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+//===-- HeuristicSolver.h - Heuristic PBQP Solver --------------*- C++ --*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Heuristic PBQP solver. This solver is able to perform optimal reductions for
+// nodes of degree 0, 1 or 2. For nodes of degree >2 a plugable heuristic is
+// used to to select a node for reduction.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_PBQP_HEURISTICSOLVER_H
+#define LLVM_CODEGEN_PBQP_HEURISTICSOLVER_H
+
+#include "Solver.h"
+#include "AnnotatedGraph.h"
+#include "llvm/Support/raw_ostream.h"
+#include <limits>
+
+namespace PBQP {
+
+/// \brief Important types for the HeuristicSolverImpl.
+///
+/// Declared seperately to allow access to heuristic classes before the solver
+/// is fully constructed.
+template <typename HeuristicNodeData, typename HeuristicEdgeData>
+class HSITypes {
+public:
+
+ class NodeData;
+ class EdgeData;
+
+ typedef AnnotatedGraph<NodeData, EdgeData> SolverGraph;
+ typedef typename SolverGraph::NodeIterator GraphNodeIterator;
+ typedef typename SolverGraph::EdgeIterator GraphEdgeIterator;
+ typedef typename SolverGraph::AdjEdgeIterator GraphAdjEdgeIterator;
+
+ typedef std::list<GraphNodeIterator> NodeList;
+ typedef typename NodeList::iterator NodeListIterator;
+
+ typedef std::vector<GraphNodeIterator> NodeStack;
+ typedef typename NodeStack::iterator NodeStackIterator;
+
+ class NodeData {
+ friend class EdgeData;
+
+ private:
+
+ typedef std::list<GraphEdgeIterator> LinksList;
+
+ unsigned numLinks;
+ LinksList links, solvedLinks;
+ NodeListIterator bucketItr;
+ HeuristicNodeData heuristicData;
+
+ public:
+
+ typedef typename LinksList::iterator AdjLinkIterator;
+
+ private:
+
+ AdjLinkIterator addLink(const GraphEdgeIterator &edgeItr) {
+ ++numLinks;
+ return links.insert(links.end(), edgeItr);
+ }
+
+ void delLink(const AdjLinkIterator &adjLinkItr) {
+ --numLinks;
+ links.erase(adjLinkItr);
+ }
+
+ public:
+
+ NodeData() : numLinks(0) {}
+
+ unsigned getLinkDegree() const { return numLinks; }
+
+ HeuristicNodeData& getHeuristicData() { return heuristicData; }
+ const HeuristicNodeData& getHeuristicData() const {
+ return heuristicData;
+ }
+
+ void setBucketItr(const NodeListIterator &bucketItr) {
+ this->bucketItr = bucketItr;
+ }
+
+ const NodeListIterator& getBucketItr() const {
+ return bucketItr;
+ }
+
+ AdjLinkIterator adjLinksBegin() {
+ return links.begin();
+ }
+
+ AdjLinkIterator adjLinksEnd() {
+ return links.end();
+ }
+
+ void addSolvedLink(const GraphEdgeIterator &solvedLinkItr) {
+ solvedLinks.push_back(solvedLinkItr);
+ }
+
+ AdjLinkIterator solvedLinksBegin() {
+ return solvedLinks.begin();
+ }
+
+ AdjLinkIterator solvedLinksEnd() {
+ return solvedLinks.end();
+ }
+
+ };
+
+ class EdgeData {
+ private:
+
+ SolverGraph &g;
+ GraphNodeIterator node1Itr, node2Itr;
+ HeuristicEdgeData heuristicData;
+ typename NodeData::AdjLinkIterator node1ThisEdgeItr, node2ThisEdgeItr;
+
+ public:
+
+ EdgeData(SolverGraph &g) : g(g) {}
+
+ HeuristicEdgeData& getHeuristicData() { return heuristicData; }
+ const HeuristicEdgeData& getHeuristicData() const {
+ return heuristicData;
+ }
+
+ void setup(const GraphEdgeIterator &thisEdgeItr) {
+ node1Itr = g.getEdgeNode1Itr(thisEdgeItr);
+ node2Itr = g.getEdgeNode2Itr(thisEdgeItr);
+
+ node1ThisEdgeItr = g.getNodeData(node1Itr).addLink(thisEdgeItr);
+ node2ThisEdgeItr = g.getNodeData(node2Itr).addLink(thisEdgeItr);
+ }
+
+ void unlink() {
+ g.getNodeData(node1Itr).delLink(node1ThisEdgeItr);
+ g.getNodeData(node2Itr).delLink(node2ThisEdgeItr);
+ }
+
+ };
+
+};
+
+template <typename Heuristic>
+class HeuristicSolverImpl {
+public:
+ // Typedefs to make life easier:
+ typedef HSITypes<typename Heuristic::NodeData,
+ typename Heuristic::EdgeData> HSIT;
+ typedef typename HSIT::SolverGraph SolverGraph;
+ typedef typename HSIT::NodeData NodeData;
+ typedef typename HSIT::EdgeData EdgeData;
+ typedef typename HSIT::GraphNodeIterator GraphNodeIterator;
+ typedef typename HSIT::GraphEdgeIterator GraphEdgeIterator;
+ typedef typename HSIT::GraphAdjEdgeIterator GraphAdjEdgeIterator;
+
+ typedef typename HSIT::NodeList NodeList;
+ typedef typename HSIT::NodeListIterator NodeListIterator;
+
+ typedef std::vector<GraphNodeIterator> NodeStack;
+ typedef typename NodeStack::iterator NodeStackIterator;
+
+ /// \brief Constructor, which performs all the actual solver work.
