Merge pull request #2245 from OlivierHamel/fix-profiler-cost-est

Fix profiler cost estimate

src/ast/utility/SipsMetric.cpp

@@ -53,6 +53,7 @@ std::vector<std::size_t> StaticSipsMetric::getReordering(
     while (numAdded < atoms.size()) {
         // grab the index of the next atom, based on the SIPS function
         const auto& costs = evaluateCosts(atoms, bindingStore);
+        assert(atoms.size() == costs.size() && "each atom should have exactly one cost");
         std::size_t minIdx = static_cast<std::size_t>(
                 std::distance(costs.begin(), std::min_element(costs.begin(), costs.end())));
         const auto* nextAtom = atoms[minIdx];
@@ -700,7 +701,7 @@ std::vector<double> ProfileUseSips::evaluateCosts(
         // prioritise propositions
         std::size_t arity = atom->getArity();
         if (arity == 0) {
-            cost.push_back(0);
+            cost.push_back(-1);  // cheaper than any non-proposition
             continue;
         }
 
@@ -709,6 +710,7 @@ std::vector<double> ProfileUseSips::evaluateCosts(
         std::size_t numFree = arity - numBound;
         double value = log(profileUse.getRelationSize(atom->getQualifiedName()));
         value *= (numFree * 1.0) / arity;
+        cost.push_back(value);
     }
     return cost;
 }