Arm backend: Minimal example of pruning

[gggekov]

Explain how to prune a NN and the associated uplift in performance when running on the Ethos-U NPU.

cc @freddan80 @per @zingo @oscarandersson8218 @digantdesai

[pytorch-bot]

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❌ 47 New Failures, 3 Unrelated Failures

As of commit f6037a4 with merge base b91987e ():

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FLAKY - The following job failed but was likely due to flakiness present on trunk:

• pull / unittest / linux / linux-job (gh) (similar failure)
  exir/backend/test/test_lowered_backend_module.py::TestBackendAPI::test_emit_nested_lowered_backend_module

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

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

• pull / test-setup-linux-gcc / linux-job (gh) (trunk failure)
• pull / unittest-editable / linux / linux-job (gh) (trunk failure)
  exir/backend/test/test_lowered_backend_module.py::TestBackendAPI::test_emit_nested_lowered_backend_module

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[Copilot]

Pull Request Overview

This PR introduces a comprehensive tutorial on neural network pruning for the Arm Ethos-U NPU, demonstrating how to prune a model and measure the resulting performance improvements. The example uses a simple MNIST classifier and shows the complete workflow from training to deployment.

Key changes:

• Adds a Jupyter notebook tutorial demonstrating pruning workflow with PyTorch and ExecuTorch
• Updates performance monitoring to track MAC and Weight Decoder activity for Ethos-U85
• Shows 3x+ inference speedup and significant memory reduction through pruning

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 7 comments.

File	Description
examples/arm/pruning_minimal_example.ipynb	Complete tutorial notebook showing how to prune a neural network, quantize it, and deploy to Ethos-U NPU with performance analysis
examples/arm/executor_runner/arm_perf_monitor.cpp	Adds MAC_ACTIVE and WD_ACTIVE PMU counter tracking for Ethos-U85 to support detailed performance analysis

Comments suppressed due to low confidence (1)

examples/arm/pruning_minimal_example.ipynb:1

• The flag '--debug-force-regor' appears to contain a typo. Verify if this should be '--debug-force-regor' or if it's a misspelling of a valid flag like '--debug-force-regen' or '--debug-force-reorder'.

{

---

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[Copilot]

The import 'DataLoader' is duplicated on lines 54 and 58. Remove the duplicate import from line 58.

Suggested change

	"from torch.utils.data import DataLoader, Subset\n",
	"from torch.utils.data import Subset\n",

[gggekov]

Done.

[zingo]

@gggekov the label "topic: not user facing" is not used anymore so no need to set it it was replaced with "release notes: arm" or "release notes: none"

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