[verifier] [bug] Fix a bug when removing common prefix gates and do not generate hashing distribution in test_optimization_steps.h (#208)

Author: xumingkuan

src/benchmark/benchmark_optimization_steps.cpp

@@ -40,6 +40,8 @@ int main() {
   auto xfers = GraphXfer::get_all_xfers_from_ecc(
       &ctx,
       (kQuartzRootPath / "eccset/Nam_6_3_complete_ECC_set.json").string());
+  int verified_count = 0;
+  int not_verified_count = 0;
   for (const auto &circuit : kCircuitNames) {
     freopen(((kQuartzRootPath / "benchmark-logs" / circuit).string() + ".log")
                 .c_str(),
@@ -57,9 +59,14 @@ int main() {
         /*verbose=*/false);
     if (verified) {
       std::cout << "All transformations are verified." << std::endl;
+      verified_count++;
     } else {
       std::cout << "Some transformation is not verified." << std::endl;
+      not_verified_count++;
+      std::cerr << circuit << " not verified." << std::endl;
     }
   }
+  std::cerr << verified_count << " cases verified, " << not_verified_count
+            << " cases not verified." << std::endl;
   return 0;
 }

src/quartz/dataset/dataset.cpp

@@ -175,6 +175,13 @@ bool Dataset::insert(Context *ctx, std::unique_ptr<CircuitSeq> dag) {
   return ret;
 }
 
+bool Dataset::insert_with_hash(const CircuitSeqHashType &hash_value,
+                               std::unique_ptr<CircuitSeq> dag) {
+  bool ret = dataset.count(hash_value) == 0;
+  dataset[hash_value].push_back(std::move(dag));
+  return ret;
+}
+
 bool Dataset::insert_to_nearby_set_if_exists(Context *ctx,
                                              std::unique_ptr<CircuitSeq> dag) {
   const auto hash_value = dag->hash(ctx);

src/quartz/dataset/dataset.h

@@ -40,7 +40,18 @@ class Dataset {
   // Returns true iff the hash value is new to the |dataset|.
   bool insert(Context *ctx, std::unique_ptr<CircuitSeq> dag);
 
-  // Inserts the circuitseq to an existing set if the hash value plus or minus 1
+  /**
+   * Insert a CircuitSeq with a pre-defined hash value. This function is used
+   * when the hash value cannot be computed, and should NOT be used in Quartz's
+   * generator.
+   * @param hash_value The hash value to be inserted.
+   * @param dag The CircuitSeq to be inserted.
+   * @return True iff the hash value is new to the |dataset|.
+   */
+  bool insert_with_hash(const CircuitSeqHashType &hash_value,
+                        std::unique_ptr<CircuitSeq> dag);
+
+  // Inserts the CircuitSeq to an existing set if the hash value plus or minus 1
   // is found. Returns true iff there is no such existing set.
   bool insert_to_nearby_set_if_exists(Context *ctx,
                                       std::unique_ptr<CircuitSeq> dag);

src/quartz/verifier/verifier.cpp

@@ -67,7 +67,7 @@ bool Verifier::equivalent(Context *ctx, const CircuitSeq *circuit1,
   std::unordered_set<CircuitGate *> leftover_gates_start2;
   // (Partial) topological sort on circuit1
   while (!wires_to_search.empty()) {
-    auto wire1 = wires_to_search.front();
+    CircuitWire *wire1 = wires_to_search.front();
     assert(wires_mapping.count(wire1) > 0);
     auto wire2 = wires_mapping[wire1];
     wires_to_search.pop();
@@ -79,19 +79,31 @@ bool Verifier::equivalent(Context *ctx, const CircuitSeq *circuit1,
                     [&qubit_blocked](CircuitWire *output_wire) {
                       return qubit_blocked[output_wire->index];
                     })) {
-      // Block qubits of potential unmatched gates
-      for (auto &gate : wire1->output_gates) {
-        for (auto &output_wire : gate->output_wires) {
-          qubit_blocked[output_wire->index] = true;
+      // Block qubits of potential unmatched gates.
+      for (auto &gate1 : wire1->output_gates) {
+        // Use a for loop because |wire1->output_gates| can be empty.
+        for (auto &input_wire : gate1->input_wires) {
+          qubit_blocked[input_wire->index] = true;
+          // If |wires_mapping| does not have |input_wire|, this means that
+          // the qubit is already blocked before, and |leftover_gates_start2|
+          // already had an earlier gate at this qubit.
+          if (wires_mapping.count(input_wire) > 0) {
+            // Note that this input wire might be not in the search queue now.
+            // We need to manually add the gate in circuit2 to the frontier.
+            for (auto &gate : wires_mapping[input_wire]->output_gates) {
+              leftover_gates_start2.insert(gate);
+            }
+          }
         }
         // Use std::unordered_set to deduplicate, similarly hereinafter
-        leftover_gates_start1.insert(gate);
+        leftover_gates_start1.insert(gate1);
       }
-      for (auto &gate : wire2->output_gates) {
-        for (auto &output_wire : gate->output_wires) {
+      for (auto &gate2 : wire2->output_gates) {
+        // Use a for loop because |wire2->output_gates| can be empty.
+        for (auto &output_wire : gate2->output_wires) {
           qubit_blocked[output_wire->index] = true;
         }
-        leftover_gates_start2.insert(gate);
+        leftover_gates_start2.insert(gate2);
       }
       continue;
     }
@@ -141,6 +153,20 @@ bool Verifier::equivalent(Context *ctx, const CircuitSeq *circuit1,
   // We should have removed the same number of gates
   assert(circuit1->get_num_gates() - c1->get_num_gates() ==
          circuit2->get_num_gates() - c2->get_num_gates());
+  if (verbose) {
+    std::cout << "Removed " << circuit1->get_num_gates() - c1->get_num_gates()
+              << " prefix gates from circuit1 and "
+              << circuit2->get_num_gates() - c2->get_num_gates()
+              << " prefix gates from circuit2." << std::endl;
+    std::cout << "Leftover gates from circuit1:" << std::endl;
+    for (auto &gate : leftover_gates_start1) {
+      std::cout << gate->to_string() << std::endl;
+    }
+    std::cout << "Leftover gates from circuit2:" << std::endl;
+    for (auto &gate : leftover_gates_start2) {
+      std::cout << gate->to_string() << std::endl;
+    }
+  }
 
   // Remove common last gates
   while (true) {

src/test/test_optimization_steps.h

@@ -21,9 +21,11 @@ void test_optimization(
     std::cerr << "Parser failed" << std::endl;
     return;
   }
-  ctx->gen_input_and_hashing_dis(dag->get_num_qubits());
+  // Do not generate (this is only for CircuitSeq::hash())
+  // because the number of qubits can be large.
+  // ctx->gen_input_and_hashing_dis(dag->get_num_qubits());
 
-  quartz::Graph graph(ctx, dag);
+  Graph graph(ctx, dag);
   std::cout << graph.total_cost() << " gates in circuit before optimizing."
             << std::endl;
   auto start = std::chrono::steady_clock::now();