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Align DASC numeric validation with scalar API - #2397

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kaix-nv merged 2 commits into
feature/dasc-state-sparsity-review-validation-sourcefrom
feature/dasc-state-sparsity-review-real-scalars
Sep 11, 2026
Merged

kaix-nv merged 2 commits into
feature/dasc-state-sparsity-review-validation-sourcefrom
feature/dasc-state-sparsity-review-real-scalars

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@kaix-nv kaix-nv commented Sep 11, 2026

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Summary

Addresses both Claude findings on #2396 while retaining CodeRabbit’s oversized-integer fix:

  • match the annotated scalar-float API by accepting numbers.Real inputs, including NumPy real scalars
  • reject all tensor objects before scalar conversion, so multi-element tensors cannot leak RuntimeError
  • keep OverflowError normalization for oversized integer inputs
  • remove the tensor-scalar compatibility claim and restore the original scalar conversion
  • cover multi-element tensors through both exported public entry points

Validation

  • focused DASC suite: 46 passed, 1 optional Megatron skip
  • pre-commit hooks on all three changed files
  • signed commit with DCO sign-off

Summary by CodeRabbit

  • Bug Fixes
    • Improved validation for decay-analysis inputs by requiring real-number values for epsilon and static gate parameters.
    • Invalid non-numeric and tensor-based inputs are now rejected consistently, including zero-dimensional tensor values.
    • Improved numerical consistency when calculating decay horizons by preserving CPU double-precision behavior.
    • Added clearer safeguards against invalid or unsupported input types before analysis calculations are performed.

Signed-off-by: kaix-nv <kaix@nvidia.com>
@kaix-nv
kaix-nv requested review from a team as code owners September 11, 2026 04:26
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kaix-nv requested review from realAsma and removed request for a team September 11, 2026 04:26
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kaix-nv commented Sep 11, 2026

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/claude review

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kaix-nv commented Sep 11, 2026

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@coderabbitai full review

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  • modelopt/torch/sparsity/state_sparsity/config.py
  • modelopt/torch/sparsity/state_sparsity/policy.py
  • tests/unit/torch/sparsity/state_sparsity/test_dasc.py

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  • modelopt/torch/sparsity/state_sparsity/config.py
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📝 Walkthrough

Walkthrough

The change tightens decay-analysis input validation, rejects tensor-valued epsilon and static gate inputs, uses explicit CPU float64 tensor construction, and updates tests for the revised contract.

Changes

State sparsity validation

Layer / File(s) Summary
Decay-analysis argument validation
modelopt/torch/sparsity/state_sparsity/config.py, tests/unit/torch/sparsity/state_sparsity/test_dasc.py
Validation now requires real-number epsilon and static_gate_input values before applying finite and range checks. Tests cover invalid tensor-valued inputs.
Horizon epsilon construction
modelopt/torch/sparsity/state_sparsity/policy.py, tests/unit/torch/sparsity/state_sparsity/test_dasc.py
Horizon computation now uses torch.tensor for the CPU float64 epsilon scalar. Tests no longer require zero-dimensional tensor scalars to be accepted.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to c74fa

Horizon computation now keeps epsilon on CPU regardless of PyTorch's configured default device, so the prior runtime device mismatch is resolved.

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✅ Passed checks (6 passed)
Check name Status Explanation
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.
Title check ✅ Passed The title clearly and concisely describes the main change: aligning DASC numeric validation with the scalar API.
Docstring Coverage ✅ Passed Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 7 functions across 3 files.
Linked Issues check ✅ Passed Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check ✅ Passed Check skipped because no linked issues were found for this pull request.
Security Anti-Patterns ✅ Passed No listed security anti-pattern is introduced. The authoritative diff contains only two ModelOpt Python files and one test file; it adds numeric validation and replaces torch.as_tensor with `torch.t…
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Inline comments:
In `@modelopt/torch/sparsity/state_sparsity/policy.py`:
- Line 125: Update the tensor construction in the horizons calculation to
explicitly place the epsilon scalar on the CPU, matching the device used for
decay and avoiding default-device mismatches.

