Deprecate provider-specific fake backends,FakeProvider class and related tools in 0.46 #11381

ElePT · 2023-12-07T17:03:03Z

Summary

(1/2) --> This is the first PR of the second step of the FakeBackends refactoring epic in the main branch, it deprecates the snapshot-dependent fake backends as well as the fake provider.

Details and comments

This PR is blocked by:

Add fake generic and modify tests (backport #10266) #11670 (backport of Add fake generic and modify tests #10266)
qiskit-ibm-runtime release including Migrate fake provider base classes from Qiskit qiskit-ibm-runtime#1270 -> to avoid deprecation warnings being raised when using the fake backends in qiskit-ibm-runtime, as this PR directly modifies the fake backend base classes currently shared with runtime. In principle people would use qiskit-ibm-runtime with qiskit 1.0, so it is unlikely that the warning would be raised, but it's a good safeguard to have.

This PR is followed by:

Remove provider-specific fake backends,FakeProvider class and related tools in 1.0 #11376

Related PRs:

qiskit-bot · 2024-01-16T09:24:30Z

One or more of the the following people are requested to review this:

@Qiskit/terra-core
@nkanazawa1989

…e fake backend base classes and special fake backends for testing purposes.

qiskit/providers/fake_provider/fake_backend.py

qiskit/providers/fake_provider/fake_job.py

qiskit/providers/fake_provider/fake_provider.py

qiskit/providers/fake_provider/fake_pulse_backend.py

releasenotes/notes/deprecate-fake-backends-4dd275cf9a30d41f.yaml

Co-authored-by: Kevin Hartman <kevin@hart.mn>

ElePT · 2024-01-30T16:34:43Z

@kevinhartman I've pushed an extended version of the warnings, let me know what you think.

ElePT · 2024-01-30T18:59:37Z

#11670 has been merged, so the deprecation messages now point to an existing alternative :) I'm removing the "on hold" label.

qiskit/providers/fake_provider/fake_provider.py

kevinhartman · 2024-01-30T19:34:35Z

qiskit/providers/fake_provider/fake_pulse_backend.py

@@ -26,6 +28,22 @@ class FakePulseBackend(FakeQasmBackend):

    defs_filename = None

+    def __init__(self):
+        super().__init__()
+        # This is a deprecation warning for the subclasses.


Is this class still used by anything in Qiskit? And, how about FakeBackendV1 which this ultimately uses as a base class? Can all of this be deprecated?

Ah I see, you're doing this in a separate PR it looks like 😄.

Or wait, are you? I'm a bit confused since I would think this file wouldn't have changes at all here since it's part of the V1 hierarchy?

This is confusing, but the V1 base classes (FakeBackendV1, FakePulseBackend, FakeQasmBackend) cannot be deprecated yet because they are used in the "generic" backend version too. The "fake backend alternatives" in #10952 are effectively snapshot-based fake backends with "more generic" names. This was agreed to be the best temporary alternative while BackendV1 is around, the plan is to eventually fully transition to BackendV2 but this will not happen for 1.0.

So now we have the challenge to deprecate ~45 subclasses without deprecating the base classes. This warning is only for the subclasses, and this is why I don't use the decorator here, so that the message doesn't say "FakeBackendV1 is deprecated" but "All fake backend instances based on real device snapshots...". And about the V1 hierarchy, I am taking advantage of the fact that these "V1 alternatives" to fake backends live on the main branch and the deprecations live on 0.46, so the warning would never appear on the non-deprecated alternatives.

Ah okay, thank you! I was missing that subtly 😄.

kevinhartman · 2024-01-30T19:35:52Z

qiskit/providers/fake_provider/fake_pulse_backend.py

+        # This is a deprecation warning for the subclasses.
+        # FakePulseBackend is not deprecated.
+        warnings.warn(
+            message="All fake backend instances based on real device snapshots (`FakeVigo`,"


It might be nice to have this message in the deprecation for FakeBackendV2 as well, since as it is I believe it won't tell users that the classes which inherit from FakeBackendV2 are deprecated.

