stricter ordering checks (#112)

Co-authored-by: Kartik Singhal <[email protected]>

pytket/phir/api.py

@@ -69,6 +69,7 @@ def pytket_to_phir(circuit: "Circuit", qtm_machine: QtmMachine | None = None) ->
     else:
         phir_json = genphir(placed, machine_ops=bool(machine))
     if logger.getEffectiveLevel() <= logging.INFO:
+        print("PHIR JSON:")
         print(PHIRModel.model_validate_json(phir_json))
     return phir_json
 

pytket/phir/cli.py

@@ -9,6 +9,7 @@
 # mypy: disable-error-code="misc"
 # ruff: noqa: T201
 
+import logging
 from argparse import ArgumentParser
 from importlib.metadata import version
 
@@ -70,10 +71,9 @@ def main() -> None:
             case "H1-2":
                 machine = QtmMachine.H1_2
 
-        phir = pytket_to_phir(circuit, machine)
         if args.verbose:
-            print("\nPHIR to be simulated:")
-            print(phir)
+            logging.basicConfig(level=logging.INFO)
+        phir = pytket_to_phir(circuit, machine)
 
         print("\nPECOS results:")
         print(

pytket/phir/phirgen_parallel.py

@@ -10,6 +10,7 @@
 
 import json
 import logging
+from collections import OrderedDict
 from typing import TYPE_CHECKING
 
 import pytket.circuit as tk
@@ -29,14 +30,33 @@
 logger = logging.getLogger(__name__)
 
 
+def exec_order_preserved_helper(
+    ordered_dict: OrderedDict["UnitID", int], group_number: int, qubit_last_group: int
+) -> bool:
+    """A helper to determine whether order is preserved when adding qubits to groups."""
+    # determine whether the current group number is later in execution
+    # than the last group in which a qubit was used
+    group_eligible = group_number > qubit_last_group
+    if not group_eligible:
+        return False
+    for group in ordered_dict.values():
+        if group == qubit_last_group:
+            order_preserved = False
+            break
+        if group == group_number:
+            order_preserved = True
+            break
+    return order_preserved
+
+
 def process_sub_commands(
     sub_commands: dict["UnitID", list[tk.Command]], max_parallel_sq_gates: int
 ) -> dict[int, list[tk.Command]]:
     """Create parallelizable groups of sub-commands."""
     groups: dict[
         int, list[tk.Command]
     ] = {}  # be sure to order by group number into a list when returning
-    qubits2groups = {}  # track the most recent group in which a qubit was used
+    qubits2groups = OrderedDict()  # the most recent group in which a qubit was used
     # group numbers for each gate are incremented by 3 so they don't overlap
     # and different gate types don't go in the same group
     # RZ gates go in (mod 3)=0 groups, R1XY gates go in (mod 3)=1 groups,
@@ -78,7 +98,9 @@ def process_sub_commands(
                 group_available = group_number in groups
                 # is that group later in execution than the
                 # most recent group for an op on that qubit?
-                order_preserved = group_number > qubits2groups[qubit]
+                order_preserved = exec_order_preserved_helper(
+                    qubits2groups, group_number, qubits2groups[qubit]
+                )
                 # is the group size still under the maximum allowed parallel ops?
                 group_size = len(groups[group_number]) if group_number in groups else 0
                 group_not_too_large = group_size < max_parallel_sq_gates

tests/data/qasm/exec_order_two_qubits.qasm

@@ -0,0 +1,19 @@
+OPENQASM 2.0;
+include "qelib1.inc";
+include "hqslib1_dev.inc";
+qreg q[2];
+creg c[2];
+ry(3.5*pi) q[0];
+rx(3.5*pi) q[1];
+ZZ q[0],q[1];
+rx(0.5*pi) q[0];
+barrier q[0],q[1];
+rx(3.5*pi) q[0];
+rz(3.5*pi) q[1];
+rx(1.0*pi) q[1];
+ZZ q[0],q[1];
+ry(0.5*pi) q[0];
+ry(3.5*pi) q[1];
+barrier q[0],q[1];
+measure q[0] -> c[0];
+measure q[1] -> c[1];

tests/test_parallelization.py

@@ -103,3 +103,24 @@ def test_single_qubit_circuit_with_parallel() -> None:
             phir_with_parallel_phirgen["ops"][i]["args"]
             == phir_with_standard_phirgen["ops"][i]["args"]
         )
+
+
+def test_two_qubit_exec_order_preserved() -> None:
+    """Test that the order of gating in preserved in a 2 qubit circuit."""
+    phir = get_phir_json(QasmFile.exec_order_two_qubits, rebase=True)
+    # for this test, verify that the RX gates are NOT parallelized
+    # in the following section of the qasm file (lines 11-13):
+    # rx(3.5*pi) q[0];
+    assert phir["ops"][18] == {
+        "qop": "R1XY",
+        "angles": [[3.5, 0.0], "pi"],
+        "args": [["q", 0]],
+    }
+    # rz(3.5*pi) q[1];
+    assert phir["ops"][20] == {"qop": "RZ", "angles": [[3.5], "pi"], "args": [["q", 1]]}
+    # rx(1.0*pi) q[1];
+    assert phir["ops"][24] == {
+        "qop": "R1XY",
+        "angles": [[1.0, 0.0], "pi"],
+        "args": [["q", 1]],
+    }

tests/test_utils.py

@@ -46,6 +46,7 @@ class QasmFile(Enum):
     rxrz = auto()
     classical_ordering = auto()
     single_qubit_parallel_test = auto()
+    exec_order_two_qubits = auto()
 
 
 class WatFile(Enum):