+ HeuristicSolverImpl(const SimpleGraph &orig) :
+ solution(orig.getNumNodes(), true)
+ {
+ copyGraph(orig);
+ simplify();
+ setup();
+ computeSolution();
+ computeSolutionCost(orig);
+ }
+
+ /// \brief Returns the graph for this solver.
+ SolverGraph& getGraph() { return g; }
+
+ /// \brief Return the solution found by this solver.
+ const Solution& getSolution() const { return solution; }
+
+private:
+
+ /// \brief Add the given node to the appropriate bucket for its link
+ /// degree.
+ void addToBucket(const GraphNodeIterator &nodeItr) {
+ NodeData &nodeData = g.getNodeData(nodeItr);
+
+ switch (nodeData.getLinkDegree()) {
+ case 0: nodeData.setBucketItr(
+ r0Bucket.insert(r0Bucket.end(), nodeItr));
+ break;
+ case 1: nodeData.setBucketItr(
+ r1Bucket.insert(r1Bucket.end(), nodeItr));
+ break;
+ case 2: nodeData.setBucketItr(
+ r2Bucket.insert(r2Bucket.end(), nodeItr));
+ break;
+ default: heuristic.addToRNBucket(nodeItr);
+ break;
+ }
+ }
+
+ /// \brief Remove the given node from the appropriate bucket for its link
+ /// degree.
+ void removeFromBucket(const GraphNodeIterator &nodeItr) {
+ NodeData &nodeData = g.getNodeData(nodeItr);
+
+ switch (nodeData.getLinkDegree()) {
+ case 0: r0Bucket.erase(nodeData.getBucketItr()); break;
+ case 1: r1Bucket.erase(nodeData.getBucketItr()); break;
+ case 2: r2Bucket.erase(nodeData.getBucketItr()); break;
+ default: heuristic.removeFromRNBucket(nodeItr); break;
+ }
+ }
+
+public:
+
+ /// \brief Add a link.
+ void addLink(const GraphEdgeIterator &edgeItr) {
+ g.getEdgeData(edgeItr).setup(edgeItr);
+
+ if ((g.getNodeData(g.getEdgeNode1Itr(edgeItr)).getLinkDegree() > 2) ||
+ (g.getNodeData(g.getEdgeNode2Itr(edgeItr)).getLinkDegree() > 2)) {
+ heuristic.handleAddLink(edgeItr);
+ }
+ }
+
+ /// \brief Remove link, update info for node.
+ ///
+ /// Only updates information for the given node, since usually the other
+ /// is about to be removed.
+ void removeLink(const GraphEdgeIterator &edgeItr,
+ const GraphNodeIterator &nodeItr) {
+
+ if (g.getNodeData(nodeItr).getLinkDegree() > 2) {
+ heuristic.handleRemoveLink(edgeItr, nodeItr);
+ }
+ g.getEdgeData(edgeItr).unlink();
+ }
+
+ /// \brief Remove link, update info for both nodes. Useful for R2 only.
