151 lines
5.0 KiB
C++
151 lines
5.0 KiB
C++
/*
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----
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This file is part of SECONDO.
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Copyright (C) 2021, University in Hagen, Department of Computer Science,
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Database Systems for New Applications.
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SECONDO is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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SECONDO is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with SECONDO; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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----
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//paragraph [1] Title: [{\Large \bf \begin {center}] [\end {center}}]
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//[TOC] [\tableofcontents]
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//[ue] [\"u]
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//[ae] [\"a]
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//[oe] [\"o]
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//[x] [$\times $]
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//[->] [$\rightarrow $]
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//[pow] [\verb+^+]
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[1] Association Analysis Algebra Implementation
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January 2021 - April 2021, P. Fedorow for bachelor thesis.
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*/
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#pragma once
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#include "Algebras/Collection/IntSet.h"
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#include "Algebras/Relation-C++/RelationAlgebra.h" // rel, trel, tuple
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#include "NestedList.h"
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#include "Operator.h"
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#include <functional>
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#include <set>
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#include <utility>
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#include <vector>
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namespace AssociationAnalysis {
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namespace {
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// Implementation of a hash tree as described by Agrawal et al. in Fast
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// Algorithms for Mining Association Rules.
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//
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// It is used to accelerate the support-counting of the candidate itemsets by
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// providing a subset of all candidates to test against a given transaction.
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class ItemsetHashTree {
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public:
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ItemsetHashTree() : nodes(1) {}
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// Inserts the itemset into the hash tree. All inserted itemsets have to be of
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// the same size.
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void insert(const std::vector<int> &itemset);
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// Returns all itemsets that potentially can be part of the given transaction.
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[[nodiscard]] std::vector<std::reference_wrapper<const std::vector<int>>>
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subset(const collection::IntSet *transaction) const;
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// Returns true if the hash-tree is empty.
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[[nodiscard]] bool empty() const;
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private:
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// Specifies how many itemsets a node can hold before it is broken up.
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static const std::size_t ITEMSET_THRESHOLD = 32;
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// Specifies how many children-nodes there are per interior node.
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static const std::size_t CHILDREN_NUM = 128;
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void insert(const std::vector<int> &itemset, std::size_t node,
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std::size_t depth);
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void subset(const collection::IntSet *transaction, std::size_t node,
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std::size_t depth,
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std::vector<std::reference_wrapper<const std::vector<int>>>
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&itemsets) const;
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struct Node {
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Node() : isLeaf(true), itemsets(), children() {}
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bool isLeaf;
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// If the node is a leaf node than the itemsets are stored here.
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std::vector<std::vector<int>> itemsets;
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// If the node is an interior node than the indexes of the children nodes
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// are stored here.
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std::vector<std::size_t> children;
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};
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// Nodes are stored in a vector and point to each other by using indexes into
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// the same vector.
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std::vector<Node> nodes;
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};
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} // namespace
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// Local info class for the apriori operator. Contains the implementation of the
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// apriori-algorithm.
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class aprioriLI {
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public:
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// Finds all frequent itemsets that satisfy the support given by minSupport.
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// The itemset of a transaction is extracted from each tuple of the relation
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// by an index given by itemsetAttr.
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aprioriLI(GenericRelation *relation, int minSupport, int itemsetAttr,
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int deoptimize);
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~aprioriLI() { this->tupleType->DeleteIfAllowed(); }
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// Returns the next frequent itemset as a tuple.
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Tuple *getNext();
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private:
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// Used to generate a stream of the frequent itemsets.
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std::vector<std::pair<std::vector<int>, double>>::const_iterator it;
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// Contains the frequent itemsets annotated by their support.
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std::vector<std::pair<std::vector<int>, double>> frequentItemsets;
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// Describes the resulting tuple type: tuple(Itemset: intset, Support: real).
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TupleType *tupleType;
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};
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// Operator info for the apriori operator.
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struct aprioriInfo : OperatorInfo {
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aprioriInfo() : OperatorInfo() {
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this->name = "apriori";
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this->signature = "rel(tuple(...)) attr real -> stream(tuple(Itemset: "
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"intset, Support: real))";
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this->appendSignature("rel(tuple(...)) attr int -> stream(tuple(Itemset: "
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"intset, Support: real))");
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this->syntax = "_ apriori[_, _]";
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this->meaning = "Discovers the frequent itemsets in the given relation of "
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"transactions by using the apriori-algorithm. The expected "
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"arguments are: the relation that contains the "
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"transactions, the name of the attribute that contains the "
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"items as an intset and the minimum support to look for.";
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this->usesArgsInTypeMapping = true;
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}
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};
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} // namespace AssociationAnalysis
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