Cpp check nodes (#420)

* add logical node property

* remove unused and untested functions

* rename boundary nodes as logical nodes (if associated with a logical)

* fix issues

* linting

* add graph conversion

* rename old file

* Create pymatching_decoder.py (#415)

Creates a matching object which can be used to decode a counts string via the method process.

* linting

* remove old matching code and tests

* remove old matching code and tests

* remove old imports

* fix fault id issue

* standardize stim code circuit

* get rid of measured_logicals

* remove measuremed_logicals

* remove css decoding graph

* remove css decoding graph

* add graph conversions

* make matching work for non-stim

* add matching tests

* convert to edge graph only when needed

* black

* update doc string

* correct logical nodes

* 2 qubit paulis for cx gates

* extend beyond cx

* allow default check nodes to be used

* rename pymatching decoder

* add cpp check_nodes

* lint

* fix building

* correct path

* add is_cluster_neutral

* fix issues

* fix is_cluster_neutral

* remove legacy methods

* add detail to error messages

* fix extra logicals

* fix minimals

* add detail to message"
"

* thing

* initialize frustration

* initialize frustration

* initialize frustration

* limit loop

* limit loop

* limit loop

* limit loop

* limit loop

* fun stuff

* Revert "limit loop"

This reverts commit 8036e3c.

* revert to 8036e3c

* undo reformatting

* add heavy-hex decoder test

* add heavy-hex decoder test

* add heavy-hex decoder test

* add heavy-hex decoder test

* add heavy-hex decoder test

* linting

---------

Co-authored-by: Bence Hetényi <[email protected]>

CMakeLists.txt

@@ -60,5 +60,9 @@ set(ANALYSIS_BINDINGS_SRC "src/qiskit_qec/analysis/bindings/analysis_bindings.cp
 pybind11_add_module(_c_analysis ${ANALYSIS_BINDINGS_SRC})
 target_link_libraries(_c_analysis PRIVATE libanalysis)
 
+set(CIRCUITS_BINDINGS_SRC "src/qiskit_qec/circuits/bindings/circuits_bindings.cpp")
+pybind11_add_module(_c_circuits ${CIRCUITS_BINDINGS_SRC})
+target_link_libraries(_c_circuits PRIVATE libcircuits)
+
 
 

setup.py

@@ -177,13 +177,18 @@ def build_extension(self, ext: CMakeExtension) -> None:
     python_requires=">=3.8",
     include_package_data=True,
     install_requires=(REQUIREMENTS,),
-    ext_modules=[CMakeExtension("qiskit_qec.analysis._c_analysis")],
+    ext_modules=[
+        CMakeExtension("qiskit_qec.circuits._c_circuits"),
+        CMakeExtension("qiskit_qec.analysis._c_analysis"),
+    ],
     packages=find_packages(
         where="src",
         exclude=[
             "test*",
             "src/qiskit_qec/analysis/bindings*",
             "src/qiskit_qec/analysis/intern*",
+            "src/qiskit_qec/circuits/bindings*",
+            "src/qiskit_qec/circuits/intern*",
             "src/qiskit_qec/codes/codebase/data*",
         ],
     ),

src/qiskit_qec/CMakeLists.txt

@@ -1 +1,2 @@
-add_subdirectory(analysis)
+add_subdirectory(analysis)
+add_subdirectory(circuits)

src/qiskit_qec/circuits/CMakeLists.txt

@@ -0,0 +1,28 @@
+# Code circuit library
+cmake_minimum_required(VERSION 3.12)
+project(Circuits)
+
+set(CIRCUITS_SRC
+    intern/arctools.cpp
+
+    arctools.h
+)
+
+add_library(libcircuits
+    STATIC
+    ${CIRCUITS_SRC}
+)
+
+target_include_directories(libcircuits
+    PUBLIC
+    "${CMAKE_CURRENT_SOURCE_DIR}"
+)
+
+if (NOT (MSVC))
+    target_compile_options(libcircuits PRIVATE -fno-strict-aliasing -fPIC ${ARCH_OPT})
+else ()
+    target_compile_options(libcircuits PRIVATE -fPIC ${ARCH_OPT})
+endif ()
+
+# Set prefix to "" since lib is already in project name
+set_target_properties(libcircuits PROPERTIES PREFIX "")

src/qiskit_qec/circuits/arctools.h

@@ -0,0 +1,26 @@
+#ifndef __ArcTools__
+#define __ArcTools__
+
+#include<vector>
+#include<tuple>
+#include<map>
+#include <set>
+
+std::vector<int> check_nodes(
+    std::vector<std::tuple<int, int, int, bool>> nodes, bool ignore_extra_logicals, bool minimal,
+    std::map<std::tuple<int, int>, std::set<int>> cycle_dict,
+    std::vector<std::tuple<int, int>> link_graph,
+    std::map<int, std::vector<int>> link_neighbors,
+    std::vector<int> z_logicals
+    );
+
+bool is_cluster_neutral(
+    std::vector<std::tuple<int, int, int, bool>> nodes, bool ignore_extra_logicals, bool minimal,
+    std::map<std::tuple<int, int>, std::set<int>> cycle_dict,
+    std::vector<std::tuple<int, int>> link_graph,
+    std::map<int, std::vector<int>> link_neighbors,
+    std::vector<int> z_logicals,
+    bool linear
+    );
+
+#endif