I tested the warnings locally and they show up in my environment (I also checked when running the unit tests):

Ah, I specifically meant the bit "All fake backend instances based on real device snapshots" might be helpful, since the user might think it's a bug otherwise to get a warning about a base class.

aah sure, that makes sense

I actually realized thanks to that screenshot that the message said "it will be removed Qiskit 1.0", so I updated the removal timeline of all the classes that were missing the "in" in 706de09.

qiskit/providers/fake_provider/fake_mumbai_v2.py

qiskit/providers/fake_provider/fake_provider.py

kevinhartman · 2024-01-30T21:17:34Z

test/python/transpiler/test_target.py

@@ -55,7 +56,9 @@
 class TestTarget(QiskitTestCase):
    def setUp(self):
        super().setUp()
-        self.fake_backend = FakeBackendV2()
+        with warnings.catch_warnings():


Should we assert that this warns instead since we're deprecating now?

kevinhartman · 2024-01-30T21:18:07Z

test/python/transpiler/test_unitary_synthesis.py

@@ -681,7 +686,9 @@ def test_non_overlapping_kak_gates_with_backendv2(self, opt_level):
        qr = QuantumRegister(2)
        circ = QuantumCircuit(qr)
        circ.append(random_unitary(4, seed=1), [1, 0])
-        backend = FakeBackendV2()
+        with warnings.catch_warnings():


Same comment. Assert warns instead?

kevinhartman

LGTM, thanks for doing this!

ElePT added the Changelog: Deprecation Include in "Deprecated" section of changelog label Dec 8, 2023

ElePT added this to the 0.46.0 milestone Dec 8, 2023

This was referenced Dec 11, 2023

Remove provider-specific fake backends,FakeProvider class and related tools in 1.0 #11376

Merged

Add generic Fake Backends and update use in Qiskit unit tests #10954

Closed

ElePT mentioned this pull request Jan 15, 2024

qiskit-ibm-runtime release necessary before qiskit 0.46 release date (Feb 1st 2024) Qiskit/qiskit-ibm-runtime#1317

Closed

ElePT added the on hold Can not fix yet label Jan 16, 2024

ElePT marked this pull request as ready for review January 16, 2024 09:24

ElePT requested review from jyu00 and a team as code owners January 16, 2024 09:24

ElePT mentioned this pull request Jan 26, 2024

Add fake generic and modify tests #10266

Merged

ElePT removed the on hold Can not fix yet label Jan 29, 2024

Deprecate fake provider class and device-specific fake backends. Leav…

c5532d0

…e fake backend base classes and special fake backends for testing purposes.

ElePT force-pushed the deprecate-fake-backends branch from be673e7 to c5532d0 Compare January 29, 2024 18:38

ElePT requested review from nonhermitian and woodsp-ibm as code owners January 29, 2024 18:38

Fix lint

a4e4f6a

ElePT added the on hold Can not fix yet label Jan 29, 2024

kevinhartman reviewed Jan 30, 2024

View reviewed changes

ElePT and others added 3 commits January 30, 2024 16:29

Apply suggestions from Kevin's code review

592e93b

Co-authored-by: Kevin Hartman <kevin@hart.mn>

Move warning to after construction

a89d95c

Adjust warnings

8e489ae

Deprecate fake backend V2

1508e8f

ElePT removed the on hold Can not fix yet label Jan 30, 2024

Reno fix

04f389f

kevinhartman reviewed Jan 30, 2024

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qiskit/providers/fake_provider/fake_mumbai_v2.py Show resolved Hide resolved

ElePT commented Jan 30, 2024

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qiskit/providers/fake_provider/fake_provider.py Outdated Show resolved Hide resolved

Update copyright

7fd1e25

kevinhartman reviewed Jan 30, 2024

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ElePT added 2 commits January 30, 2024 22:19

Make FakeBackendV2 message more specific

cf830b4

Fix removal timeline

706de09

kevinhartman approved these changes Jan 30, 2024

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kevinhartman enabled auto-merge January 30, 2024 22:25

kevinhartman added this pull request to the merge queue Jan 30, 2024

Merged via the queue into Qiskit:stable/0.46 with commit 3ca9882 Jan 31, 2024
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Deprecate provider-specific fake backends,FakeProvider class and related tools in 0.46 #11381

Deprecate provider-specific fake backends,FakeProvider class and related tools in 0.46 #11381

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Deprecate provider-specific fake backends,FakeProvider class and related tools in 0.46 #11381

Deprecate provider-specific fake backends,FakeProvider class and related tools in 0.46 #11381

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ElePT commented Dec 7, 2023 • edited

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ElePT commented Dec 7, 2023 •

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