Removed _pauli_preprocessed flag from Pattern class functions.

graphix/pattern.py

@@ -43,12 +43,7 @@
 
     from graphix.flow.core import CausalFlow, GFlow, XZCorrections
     from graphix.parameter import ExpressionOrSupportsComplex, ExpressionOrSupportsFloat, Parameter
-    from graphix.sim import (
-        Backend,
-        Data,
-        DensityMatrixBackend,
-        StatevectorBackend,
-    )
+    from graphix.sim import Backend, Data, DensityMatrixBackend, StatevectorBackend
     from graphix.sim.base_backend import _StateT_co
     from graphix.sim.tensornet import TensorNetworkBackend
     from graphix.simulator import _BackendLiteral
@@ -113,7 +108,6 @@ def __init__(
         else:
             self.__input_nodes = list(input_nodes)  # input nodes (list() makes our own copy of the list)
         self.__n_node = len(self.__input_nodes)  # total number of nodes in the graph state
-        self._pauli_preprocessed = False  # flag for `measure_pauli` preprocessing completion
 
         self.__seq = []
         # output nodes are initially a copy input nodes, since none are measured yet
@@ -135,7 +129,6 @@ def add(self, cmd: Command) -> None:
         cmd : :class:`graphix.command.Command`
             MBQC command.
         """
-        self._pauli_preprocessed = False
         if cmd.kind == CommandKind.N:
             self.__n_node += 1
             self.__output_nodes.append(cmd.node)
@@ -149,7 +142,6 @@ def extend(self, *cmds: Command | Iterable[Command]) -> None:
 
         :param cmds: sequences of commands
         """
-        self._pauli_preprocessed = False
         for item in cmds:
             if isinstance(item, Iterable):
                 for cmd in item:
@@ -159,7 +151,6 @@ def extend(self, *cmds: Command | Iterable[Command]) -> None:
 
     def clear(self) -> None:
         """Clear the sequence of pattern commands."""
-        self._pauli_preprocessed = False
         self.__n_node = len(self.__input_nodes)
         self.__seq = []
         self.__output_nodes = list(self.__input_nodes)
@@ -171,7 +162,6 @@ def replace(self, cmds: list[Command], input_nodes: list[int] | None = None) ->
 
         :param input_nodes: optional, list of input qubits (by default, keep the same input nodes as before)
         """
-        self._pauli_preprocessed = False
         if input_nodes is not None:
             self.__input_nodes = list(input_nodes)
         self.clear()
@@ -217,7 +207,6 @@ def compose(
         - Input (and, respectively, output) nodes in the returned pattern have the order of the pattern `self` followed by those of the pattern `other`. Merged nodes are removed.
         - If `preserve_mapping = True` and :math:`|M_1| = |I_2| = |O_2|`, then the outputs of the returned pattern are the outputs of pattern `self`, where the nth merged output is replaced by the output of pattern `other` corresponding to its nth input instead.
         """
-        self._pauli_preprocessed = False
         nodes_p1 = self.extract_nodes() | self.results.keys()  # Results contain preprocessed Pauli nodes
         nodes_p2 = other.extract_nodes() | other.results.keys()
 
@@ -1315,13 +1304,12 @@ def minimize_space(self) -> None:
         if not self.is_standard():
             self.standardize()
         meas_order = None
-        if not self._pauli_preprocessed:
-            try:
-                cf = self.extract_causal_flow()
-            except FlowError:
-                meas_order = None
-            else:
-                meas_order = list(itertools.chain(*reversed(cf.partial_order_layers[1:])))
+        try:
+            cf = self.extract_causal_flow()
+        except FlowError:
+            meas_order = None
+        else:
+            meas_order = list(itertools.chain(*reversed(cf.partial_order_layers[1:])))
         if meas_order is None:
             meas_order = self._measurement_order_space()
         self._reorder_pattern(self.sort_measurement_commands(meas_order))
@@ -1483,7 +1471,7 @@ def perform_pauli_measurements(self, ignore_pauli_with_deps: bool = False) -> No
         """
         if self.input_nodes:
             raise ValueError("Remove inputs with `self.remove_input_nodes()` before performing Pauli presimulation.")
-        measure_pauli(self, copy=False, ignore_pauli_with_deps=ignore_pauli_with_deps)
+        self.__dict__.update(measure_pauli(self, ignore_pauli_with_deps=ignore_pauli_with_deps).__dict__)
 
     def draw_graph(
         self,
@@ -1600,7 +1588,6 @@ def copy(self) -> Pattern:
         result.__input_nodes = self.__input_nodes.copy()
         result.__output_nodes = self.__output_nodes.copy()
         result.__n_node = self.__n_node
-        result._pauli_preprocessed = self._pauli_preprocessed
         result.results = self.results.copy()
         return result
 
@@ -1709,7 +1696,7 @@ def __str__(self) -> str:
         assert_never(self.reason)
 
 
-def measure_pauli(pattern: Pattern, *, copy: bool = False, ignore_pauli_with_deps: bool = False) -> Pattern:
+def measure_pauli(pattern: Pattern, *, ignore_pauli_with_deps: bool = False) -> Pattern:
     """Perform Pauli measurement of a pattern by fast graph state simulator.
 
     Uses the decorated-graph method implemented in graphix.graphsim to perform the measurements in Pauli bases, and then sort remaining nodes back into
@@ -1720,9 +1707,6 @@ def measure_pauli(pattern: Pattern, *, copy: bool = False, ignore_pauli_with_dep
     Parameters
     ----------
     pattern : graphix.pattern.Pattern object
-    copy : bool
-        True: changes will be applied to new copied object and will be returned
-        False: changes will be applied to the supplied Pattern object
     ignore_pauli_with_deps : bool
         Optional (*False* by default).
         If *True*, Pauli measurements with domains depending on other measures are preserved as-is in the pattern.
@@ -1738,14 +1722,14 @@ def measure_pauli(pattern: Pattern, *, copy: bool = False, ignore_pauli_with_dep
     .. seealso:: :class:`graphix.pattern.Pattern.remove_input_nodes`
     .. seealso:: :class:`graphix.graphsim.GraphState`
     """
-    pat = Pattern() if copy else pattern
+    pat = Pattern()
     standardized_pattern = optimization.StandardizedPattern.from_pattern(pattern)
     if not ignore_pauli_with_deps:
         standardized_pattern = standardized_pattern.perform_pauli_pushing()
     output_nodes = set(pattern.output_nodes)
     graph = standardized_pattern.extract_graph()
     graph_state = GraphState(nodes=graph.nodes, edges=graph.edges, vops=standardized_pattern.c_dict)
-    results: dict[int, Outcome] = pat.results
+    results: dict[int, Outcome] = pattern.results
     to_measure, non_pauli_meas = pauli_nodes(standardized_pattern)
     if not to_measure:
         return pattern
@@ -1813,7 +1797,6 @@ def measure_pauli(pattern: Pattern, *, copy: bool = False, ignore_pauli_with_dep
     pat.reorder_output_nodes(standardized_pattern.output_nodes)
     assert pat.n_node == len(graph_state.nodes)
     pat.results = results
-    pat._pauli_preprocessed = True
     return pat