src/qiskit_qec/circuits/bindings/circuits_bindings.cpp

@@ -0,0 +1,12 @@
+#include "arctools.h"
+#include <pybind11/pybind11.h>
+#include <pybind11/stl.h>
+
+namespace py = pybind11;
+
+PYBIND11_MODULE(_c_circuits, module)
+{
+  module.doc() = "qiskit-qec code circuit extensions";
+  module.def("_c_check_nodes", &check_nodes, "check_nodes in C++");
+  module.def("_c_is_cluster_neutral", &is_cluster_neutral, "is_cluster_neutral in C++");
+}

src/qiskit_qec/circuits/code_circuit.py

@@ -53,23 +53,15 @@ def string2nodes(self, string, **kwargs):
         pass
 
     @abstractmethod
-    def measured_logicals(self):
-        """
-        Returns a list of logical operators, each expressed as a list of qubits for which
-        the parity of the final readouts corresponds to the raw logical readout.
-        """
-        pass
-
-    @abstractmethod
-    def check_nodes(self, nodes, ignore_extra_boundary=False, minimal=False):
+    def check_nodes(self, nodes, ignore_extra_logical=False, minimal=False):
         """
         Determines whether a given set of nodes are neutral. If so, also
         determines any additional logical readout qubits that would be
         flipped by the errors creating such a cluster and how many errors
         would be required to make the cluster.
         Args:
             nodes (list): List of nodes, of the type produced by `string2nodes`.
-            ignore_extra_boundary (bool): If `True`, undeeded boundary nodes are
+            ignore_extra_logical (bool): If `True`, undeeded logical nodes are
             ignored.
             minimal (bool): Whether output should only reflect the minimal error
             case.

src/qiskit_qec/circuits/css_code.py

@@ -183,16 +183,6 @@ def _get_code_properties(self):
             self.z_stabilizers = self.code.z_stabilizers
             self.logical_x = self.code.logical_x
             self.logical_z = self.code.logical_z
-        # for the unionfind decoder
-        self.css_x_logical = self.logical_x
-        self.css_z_logical = self.logical_z
-
-    def measured_logicals(self):
-        if self.basis == "x":
-            measured_logicals = self.logical_x
-        else:
-            measured_logicals = self.logical_z
-        return measured_logicals
 
     def _prepare_initial_state(self, qc, qregs, state):
         if state[0] == "1":
@@ -289,7 +279,7 @@ def string2raw_logicals(self, string):
         log_outs = string2logical_meas(string, self.logicals, self.circuit["0"].clbits)
         return log_outs
 
-    def check_nodes(self, nodes, ignore_extra_boundary=False, minimal=False):
+    def check_nodes(self, nodes, ignore_extra_logical=False, minimal=False):
         raise NotImplementedError
 
     def is_cluster_neutral(self, atypical_nodes):

src/qiskit_qec/circuits/extensions.py

@@ -0,0 +1,42 @@
+# This code is part of Qiskit.
+#
+# (C) Copyright IBM 2021.
+#
+# This code is licensed under the Apache License, Version 2.0. You may
+# obtain a copy of this license in the LICENSE.txt file in the root directory
+# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
+#
+# Any modifications or derivative works of this code must retain this
+# copyright notice, and modified files need to carry a notice indicating
+# that they have been altered from the originals.
+# pylint: disable=unused-import
+
+"""Code circuit extensions"""
+
+import logging  # for logging!
+
+logger = logging.getLogger(__name__)
+
+# Load extensions if available and set appriate indicator flags
+
+try:
+    from qiskit_qec.analysis._c_circuits import _c_check_nodes
+
+    C_CHECK_NODES = True
+except ImportError as import_error:
+    logger.exception(  # pylint: disable=logging-fstring-interpolation
+        f"from qiskit_qec.analysis._c_circuits import _c_check_nodes \
+            failed, raising {import_error}"
+    )
+    C_CHECK_NODES = False
+
+try:
+    from qiskit_qec.analysis._c_circuits import _c_is_cluster_neutral
+
+    C_IS_CLUSTER_NEUTRAL = True
+except ImportError as import_error:
+    logger.exception(  # pylint: disable=logging-fstring-interpolation
+        f"from qiskit_qec.analysis._c_circuits import _c_is_cluster_neutral \
+            failed, raising {import_error}"
+    )
+    C_IS_CLUSTER_NEUTRAL = False