+ void removeLinkR2(const GraphEdgeIterator &edgeItr) {
+ GraphNodeIterator node1Itr = g.getEdgeNode1Itr(edgeItr);
+
+ if (g.getNodeData(node1Itr).getLinkDegree() > 2) {
+ heuristic.handleRemoveLink(edgeItr, node1Itr);
+ }
+ removeLink(edgeItr, g.getEdgeNode2Itr(edgeItr));
+ }
+
+ /// \brief Removes all links connected to the given node.
+ void unlinkNode(const GraphNodeIterator &nodeItr) {
+ NodeData &nodeData = g.getNodeData(nodeItr);
+
+ typedef std::vector<GraphEdgeIterator> TempEdgeList;
+
+ TempEdgeList edgesToUnlink;
+ edgesToUnlink.reserve(nodeData.getLinkDegree());
+
+ // Copy adj edges into a temp vector. We want to destroy them during
+ // the unlink, and we can't do that while we're iterating over them.
+ std::copy(nodeData.adjLinksBegin(), nodeData.adjLinksEnd(),
+ std::back_inserter(edgesToUnlink));
+
+ for (typename TempEdgeList::iterator
+ edgeItr = edgesToUnlink.begin(), edgeEnd = edgesToUnlink.end();
+ edgeItr != edgeEnd; ++edgeItr) {
+
+ GraphNodeIterator otherNode = g.getEdgeOtherNode(*edgeItr, nodeItr);
+
+ removeFromBucket(otherNode);
+ removeLink(*edgeItr, otherNode);
+ addToBucket(otherNode);
+ }
+ }
+
+ /// \brief Push the given node onto the stack to be solved with
+ /// backpropagation.
+ void pushStack(const GraphNodeIterator &nodeItr) {
+ stack.push_back(nodeItr);
+ }
+
+ /// \brief Set the solution of the given node.
+ void setSolution(const GraphNodeIterator &nodeItr, unsigned solIndex) {
+ solution.setSelection(g.getNodeID(nodeItr), solIndex);
+
+ for (GraphAdjEdgeIterator adjEdgeItr = g.adjEdgesBegin(nodeItr),
+ adjEdgeEnd = g.adjEdgesEnd(nodeItr);
+ adjEdgeItr != adjEdgeEnd; ++adjEdgeItr) {
+ GraphEdgeIterator edgeItr(*adjEdgeItr);
+ GraphNodeIterator adjNodeItr(g.getEdgeOtherNode(edgeItr, nodeItr));
+ g.getNodeData(adjNodeItr).addSolvedLink(edgeItr);
+ }
+ }
+
+private:
+
+ SolverGraph g;
+ Heuristic heuristic;
+ Solution solution;
+
+ NodeList r0Bucket,
+ r1Bucket,
+ r2Bucket;
+
+ NodeStack stack;
+
+ // Copy the SimpleGraph into an annotated graph which we can use for reduction.
+ void copyGraph(const SimpleGraph &orig) {
+
+ assert((g.getNumEdges() == 0) && (g.getNumNodes() == 0) &&
+ "Graph should be empty prior to solver setup.");
+
+ assert(orig.areNodeIDsValid() &&
+ "Cannot copy from a graph with invalid node IDs.");
+
+ std::vector<GraphNodeIterator> newNodeItrs;
+
+ for (unsigned nodeID = 0; nodeID < orig.getNumNodes(); ++nodeID) {
+ newNodeItrs.push_back(
+ g.addNode(orig.getNodeCosts(orig.getNodeItr(nodeID)), NodeData()));
+ }
+
+ for (SimpleGraph::ConstEdgeIterator
+ origEdgeItr = orig.edgesBegin(), origEdgeEnd = orig.edgesEnd();
+ origEdgeItr != origEdgeEnd; ++origEdgeItr) {
+
+ unsigned id1 = orig.getNodeID(orig.getEdgeNode1Itr(origEdgeItr)),
+ id2 = orig.getNodeID(orig.getEdgeNode2Itr(origEdgeItr));
+
+ g.addEdge(newNodeItrs[id1], newNodeItrs[id2],
+ orig.getEdgeCosts(origEdgeItr), EdgeData(g));
+ }
+
+ // Assign IDs to the new nodes using the ordering from the old graph,
+ // this will lead to nodes in the new graph getting the same ID as the
+ // corresponding node in the old graph.
+ g.assignNodeIDs(newNodeItrs);
+ }
+
+ // Simplify the annotated graph by eliminating independent edges and trivial
+ // nodes.
