[Performance] Faster CatFrames.unfolding with padding="same"

[kurtamohler]

Description

Improves the performance of CatFrames.unfolding with padding="same". Running the performance measurement script in the issue description of #2406 shows a speedup of ~70x compared to the previous implementation:

WITHOUT CATFRAMES
Sampling took 0.0016054896002363724 seconds.
WITH CATFRAMES
Sampling took 0.003015774066928619 seconds.

Motivation and Context

close #2406

• I have raised an issue to propose this change (required for new features and bug fixes)

Types of changes

What types of changes does your code introduce? Remove all that do not apply:

• Bug fix (non-breaking change which fixes an issue)

Checklist

Go over all the following points, and put an x in all the boxes that apply.
If you are unsure about any of these, don't hesitate to ask. We are here to help!

• I have read the CONTRIBUTION guide (required)
• My change requires a change to the documentation.
• I have updated the tests accordingly (required for a bug fix or a new feature).
• I have updated the documentation accordingly.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/rl/2407

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

❌ 8 New Failures, 8 Unrelated Failures

As of commit 86f4348 with merge base e82a69f ():

NEW FAILURES - The following jobs have failed:

• Habitat Tests on Linux / tests (3.9, 12.1) / linux-job (gh)
  RuntimeError: Command docker exec -t e5d1c2ce41dcc37ed078b1221ebfdddf146a2212ed2c36325acaa337e8e646ce /exec failed with exit code 139
• Unit-tests on Linux / tests-cpu (3.10) / linux-job (gh)
  test/test_loggers.py::TestWandbLogger::test_log_video
• Unit-tests on Linux / tests-cpu (3.11) / linux-job (gh)
  test/test_loggers.py::TestWandbLogger::test_log_video
• Unit-tests on Linux / tests-cpu (3.12) / linux-job (gh)
  test/test_loggers.py::TestWandbLogger::test_log_video
• Unit-tests on Linux / tests-cpu (3.9) / linux-job (gh)
  test/test_loggers.py::TestWandbLogger::test_log_video
• Unit-tests on Linux / tests-cpu-oldget (3.12) / linux-job (gh)
  test/test_loggers.py::TestWandbLogger::test_log_video
• Unit-tests on Linux / tests-gpu (3.11, 12.1) / linux-job (gh)
  test/test_loggers.py::TestWandbLogger::test_log_video
• Unit-tests on Linux / tests-stable-gpu (3.10, 11.8) / linux-job (gh)
  test/test_loggers.py::TestWandbLogger::test_log_video

FLAKY - The following jobs failed but were likely due to flakiness present on trunk:

• Build Windows Wheels / pytorch/rl (pytorch/rl, python packaging/wheel/relocate.py, test/smoke_test.py, torchrl) / upload / wheel-py3_9-cuda11_8 (gh) (detected as infra flaky with no log or failing log classifier)
• Build Windows Wheels / pytorch/rl (pytorch/rl, python packaging/wheel/relocate.py, test/smoke_test.py, torchrl) / upload / wheel-py3_9-cuda12_1 (gh) (detected as infra flaky with no log or failing log classifier)
• Build Windows Wheels / pytorch/rl (pytorch/rl, python packaging/wheel/relocate.py, test/smoke_test.py, torchrl) / upload / wheel-py3_9-cuda12_4 (gh) (detected as infra flaky with no log or failing log classifier)
• Continuous Benchmark (PR) / CPU Pytest benchmark (gh) (detected as infra flaky with no log or failing log classifier)
• Continuous Benchmark (PR) / GPU Pytest benchmark (gh) (detected as infra flaky with no log or failing log classifier)

BROKEN TRUNK - The following jobs failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• Build Windows Wheels / pytorch/rl (pytorch/rl, python packaging/wheel/relocate.py, test/smoke_test.py, torchrl) / upload / wheel-py3_9-cpu (gh) (trunk failure)
• Libs Tests on Linux / unittests-gym (3.9, 12.1) / linux-job (gh) (trunk failure)
  test/test_libs.py::TestCollectorLib::test_collector_run[device0-GymEnv-env_args0-env_kwargs0]
• Unit-tests on Linux / tests-olddeps (3.8, 11.6) / linux-job (gh) (trunk failure)
  test/test_transforms.py::TestKLRewardTransform::test_kl_lstm

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[vmoens]

Amazing, I'm so grateful for this!
Can you just comment on the 0: indexing?

[vmoens]

Do we need the 0: here?

[kurtamohler]

Oh right, :num_repeats will work, without the 0. I'll update it