has to be enabled for this to work. + * @param threads amount of threads, 0 for optimal choice */ + void setThreads(const unsigned int threads) + { + threads_ = threads; + } + + /** Set the length of substrings (in bytes) used for multi index hashing. + * @param len lentth of bucket substrings in bytes*/ + void setSubstringLength(const Index len) + { + substrLen_ = len; + } + + /** Set the data points used for the KNN search. + * @param data NxM matrix, M points of dimension N + * @param copy if true data is copied, assumes static data otherwise */ + void setData(const Matrix &data, const bool copy = false) + { + clear(); + if(copy) + { + dataCopy_ = data; + data_ = &dataCopy_; + } + else + { + data_ = &data; + } + } + + void build() + { + if(data_ == nullptr) + throw std::runtime_error("cannot build MultiIndexHashing; data not set"); + if(data_->size() == 0) + throw std::runtime_error("cannot build MultiIndexHashing; data is empty"); + + const Matrix &data = *data_; + const Index bytesPerVec = data.rows() * static_cast(sizeof(Scalar)); + if(bytesPerVec % substrLen_ != 0) + throw std::runtime_error("cannot build MultiIndexHashing; cannot divide byte count per vector by substring length without remainings"); + + buckets_.clear(); + buckets_.resize(bytesPerVec / substrLen_); + + for(size_t i = 0; i < buckets_.size(); ++i) + { + Index start = static_cast(i) * substrLen_; + Index idx = start / static_cast(sizeof(Scalar)); + Index offset = start % static_cast(sizeof(Scalar)); + std::map> &map = buckets_[i]; + + for(Index c = 0; c < data.cols(); ++c) + { + Scalar code = extractCode(data.col(c), idx, offset); + if(map.find(code) == map.end()) + map[code] = std::vector(); + map[code].push_back(c); + } + } + } + + template + void query(const Eigen::MatrixBase &queryPoints, + const size_t knn, + Matrixi &indices, + Matrix &distances) const + { + if(buckets_.size() == 0) + throw std::runtime_error("cannot query MultiIndexHashing; not built yet"); + if(queryPoints.rows() != dimension()) + throw std::runtime_error("cannot query MultiIndexHashing; data and query points do not have same dimension"); + + const Matrix &data = *data_; + + indices.setConstant(knn, queryPoints.cols(), -1); + distances.setConstant(knn, queryPoints.cols(), -1); + + Index *indicesRaw = indices.data(); + Scalar *distsRaw = distances.data(); + + Scalar maxDistPart = maxDist_ / buckets_.size(); + + #pragma omp parallel for num_threads(threads_) + for(Index c = 0; c < queryPoints.cols(); ++c) + { + std::set candidates; + for(size_t i = 0; i < buckets_.size(); ++i) + { + Index start = static_cast(i) * substrLen_; + Index idx = start / static_cast(sizeof(Scalar)); + Index offset = start % static_cast(sizeof(Scalar)); + const std::map> &map = buckets_[i]; + + Scalar code = extractCode(queryPoints.col(c), idx, offset); + for(const auto &x: map) + { + Scalar dist = distance_(x.first, code); + if(maxDistPart <= 0 || dist <= maxDistPart) + { + for(size_t j = 0; j < x.second.size(); ++j) + candidates.insert(x.second[j]); + } + } + } + + Scalar *distPoint = &distsRaw[c * knn]; + Index *idxPoint = &indicesRaw[c * knn]; + // create heap to find nearest neighbours + QueryHeap dataHeap(idxPoint, distPoint, knn); + + for(Index idx: candidates) + { + Scalar dist = distance_(data.col(idx), queryPoints.col(c)); + + bool isInRange = maxDist_ <= 0 || dist <= maxDist_; + bool isImprovement = !dataHeap.full() || + dist < dataHeap.front(); + if(isInRange && isImprovement) + { + if(dataHeap.full()) + dataHeap.pop(); + dataHeap.push(idx, dist); + } + } + + if(sorted_) + dataHeap.sort(); + } + } + + /** Returns the amount of data points stored in the search index. + * @return number of data points */ + Index size() const + { + return data_ == nullptr ? 0 : data_->cols(); + } + + /** Returns the dimension of the data points in the search index. + * @return dimension of data points */ + Index dimension() const + { + return data_ == nullptr ? 0 : data_->rows(); + } + + void clear() + { + data_ = nullptr; + dataCopy_.resize(0, 0); + buckets_.clear(); + } + + }; + + #ifdef KNNCPP_FLANN + + /** Wrapper class of FLANN kdtrees for the use with Eigen3. */ + template> + class KDTreeFlann + { + public: + typedef Eigen::Matrix Matrix; + typedef Eigen::Matrix Vector; + typedef Eigen::Matrix Matrixi; + + private: + typedef flann::Index FlannIndex; + + Matrix dataCopy_; + Matrix *dataPoints_; + + FlannIndex *index_; + flann::SearchParams searchParams_; + flann::IndexParams indexParams_; + Scalar maxDist_; + + public: + KDTreeFlann() + : dataCopy_(), dataPoints_(nullptr), index_(nullptr), + searchParams_(32, 0, false), + indexParams_(flann::KDTreeSingleIndexParams(15)), + maxDist_(0) + { + } + + KDTreeFlann(Matrix &data, const bool copy = false) + : KDTreeFlann() + { + setData(data, copy); + } + + ~KDTreeFlann() + { + clear(); + } + + void setIndexParams(const flann::IndexParams ¶ms) + { + indexParams_ = params; + } + + void setChecks(const int checks) + { + searchParams_.checks = checks; + } + + void setSorted(const bool sorted) + { + searchParams_.sorted = sorted; + } + + void setThreads(const int threads) + { + searchParams_.cores = threads; + } + + void setEpsilon(const float eps) + { + searchParams_.eps = eps; + } + + void setMaxDistance(const Scalar dist) + { + maxDist_ = dist; + } + + void setData(Matrix &data, const bool copy = false) + { + if(copy) + { + dataCopy_ = data; + dataPoints_ = &dataCopy_; + } + else + { + dataPoints_ = &data; + } + + clear(); + } + + void build() + { + if(dataPoints_ == nullptr) + throw std::runtime_error("cannot build KDTree; data not set"); + if(dataPoints_->size() == 0) + throw std::runtime_error("cannot build KDTree; data is empty"); + + if(index_ != nullptr) + delete index_; + + flann::Matrix dataPts( + dataPoints_->data(), + dataPoints_->cols(), + dataPoints_->rows()); + + index_ = new FlannIndex(dataPts, indexParams_); + index_->buildIndex(); + } + + void query(Matrix &queryPoints, + const size_t knn, + Matrixi &indices, + Matrix &distances) const + { + if(index_ == nullptr) + throw std::runtime_error("cannot query KDTree; not built yet"); + if(dataPoints_->rows() != queryPoints.rows()) + throw std::runtime_error("cannot query KDTree; KDTree has different dimension than query data"); + + // resize result matrices + distances.resize(knn, queryPoints.cols()); + indices.resize(knn, queryPoints.cols()); + + // wrap matrices into flann matrices + flann::Matrix queryPts( + queryPoints.data(), + queryPoints.cols(), + queryPoints.rows()); + flann::Matrix indicesF( + indices.data(), + indices.cols(), + indices.rows()); + flann::Matrix distancesF( + distances.data(), + distances.cols(), + distances.rows()); + + // if maximum distance was set then use radius search + if(maxDist_ > 0) + index_->radiusSearch(queryPts, indicesF, distancesF, maxDist_, searchParams_); + else + index_->knnSearch(queryPts, indicesF, distancesF, knn, searchParams_); + + // make result matrices compatible to API + #pragma omp parallel for num_threads(searchParams_.cores) + for(Index i = 0; i < indices.cols(); ++i) + { + bool found = false; + for(Index j = 0; j < indices.rows(); ++j) + { + if(indices(j, i) == -1) + found = true; + + if(found) + { + indices(j, i) = -1; + distances(j, i) = -1; + } + } + } + } + + Index size() const + { + return dataPoints_ == nullptr ? 0 : dataPoints_->cols(); + } + + Index dimension() const + { + return dataPoints_ == nullptr ? 0 : dataPoints_->rows(); + } + + void clear() + { + if(index_ != nullptr) + { + delete index_; + index_ = nullptr; + } + } + + FlannIndex &flannIndex() + { + return index_; + } + }; + + typedef KDTreeFlann KDTreeFlannd; + typedef KDTreeFlann KDTreeFlannf; + + #endif +} + +#endif \ No newline at end of file diff --git a/src/nng.cpp b/src/nng.cpp new file mode 100644 index 0000000..a326414 --- /dev/null +++ b/src/nng.cpp @@ -0,0 +1,65 @@ +#include +#include +#include +#include "knncpp.h" + +using namespace Rcpp; + +// [[Rcpp::depends(RcppEigen)]] +// [[Rcpp::export]] +List findNeighbors(NumericMatrix data, int k, bool mutual) { + int n = data.nrow(), + d = data.ncol(); + + Eigen::MatrixXd dataPoints(d, n); + for (int row = 0; row < n; ++row) { + for (int col = 0; col < d; ++col) { + dataPoints(col,row) = data(row,col); //dataPoints: by columns + } + } + + knncpp::KDTreeMinkowskiX> kdtree(dataPoints); + kdtree.setBucketSize(16); + kdtree.setSorted(false); + kdtree.setTakeRoot(false); + kdtree.setMaxDistance(0); + kdtree.setThreads(0); + kdtree.build(); + + knncpp::Matrixi indices; + Eigen::MatrixXd distances; + // k+1 because i is always a neighbor of i (to discard) + kdtree.query(dataPoints, k+1, indices, distances); + + NumericVector res_edges(0); + NumericVector res_dists(0); + for (int i = 0; i <= k; ++i) { + for (int j = 0; j < n; ++j) { + if (indices(i,j) == j) + continue; + bool addRow = false; + if (!mutual) + addRow = true; + else if (mutual && j < indices(i,j)) { + int l = 0; + for (; l <= k; ++l) { + if (indices(l,indices(i,j)) == j) + break; + } + if (l <= k) + addRow = true; + } + if (addRow) { + // R indices from 1 to n: + res_edges.push_back(j+1); + res_edges.push_back(indices(i,j)+1); + res_dists.push_back(distances(i,j)); + } + } + } + + res_edges.attr("dim") = Dimension(2, res_edges.length() / 2); + List L = List::create(Named("edges") = res_edges, + Named("euc_dists") = res_dists); + return L; +}