Assert candidate swaps size (#108)

* Add assertion that there are at least some swaps to trial * Pseudo code for Yao * Fix routing with measurements issue * Add classically controlled gates to lexiroute test Co-authored-by: sjdilkes <[email protected]>
CQCL · Nov 9, 2021 · 4c92d8d · 4c92d8d
1 parent 5b50029
commit 4c92d8d
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Showing 3 changed files with 57 additions and 5 deletions.
diff --git a/tket/src/Mapping/LexiRoute.cpp b/tket/src/Mapping/LexiRoute.cpp
@@ -464,6 +464,8 @@ void LexiRoute::solve(unsigned lookahead) {
   }
   swap_set_t candidate_swaps = this->get_candidate_swaps();
   this->remove_swaps_decreasing(candidate_swaps);
+
+  TKET_ASSERT(candidate_swaps.size() != 0);
   // Only want to substitute a single swap
   // check next layer of interacting qubits and remove swaps until only one
   // lexicographically superior swap is left
@@ -488,17 +490,18 @@ void LexiRoute::solve(unsigned lookahead) {
     // architecture
     this->set_interacting_uids(true);
   }
-
+  // find best swap
   auto it = candidate_swaps.end();
   --it;
+
   std::pair<Node, Node> chosen_swap = *it;
   this->mapping_frontier_->set_quantum_boundary(copy);
 
   this->set_interacting_uids();
   std::pair<bool, bool> check = this->check_bridge(chosen_swap, lookahead);
-
   // set for final time, to allow gates to be correctly inserted, but then leave
   // as is
+  // insert gates
   this->mapping_frontier_->set_quantum_boundary(copy);
   if (!check.first && !check.second) {
     // update circuit with new swap
@@ -522,8 +525,10 @@ void LexiRoute::solve(unsigned lookahead) {
       this->mapping_frontier_->add_bridge(chosen_swap.second, central, target);
     }
   }
+
   // TODO: Refactor the following to happen during add_swap and add_bridge
   // methods
+  // add ancilla qubits if necessary
   if (copy.size() < this->mapping_frontier_->quantum_boundary->size()) {
     // implies ancilla qubit is added
     // find ancilla qubit, find swap vertex and port by looking at boundary,
@@ -557,6 +562,7 @@ void LexiRoute::solve(unsigned lookahead) {
       }
     }
   }
+
   return;
 }
 

diff --git a/tket/src/Mapping/MappingFrontier.cpp b/tket/src/Mapping/MappingFrontier.cpp
@@ -162,10 +162,23 @@ void MappingFrontier::advance_frontier_boundary(
     // TODO: add optional skip function later to skip vertices that don't have
     // physical requirements
     boundary_updated = false;
-    CutFrontier next_cut = this->circuit_.next_cut(
+
+    std::shared_ptr<unit_frontier_t> frontier_edges =
         frontier_convert_vertport_to_edge(
-            this->circuit_, this->quantum_boundary),
-        std::make_shared<b_frontier_t>());
+            this->circuit_, this->quantum_boundary);
+    // Add all classical edges that share the same target
+    unsigned dummy_bit_index = 0;
+    for (const std::pair<UnitID, Edge>& pair : frontier_edges->get<TagKey>()) {
+      Vertex vert = this->circuit_.target(pair.second);
+      for (const Edge& e :
+           this->circuit_.get_in_edges_of_type(vert, EdgeType::Classical)) {
+        frontier_edges->insert({Bit(dummy_bit_index), e});
+        dummy_bit_index++;
+      }
+    }
+
+    CutFrontier next_cut = this->circuit_.next_cut(
+        frontier_edges, std::make_shared<b_frontier_t>());
 
     // For each vertex in a slice, if its physically permitted, update
     // quantum_boundary with quantum out edges from vertex (i.e.

diff --git a/tket/tests/test_LexiRoute.cpp b/tket/tests/test_LexiRoute.cpp
@@ -242,6 +242,39 @@ SCENARIO("Test LexiRoute::solve") {
     LexiRoute lr1(shared_arc, mf);
     lr1.solve(20);
   }
+
+  GIVEN(
+      "Single best solution, with measurements and classically controlled "
+      "gates.") {
+    Circuit circ(6, 1);
+    std::vector<Qubit> qubits = circ.all_qubits();
+    circ.add_conditional_gate<unsigned>(OpType::CX, {}, {0, 2}, {0}, 1);
+    circ.add_op<UnitID>(OpType::CX, {qubits[1], qubits[3]});
+    circ.add_conditional_gate<unsigned>(OpType::X, {}, {0}, {0}, 1);
+    circ.add_op<UnitID>(OpType::Measure, {qubits[1], Bit(0)});
+    circ.add_op<UnitID>(OpType::CX, {qubits[4], qubits[5]});
+    circ.add_op<UnitID>(OpType::Measure, {qubits[3], Bit(0)});
+    // n0 -- n1 -- n2 -- n3 -- n4
+    //             |     |
+    //             n5    n7
+    //             |
+    //             n6
+    std::map<UnitID, UnitID> rename_map = {
+        {qubits[0], nodes[0]}, {qubits[1], nodes[1]}, {qubits[2], nodes[2]},
+        {qubits[3], nodes[3]}, {qubits[4], nodes[6]}, {qubits[5], nodes[5]}};
+    circ.rename_units(rename_map);
+    std::shared_ptr<MappingFrontier> mf =
+        std::make_shared<MappingFrontier>(circ);
+    LexiRoute lr(shared_arc, mf);
+
+    lr.solve(4);
+    std::vector<Command> commands = mf->circuit_.get_commands();
+    REQUIRE(commands.size() == 7);
+    Command swap_c = commands[1];
+    unit_vector_t uids = {nodes[1], nodes[2]};
+    REQUIRE(swap_c.get_args() == uids);
+    REQUIRE(*swap_c.get_op_ptr() == *get_op_ptr(OpType::SWAP));
+  }
 }
 SCENARIO("Test LexiRouteRoutingMethod") {
   std::vector<Node> nodes = {