+ void simplify() {
+ disconnectTrivialNodes();
+ eliminateIndependentEdges();
+ }
+
+ // Eliminate trivial nodes.
+ void disconnectTrivialNodes() {
+ for (GraphNodeIterator nodeItr = g.nodesBegin(), nodeEnd = g.nodesEnd();
+ nodeItr != nodeEnd; ++nodeItr) {
+
+ if (g.getNodeCosts(nodeItr).getLength() == 1) {
+
+ std::vector<GraphEdgeIterator> edgesToRemove;
+
+ for (GraphAdjEdgeIterator adjEdgeItr = g.adjEdgesBegin(nodeItr),
+ adjEdgeEnd = g.adjEdgesEnd(nodeItr);
+ adjEdgeItr != adjEdgeEnd; ++adjEdgeItr) {
+
+ GraphEdgeIterator edgeItr = *adjEdgeItr;
+
+ if (g.getEdgeNode1Itr(edgeItr) == nodeItr) {
+ GraphNodeIterator otherNodeItr = g.getEdgeNode2Itr(edgeItr);
+ g.getNodeCosts(otherNodeItr) +=
+ g.getEdgeCosts(edgeItr).getRowAsVector(0);
+ }
+ else {
+ GraphNodeIterator otherNodeItr = g.getEdgeNode1Itr(edgeItr);
+ g.getNodeCosts(otherNodeItr) +=
+ g.getEdgeCosts(edgeItr).getColAsVector(0);
+ }
+
+ edgesToRemove.push_back(edgeItr);
+ }
+
+ while (!edgesToRemove.empty()) {
+ g.removeEdge(edgesToRemove.back());
+ edgesToRemove.pop_back();
+ }
+ }
+ }
+ }
+
+ void eliminateIndependentEdges() {
+ std::vector<GraphEdgeIterator> edgesToProcess;
+
+ for (GraphEdgeIterator edgeItr = g.edgesBegin(), edgeEnd = g.edgesEnd();
+ edgeItr != edgeEnd; ++edgeItr) {
+ edgesToProcess.push_back(edgeItr);
+ }
+
+ while (!edgesToProcess.empty()) {
+ tryToEliminateEdge(edgesToProcess.back());
+ edgesToProcess.pop_back();
+ }
+ }
+
+ void tryToEliminateEdge(const GraphEdgeIterator &edgeItr) {
+ if (tryNormaliseEdgeMatrix(edgeItr)) {
+ g.removeEdge(edgeItr);
+ }
+ }
+
+ bool tryNormaliseEdgeMatrix(const GraphEdgeIterator &edgeItr) {
+
+ Matrix &edgeCosts = g.getEdgeCosts(edgeItr);
+ Vector &uCosts = g.getNodeCosts(g.getEdgeNode1Itr(edgeItr)),
+ &vCosts = g.getNodeCosts(g.getEdgeNode2Itr(edgeItr));
+
+ for (unsigned r = 0; r < edgeCosts.getRows(); ++r) {
+ PBQPNum rowMin = edgeCosts.getRowMin(r);
+ uCosts[r] += rowMin;
+ if (rowMin != std::numeric_limits<PBQPNum>::infinity()) {
+ edgeCosts.subFromRow(r, rowMin);
+ }
+ else {
+ edgeCosts.setRow(r, 0);
+ }
+ }
+
+ for (unsigned c = 0; c < edgeCosts.getCols(); ++c) {
+ PBQPNum colMin = edgeCosts.getColMin(c);
+ vCosts[c] += colMin;
+ if (colMin != std::numeric_limits<PBQPNum>::infinity()) {
+ edgeCosts.subFromCol(c, colMin);
+ }
+ else {
+ edgeCosts.setCol(c, 0);
+ }
+ }
+
+ return edgeCosts.isZero();
+ }
+
+ void setup() {
+ setupLinks();
+ heuristic.initialise(*this);
+ setupBuckets();
+ }
+
+ void setupLinks() {
+ for (GraphEdgeIterator edgeItr = g.edgesBegin(), edgeEnd = g.edgesEnd();
+ edgeItr != edgeEnd; ++edgeItr) {
+ g.getEdgeData(edgeItr).setup(edgeItr);
+ }
+ }
+
+ void setupBuckets() {
+ for (GraphNodeIterator nodeItr = g.nodesBegin(), nodeEnd = g.nodesEnd();
+ nodeItr != nodeEnd; ++nodeItr) {
+ addToBucket(nodeItr);
+ }
+ }
+
+ void computeSolution() {
+ assert(g.areNodeIDsValid() &&
