Add refresh method to fake backends (#1740)

* added refresh method

* added BackendEncoder

* added logging

* style fixes

* linter fixes

* linter fixes

* added test

* uncomment

* updated refresh func

* linter fixes

* style fixes

* added release note

* upgrade message update

* updated the docstring

* fixed indentation

* Update qiskit_ibm_runtime/fake_provider/fake_backend.py

---------

Co-authored-by: Kevin Tian <kevin.tian@ibm.com>
Co-authored-by: Kevin Tian <kt474@cornell.edu>

qiskit_ibm_runtime/fake_provider/fake_backend.py

@@ -14,7 +14,7 @@
 """
 Base class for dummy backends.
 """
-
+import logging
 import warnings
 import collections
 import json
@@ -40,9 +40,13 @@
 from qiskit.providers.basic_provider import BasicSimulator
 
 from qiskit_ibm_runtime.utils.backend_converter import convert_to_target
+from .. import QiskitRuntimeService
+from ..utils.backend_encoder import BackendEncoder
 
 from ..utils.deprecation import issue_deprecation_msg
 
+logger = logging.getLogger(__name__)
+
 
 class _Credentials:
     def __init__(self, token: str = "123456", url: str = "https://") -> None:
@@ -458,6 +462,65 @@ def _get_noise_model_from_backend_v2(  # type: ignore
 
         return noise_model
 
+    def refresh(self, service: QiskitRuntimeService) -> None:
+        """Update the data files from its real counterpart
+
+        This method pulls the latest backend data files from their real counterpart and
+        overwrites the corresponding files in the local installation:
+        *  ../fake_provider/backends/{backend_name}/conf_{backend_name}.json
+        *  ../fake_provider/backends/{backend_name}/defs_{backend_name}.json
+        *  ../fake_provider/backends/{backend_name}/props_{backend_name}.json
+
+        The new data files will persist through sessions so the files will stay updated unless they
+         are manually reverted locally or when qiskit-ibm-runtime is upgraded/reinstalled.
+
+        Args:
+            service: A :class:`QiskitRuntimeService` instance
+
+        Raises:
+            Exception: If the real target doesn't exist or can't be accessed
+        """
+
+        version = self.backend_version
+        prod_name = self.backend_name.replace("fake", "ibm")
+        try:
+            backends = service.backends(prod_name)
+            real_backend = backends[0]
+
+            real_props = real_backend.properties()
+            real_config = real_backend.configuration()
+            real_defs = real_backend.defaults()
+
+            if real_props:
+                new_version = real_props.backend_version
+
+                if new_version > version:
+                    props_path = os.path.join(self.dirname, self.props_filename)
+                    with open(props_path, "w", encoding="utf-8") as fd:
+                        fd.write(json.dumps(real_props.to_dict(), cls=BackendEncoder))
+
+                    if real_config:
+                        config_path = os.path.join(self.dirname, self.conf_filename)
+                        config_dict = real_config.to_dict()
+                        with open(config_path, "w", encoding="utf-8") as fd:
+                            fd.write(json.dumps(config_dict, cls=BackendEncoder))
+
+                    if real_defs:
+                        defs_path = os.path.join(self.dirname, self.defs_filename)
+                        with open(defs_path, "w", encoding="utf-8") as fd:
+                            fd.write(json.dumps(real_defs.to_dict(), cls=BackendEncoder))
+
+                    logger.info(
+                        "The backend %s has been updated from {version} to %s version.",
+                        self.backend_name,
+                        real_props.backend_version,
+                    )
+                else:
+                    logger.info("There are no available new updates for %s.", self.backend_name)
+
+        except Exception as ex:
+            logger.info("The refreshing of %s has failed: %s", self.backend_name, str(ex))
+
 
 class FakeBackend(BackendV1):
     """This is a dummy backend just for testing purposes."""

qiskit_ibm_runtime/utils/backend_encoder.py

@@ -0,0 +1,36 @@
+# This code is part of Qiskit.
+#
+# (C) Copyright IBM 2024.
+#
+# 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.
+
+"""Utilities for working with IBM Quantum backends."""
+import json
+from datetime import datetime
+from typing import Any
+
+from qiskit.circuit import ParameterExpression
+
+
+class BackendEncoder(json.JSONEncoder):
+    """A json encoder for qobj"""
+
+    def default(self, obj: Any) -> Any:  # pylint: disable=arguments-differ
+        """Default encoding"""
+        # Convert numpy arrays:
+        if hasattr(obj, "tolist"):
+            return obj.tolist()
+        # Use Qobj complex json format:
+        if isinstance(obj, complex):
+            return [obj.real, obj.imag]
+        if isinstance(obj, ParameterExpression):
+            return float(obj)
+        if isinstance(obj, datetime):
+            return obj.isoformat()
+        return json.JSONEncoder.default(self, obj)

release-notes/unreleased/1740.upgrade.rst

@@ -0,0 +1,4 @@
+The instances of :class:`FakeBackend` can now be updated from
+their real counterpart using the :meth:`FakeBackendV2.refresh`.
+To pull the latest real backend data files, access permission is
+required.

test/integration/test_fake_backends.py

@@ -36,7 +36,7 @@
     FakeSherbrooke,
     FakePrague,
 )
-from ..ibm_test_case import IBMTestCase
+from ..ibm_test_case import IBMTestCase, IBMIntegrationTestCase
 
 FAKE_PROVIDER_FOR_BACKEND_V2 = FakeProviderForBackendV2()
 FAKE_PROVIDER = FakeProvider()
@@ -171,3 +171,20 @@ def test_non_cx_tests(self):
         self.assertIsInstance(backend.target.operation_from_name("cz"), CZGate)
         backend = FakeSherbrooke()
         self.assertIsInstance(backend.target.operation_from_name("ecr"), ECRGate)
+
+
+class TestRefreshFakeBackends(IBMIntegrationTestCase):
+
+    @classmethod
+    def setUpClass(cls):
+        # pylint: disable=arguments-differ
+        # pylint: disable=no-value-for-parameter
+        super().setUpClass()
+
+    def test_refresh_method(self):
+        """Test refresh method"""
+        old_backend = FakeSherbrooke()
+        with self.assertLogs("qiskit_ibm_runtime", level="INFO"):
+            old_backend.refresh(self.service)
+        new_backend = FakeSherbrooke()
+        self.assertGreaterEqual(old_backend.backend_version, new_backend.backend_version)