New C++ PBQP solver. Currently about as fast (read _slow_) as the old C based solver, but I'll be working to improve that. The PBQP allocator has been updated to use the new solver.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78354 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/PBQP/ExhaustiveSolver.h

@@ -0,0 +1,93 @@
+#ifndef LLVM_CODEGEN_PBQP_EXHAUSTIVESOLVER_H
+#define LLVM_CODEGEN_PBQP_EXHAUSTIVESOLVER_H
+
+#include "Solver.h"
+
+namespace PBQP {
+
+class ExhaustiveSolverImpl {
+private:
+
+  const SimpleGraph &g;
+
+  PBQPNum getSolutionCost(const Solution &solution) const {
+    PBQPNum cost = 0.0;
+    
+    for (SimpleGraph::ConstNodeIterator
+         nodeItr = g.nodesBegin(), nodeEnd = g.nodesEnd();
+         nodeItr != nodeEnd; ++nodeItr) {
+      
+      unsigned nodeId = g.getNodeID(nodeItr);
+
+      cost += g.getNodeCosts(nodeItr)[solution.getSelection(nodeId)];
+    }
+
+    for (SimpleGraph::ConstEdgeIterator
+         edgeItr = g.edgesBegin(), edgeEnd = g.edgesEnd();
+         edgeItr != edgeEnd; ++edgeItr) {
+      
+      SimpleGraph::ConstNodeIterator n1 = g.getEdgeNode1Itr(edgeItr),
+                                     n2 = g.getEdgeNode2Itr(edgeItr);
+      unsigned sol1 = solution.getSelection(g.getNodeID(n1)),
+               sol2 = solution.getSelection(g.getNodeID(n2));
+
+      cost += g.getEdgeCosts(edgeItr)[sol1][sol2];
+    }
+
+    return cost;
+  }
+
+public:
+
+  ExhaustiveSolverImpl(const SimpleGraph &g) : g(g) {}
+
+  Solution solve() const {
+    Solution current(g.getNumNodes(), true), optimal(current);
+
+    PBQPNum bestCost = std::numeric_limits<PBQPNum>::infinity();
+    bool finished = false;
+
+    while (!finished) {
+      PBQPNum currentCost = getSolutionCost(current);
+
+      if (currentCost < bestCost) {
+        optimal = current;
+        bestCost = currentCost;
+      }
+
+      // assume we're done.
+      finished = true;
+
+      for (unsigned i = 0; i < g.getNumNodes(); ++i) {
+        if (current.getSelection(i) ==
+            (g.getNodeCosts(g.getNodeItr(i)).getLength() - 1)) {
+          current.setSelection(i, 0);
+        }
+        else {
+          current.setSelection(i, current.getSelection(i) + 1);
+          finished = false;
+          break;
+        }
+      }
+
+    }
+
+    optimal.setSolutionCost(bestCost);
+
+    return optimal;
+  }
+
+};
+
+class ExhaustiveSolver : public Solver {
+public:
+  ~ExhaustiveSolver() {}
+  Solution solve(const SimpleGraph &g) const {
+    ExhaustiveSolverImpl solver(g);
+    return solver.solve();
+  }
+};
+
+}
+
+#endif // LLVM_CODGEN_PBQP_EXHAUSTIVESOLVER_HPP