+ "Nodes cannot be added/removed during reduction.");
+
+ reduce();
+ computeTrivialSolutions();
+ backpropagate();
+ }
+
+ void printNode(const GraphNodeIterator &nodeItr) {
+ llvm::errs() << "Node " << g.getNodeID(nodeItr) << " (" << &*nodeItr << "):\n"
+ << " costs = " << g.getNodeCosts(nodeItr) << "\n"
+ << " link degree = " << g.getNodeData(nodeItr).getLinkDegree() << "\n"
+ << " links = [ ";
+
+ for (typename HSIT::NodeData::AdjLinkIterator
+ aeItr = g.getNodeData(nodeItr).adjLinksBegin(),
+ aeEnd = g.getNodeData(nodeItr).adjLinksEnd();
+ aeItr != aeEnd; ++aeItr) {
+ llvm::errs() << "(" << g.getNodeID(g.getEdgeNode1Itr(*aeItr))
+ << ", " << g.getNodeID(g.getEdgeNode2Itr(*aeItr))
+ << ") ";
+ }
+ llvm::errs() << "]\n";
+ }
+
+ void dumpState() {
+ llvm::errs() << "\n";
+
+ for (GraphNodeIterator nodeItr = g.nodesBegin(), nodeEnd = g.nodesEnd();
+ nodeItr != nodeEnd; ++nodeItr) {
+ printNode(nodeItr);
+ }
+
+ NodeList* buckets[] = { &r0Bucket, &r1Bucket, &r2Bucket };
+
+ for (unsigned b = 0; b < 3; ++b) {
+ NodeList &bucket = *buckets[b];
+
+ llvm::errs() << "Bucket " << b << ": [ ";
+
+ for (NodeListIterator nItr = bucket.begin(), nEnd = bucket.end();
+ nItr != nEnd; ++nItr) {
+ llvm::errs() << g.getNodeID(*nItr) << " ";
+ }
+
+ llvm::errs() << "]\n";
+ }
+
+ llvm::errs() << "Stack: [ ";
+ for (NodeStackIterator nsItr = stack.begin(), nsEnd = stack.end();
+ nsItr != nsEnd; ++nsItr) {
+ llvm::errs() << g.getNodeID(*nsItr) << " ";
+ }
+ llvm::errs() << "]\n";
+ }
+
+ void reduce() {
+ bool reductionFinished = r1Bucket.empty() && r2Bucket.empty() &&
+ heuristic.rNBucketEmpty();
+
+ while (!reductionFinished) {
+
+ if (!r1Bucket.empty()) {
+ processR1();
+ }
+ else if (!r2Bucket.empty()) {
+ processR2();
+ }
+ else if (!heuristic.rNBucketEmpty()) {
+ solution.setProvedOptimal(false);
+ solution.incRNReductions();
+ heuristic.processRN();
+ }
+ else reductionFinished = true;
+ }
+
+ };
+
+ void processR1() {
+
+ // Remove the first node in the R0 bucket:
+ GraphNodeIterator xNodeItr = r1Bucket.front();
+ r1Bucket.pop_front();
+
+ solution.incR1Reductions();
+
+ //llvm::errs() << "Applying R1 to " << g.getNodeID(xNodeItr) << "\n";
+
+ assert((g.getNodeData(xNodeItr).getLinkDegree() == 1) &&
+ "Node in R1 bucket has degree != 1");
+
+ GraphEdgeIterator edgeItr = *g.getNodeData(xNodeItr).adjLinksBegin();
+
+ const Matrix &edgeCosts = g.getEdgeCosts(edgeItr);
+
+ const Vector &xCosts = g.getNodeCosts(xNodeItr);
+ unsigned xLen = xCosts.getLength();
+
+ // Duplicate a little code to avoid transposing matrices:
+ if (xNodeItr == g.getEdgeNode1Itr(edgeItr)) {
+ GraphNodeIterator yNodeItr = g.getEdgeNode2Itr(edgeItr);
+ Vector &yCosts = g.getNodeCosts(yNodeItr);
+ unsigned yLen = yCosts.getLength();
+
+ for (unsigned j = 0; j < yLen; ++j) {
+ PBQPNum min = edgeCosts[0][j] + xCosts[0];
+ for (unsigned i = 1; i < xLen; ++i) {
