Issue 92 Classical Ordering (#96)

pytket/phir/cli.py

@@ -59,7 +59,7 @@ def main() -> None:
     for file in args.qasm_files:
         print(f"Processing {file}")  # noqa: T201
         c = circuit_from_qasm(file)
-        tket_opt_level = int(args.tk)
+        tket_opt_level = int(args.tket_opt_level)
         rc = rebase_to_qtm_machine(c, args.machine, tket_opt_level)
         qasm = circuit_to_qasm_str(rc, header="hqslib1")
         circ = circuit_from_qasm_str(qasm)

pytket/phir/sharding/sharder.py

@@ -194,7 +194,7 @@ def _resolve_shard_dependencies(
                     "...adding shard dep %s -> WAW", self._bit_written_by[bit_written]
                 )
                 depends_upon.add(self._bit_written_by[bit_written])
-            elif bit_written in self._bit_read_by:
+            if bit_written in self._bit_read_by:
                 logger.debug(
                     "...adding shard dep %s -> WAR", self._bit_read_by[bit_written]
                 )

tests/data/qasm/classical_ordering.qasm

@@ -0,0 +1,11 @@
+OPENQASM 2.0;
+include "hqslib1.inc";
+
+qreg q[1];
+creg a[4];
+creg b[4];
+creg c[4];
+a = 3;
+b = a;
+c = (a - b);
+a = (a << 1);

tests/test_sharder.py

@@ -143,7 +143,7 @@ def test_simple_conditional(self) -> None:
         assert shards[3].qubits_used == {circuit.qubits[0]}
         assert shards[3].bits_written == {circuit.bits[0]}
         assert shards[3].bits_read == {circuit.bits[0]}
-        assert shards[3].depends_upon == {shards[0].ID, shards[1].ID}
+        assert shards[3].depends_upon == {shards[0].ID, shards[1].ID, shards[2].ID}
         assert len(shards[3].sub_commands.items()) == 1
         s2_qubit, s2_sub_cmds = next(iter(shards[3].sub_commands.items()))
         assert s2_qubit == circuit.qubits[0]
@@ -274,7 +274,7 @@ def test_classical_hazards(self) -> None:
         assert shards[3].qubits_used == set()
         assert shards[3].bits_written == {circuit.bits[0]}
         assert shards[3].bits_read == {circuit.bits[0]}
-        assert shards[3].depends_upon == {shards[0].ID}
+        assert shards[3].depends_upon == {shards[0].ID, shards[2].ID}
 
         # shard 4: [] if(c[2]==1) c[0]=1;
         assert shards[4].primary_command.op.type == OpType.Conditional
@@ -307,3 +307,94 @@ def test_with_big_gate(self) -> None:
         assert len(shards[1].sub_commands) == 0
         assert shards[1].qubits_used == {circuit.qubits[3]}
         assert shards[1].bits_written == {circuit.bits[0]}
+
+    def test_classical_ordering_breaking_circuit(self) -> None:
+        circuit = get_qasm_as_circuit(QasmFile.classical_ordering)
+        sharder = Sharder(circuit)
+        shards = sharder.shard()
+
+        assert len(shards) == 4
+
+        # shard 0
+        assert shards[0].primary_command.op.type == OpType.SetBits
+        assert len(shards[0].sub_commands.items()) == 0
+        assert shards[0].qubits_used == set()
+        assert shards[0].bits_written == {
+            circuit.bits[0],
+            circuit.bits[1],
+            circuit.bits[2],
+            circuit.bits[3],
+        }
+        assert shards[0].bits_read == {
+            circuit.bits[0],
+            circuit.bits[1],
+            circuit.bits[2],
+            circuit.bits[3],
+        }
+        assert shards[0].depends_upon == set()
+
+        # shard 1
+        assert shards[1].primary_command.op.type == OpType.CopyBits
+        assert len(shards[1].sub_commands.items()) == 0
+        assert shards[1].qubits_used == set()
+        assert shards[1].bits_written == {
+            circuit.bits[4],
+            circuit.bits[5],
+            circuit.bits[6],
+            circuit.bits[7],
+        }
+        assert shards[1].bits_read == {
+            circuit.bits[0],
+            circuit.bits[1],
+            circuit.bits[2],
+            circuit.bits[3],
+            circuit.bits[4],
+            circuit.bits[5],
+            circuit.bits[6],
+            circuit.bits[7],
+        }
+        assert shards[1].depends_upon == {shards[0].ID}
+
+        # shard 2
+        assert shards[2].primary_command.op.type == OpType.ClassicalExpBox
+        assert len(shards[2].sub_commands.items()) == 0
+        assert shards[2].qubits_used == set()
+        assert shards[2].bits_written == {
+            circuit.bits[8],
+            circuit.bits[9],
+            circuit.bits[10],
+            circuit.bits[11],
+        }
+        assert shards[2].bits_read == {
+            circuit.bits[0],
+            circuit.bits[1],
+            circuit.bits[2],
+            circuit.bits[3],
+            circuit.bits[4],
+            circuit.bits[5],
+            circuit.bits[6],
+            circuit.bits[7],
+            circuit.bits[8],
+            circuit.bits[9],
+            circuit.bits[10],
+            circuit.bits[11],
+        }
+        assert shards[2].depends_upon == {shards[0].ID, shards[1].ID}
+
+        # shard 2
+        assert shards[3].primary_command.op.type == OpType.ClassicalExpBox
+        assert len(shards[3].sub_commands.items()) == 0
+        assert shards[3].qubits_used == set()
+        assert shards[3].bits_written == {
+            circuit.bits[0],
+            circuit.bits[1],
+            circuit.bits[2],
+            circuit.bits[3],
+        }
+        assert shards[3].bits_read == {
+            circuit.bits[0],
+            circuit.bits[1],
+            circuit.bits[2],
+            circuit.bits[3],
+        }
+        assert shards[3].depends_upon == {shards[0].ID, shards[2].ID}

tests/test_utils.py

@@ -42,6 +42,7 @@ class QasmFile(Enum):
     tk2_same_angle = auto()
     tk2_diff_angles = auto()
     rxrz = auto()
+    classical_ordering = auto()
 
 
 def get_qasm_as_circuit(qasm_file: QasmFile) -> "Circuit":