+ PBQPNum c = edgeCosts[i][j] + xCosts[i];
+ if (c < min)
+ min = c;
+ }
+ yCosts[j] += min;
+ }
+ }
+ else {
+ GraphNodeIterator yNodeItr = g.getEdgeNode1Itr(edgeItr);
+ Vector &yCosts = g.getNodeCosts(yNodeItr);
+ unsigned yLen = yCosts.getLength();
+
+ for (unsigned i = 0; i < yLen; ++i) {
+ PBQPNum min = edgeCosts[i][0] + xCosts[0];
+
+ for (unsigned j = 1; j < xLen; ++j) {
+ PBQPNum c = edgeCosts[i][j] + xCosts[j];
+ if (c < min)
+ min = c;
+ }
+ yCosts[i] += min;
+ }
+ }
+
+ unlinkNode(xNodeItr);
+ pushStack(xNodeItr);
+ }
+
+ void processR2() {
+
+ GraphNodeIterator xNodeItr = r2Bucket.front();
+ r2Bucket.pop_front();
+
+ solution.incR2Reductions();
+
+ // Unlink is unsafe here. At some point it may optimistically more a node
+ // to a lower-degree list when its degree will later rise, or vice versa,
+ // violating the assumption that node degrees monotonically decrease
+ // during the reduction phase. Instead we'll bucket shuffle manually.
+ pushStack(xNodeItr);
+
+ assert((g.getNodeData(xNodeItr).getLinkDegree() == 2) &&
+ "Node in R2 bucket has degree != 2");
+
+ const Vector &xCosts = g.getNodeCosts(xNodeItr);
+
+ typename NodeData::AdjLinkIterator tempItr =
+ g.getNodeData(xNodeItr).adjLinksBegin();
+
+ GraphEdgeIterator yxEdgeItr = *tempItr,
+ zxEdgeItr = *(++tempItr);
+
+ GraphNodeIterator yNodeItr = g.getEdgeOtherNode(yxEdgeItr, xNodeItr),
+ zNodeItr = g.getEdgeOtherNode(zxEdgeItr, xNodeItr);
+
+ removeFromBucket(yNodeItr);
+ removeFromBucket(zNodeItr);
+
+ removeLink(yxEdgeItr, yNodeItr);
+ removeLink(zxEdgeItr, zNodeItr);
+
+ // Graph some of the costs:
+ bool flipEdge1 = (g.getEdgeNode1Itr(yxEdgeItr) == xNodeItr),
+ flipEdge2 = (g.getEdgeNode1Itr(zxEdgeItr) == xNodeItr);
+
+ const Matrix *yxCosts = flipEdge1 ?
+ new Matrix(g.getEdgeCosts(yxEdgeItr).transpose()) :
+ &g.getEdgeCosts(yxEdgeItr),
+ *zxCosts = flipEdge2 ?
+ new Matrix(g.getEdgeCosts(zxEdgeItr).transpose()) :
+ &g.getEdgeCosts(zxEdgeItr);
+
+ unsigned xLen = xCosts.getLength(),
+ yLen = yxCosts->getRows(),
+ zLen = zxCosts->getRows();
+
+ // Compute delta:
+ Matrix delta(yLen, zLen);
+
+ for (unsigned i = 0; i < yLen; ++i) {
+ for (unsigned j = 0; j < zLen; ++j) {
+ PBQPNum min = (*yxCosts)[i][0] + (*zxCosts)[j][0] + xCosts[0];
+ for (unsigned k = 1; k < xLen; ++k) {
+ PBQPNum c = (*yxCosts)[i][k] + (*zxCosts)[j][k] + xCosts[k];
+ if (c < min) {
+ min = c;
+ }
+ }
+ delta[i][j] = min;
+ }
+ }
+
+ if (flipEdge1)
+ delete yxCosts;
+
+ if (flipEdge2)
+ delete zxCosts;
+
+ // Deal with the potentially induced yz edge.
+ GraphEdgeIterator yzEdgeItr = g.findEdge(yNodeItr, zNodeItr);
+ if (yzEdgeItr == g.edgesEnd()) {
+ yzEdgeItr = g.addEdge(yNodeItr, zNodeItr, delta, EdgeData(g));
+ }
+ else {
+ // There was an edge, but we're going to screw with it. Delete the old
+ // link, update the costs. We'll re-link it later.
+ removeLinkR2(yzEdgeItr);
+ g.getEdgeCosts(yzEdgeItr) +=
+ (yNodeItr == g.getEdgeNode1Itr(yzEdgeItr)) ?
+ delta : delta.transpose();
+ }
+
+ bool nullCostEdge = tryNormaliseEdgeMatrix(yzEdgeItr);
+
+ // Nulled the edge, remove it entirely.
+ if (nullCostEdge) {
+ g.removeEdge(yzEdgeItr);
+ }
+ else {
+ // Edge remains - re-link it.
+ addLink(yzEdgeItr);
+ }
+
+ addToBucket(yNodeItr);
+ addToBucket(zNodeItr);
+ }
+
+ void computeTrivialSolutions() {
+
+ for (NodeListIterator r0Itr = r0Bucket.begin(), r0End = r0Bucket.end();
+ r0Itr != r0End; ++r0Itr) {
+ GraphNodeIterator nodeItr = *r0Itr;
+
+ solution.incR0Reductions();
+ setSolution(nodeItr, g.getNodeCosts(nodeItr).minIndex());
+ }
+
+ }
+
+ void backpropagate() {
+ while (!stack.empty()) {
+ computeSolution(stack.back());
+ stack.pop_back();
+ }
+ }
+
+ void computeSolution(const GraphNodeIterator &nodeItr) {
+
+ NodeData &nodeData = g.getNodeData(nodeItr);
+
+ Vector v(g.getNodeCosts(nodeItr));
+
+ // Solve based on existing links.
+ for (typename NodeData::AdjLinkIterator
+ solvedLinkItr = nodeData.solvedLinksBegin(),
+ solvedLinkEnd = nodeData.solvedLinksEnd();
+ solvedLinkItr != solvedLinkEnd; ++solvedLinkItr) {
+
+ GraphEdgeIterator solvedEdgeItr(*solvedLinkItr);
+ Matrix &edgeCosts = g.getEdgeCosts(solvedEdgeItr);
+
+ if (nodeItr == g.getEdgeNode1Itr(solvedEdgeItr)) {
+ GraphNodeIterator adjNode(g.getEdgeNode2Itr(solvedEdgeItr));
+ unsigned adjSolution =
+ solution.getSelection(g.getNodeID(adjNode));
+ v += edgeCosts.getColAsVector(adjSolution);
+ }
+ else {
+ GraphNodeIterator adjNode(g.getEdgeNode1Itr(solvedEdgeItr));
+ unsigned adjSolution =
+ solution.getSelection(g.getNodeID(adjNode));
+ v += edgeCosts.getRowAsVector(adjSolution);
+ }
+
+ }
+
+ setSolution(nodeItr, v.minIndex());
+ }
+
+ void computeSolutionCost(const SimpleGraph &orig) {
+ PBQPNum cost = 0.0;
+
+ for (SimpleGraph::ConstNodeIterator
+ nodeItr = orig.nodesBegin(), nodeEnd = orig.nodesEnd();
+ nodeItr != nodeEnd; ++nodeItr) {
+
+ unsigned nodeId = orig.getNodeID(nodeItr);
+
+ cost += orig.getNodeCosts(nodeItr)[solution.getSelection(nodeId)];
+ }
+
+ for (SimpleGraph::ConstEdgeIterator
+ edgeItr = orig.edgesBegin(), edgeEnd = orig.edgesEnd();
+ edgeItr != edgeEnd; ++edgeItr) {
+
+ SimpleGraph::ConstNodeIterator n1 = orig.getEdgeNode1Itr(edgeItr),
+ n2 = orig.getEdgeNode2Itr(edgeItr);
+ unsigned sol1 = solution.getSelection(orig.getNodeID(n1)),
+ sol2 = solution.getSelection(orig.getNodeID(n2));
+
+ cost += orig.getEdgeCosts(edgeItr)[sol1][sol2];
+ }
+
+ solution.setSolutionCost(cost);
+ }
+
+};
+
+template <typename Heuristic>
+class HeuristicSolver : public Solver {
+public:
+ Solution solve(const SimpleGraph &g) const {
+ HeuristicSolverImpl<Heuristic> solverImpl(g);
+ return solverImpl.getSolution();
+ }
+};
+
+}
+
+#endif // LLVM_CODEGEN_PBQP_HEURISTICSOLVER_H
generated by cgit v1.2.3 (git 2.25.1) at 2025-08-02 04:24:04 +0000