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  • modelopt/torch/sparsity/state_sparsity/config.py
  • modelopt/torch/sparsity/state_sparsity/policy.py
  • tests/unit/torch/sparsity/state_sparsity/test_dasc.py

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Comment thread modelopt/torch/sparsity/state_sparsity/policy.py Outdated

decay = -torch.exp(a_log_cpu) * F.softplus(dt_bias_cpu + static_gate_input)
horizons = torch.log(torch.as_tensor(epsilon, device="cpu", dtype=torch.float64)) / decay
horizons = torch.log(torch.tensor(epsilon, dtype=torch.float64)) / decay

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[IMPORTANT Compatibility] This "restore the original scalar conversion" also drops the explicit device="cpu" pin, which is a separate concern from the tensor-rejection change.

What: torch.tensor(...) is a factory function and therefore honors torch.set_default_device(). Under torch.set_default_device("cuda") this allocates the epsilon scalar on CUDA, while decay two lines above is deliberately pinned to CPU (a_log.detach().to(device="cpu", ...)). A 0-dim CUDA tensor divided by a multi-element CPU tensor is not covered by PyTorch's CPU-scalar promotion rule, so the division raises RuntimeError: Expected all tensors to be on the same device....

Why it matters: the function's docstring promises "one static retention horizon per GDN head in CPU float64", and the previous torch.as_tensor(epsilon, device="cpu", ...) guaranteed that regardless of ambient global state. torch.set_default_device("cuda") is a real pattern in this repo (examples/deepseek/deepseek_v4/ptq.py:274), and this failure mode is invisible in the unit tests, which never set a default device.

Fix: now that _validate_analysis_arguments guarantees epsilon is a finite numbers.Real in (0, 1), no tensor is needed at all — math.log gives a device-free Python float, and float / tensor dispatches to the tensor's __rtruediv__:

Suggested change
horizons = torch.log(torch.tensor(epsilon, dtype=torch.float64)) / decay
horizons = math.log(epsilon) / decay

This is device-independent by construction and removes a per-call tensor allocation. It needs import math at the top of policy.py if not already present.

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Fixed in #2398 with the suggested device-free math.log(epsilon) calculation. Added a regression using a non-CPU ambient torch.device context to assert that the documented CPU output contract is preserved.

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✅ Action performed

Full review finished.

Comment on lines 44 to 57
try:
epsilon_is_valid = math.isfinite(epsilon) and 0.0 < epsilon < 1.0
epsilon_is_valid = (
isinstance(epsilon, Real) and math.isfinite(epsilon) and 0.0 < epsilon < 1.0
)
except (TypeError, ValueError, OverflowError):
epsilon_is_valid = False
if not epsilon_is_valid:
raise ValueError("epsilon must be finite and in (0, 1)")

try:
static_gate_input_is_valid = math.isfinite(static_gate_input)
static_gate_input_is_valid = isinstance(static_gate_input, Real) and math.isfinite(
static_gate_input
)
except (TypeError, ValueError, OverflowError):

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[SUGGESTION] Two small follow-ups on the new numbers.Real gate — both non-blocking.

  1. bool passes as Real. boolintIntegralReal, so static_gate_input=True is silently accepted and flows through as 1.0 rather than being rejected as a type error. epsilon is incidentally saved by the 0.0 < epsilon < 1.0 range check (True == 1), but that's coincidence, not intent. validate_wmax_candidates a few lines below already establishes this file's convention of excluding bools explicitly (isinstance(value, bool) or not isinstance(value, int)), so it's worth being consistent:

    epsilon_is_valid = (
        isinstance(epsilon, Real)
        and not isinstance(epsilon, bool)
        and math.isfinite(epsilon)
        and 0.0 < epsilon < 1.0
    )
  2. The except clauses are now wider than reachable. With isinstance(..., Real) short-circuiting first, math.isfinite only ever sees a value that implements __float__ (the numbers.Real ABC requires it), so TypeError/ValueError are no longer reachable here — OverflowError (the 10**1000 case) is the only live path. Narrowing to except OverflowError: documents exactly which input class needs normalization and keeps the handler from quietly swallowing a future real bug.

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Both suggestions are fixed in #2398. bool is explicitly excluded for epsilon and static_gate_input, tests cover both public paths, and the handlers now catch only the reachable OverflowError case.

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Claude review — 1 IMPORTANT, 1 SUGGESTION

Scope: full review. All 3 changed files (+15/-20) reviewed: modelopt/torch/sparsity/state_sparsity/config.py, modelopt/torch/sparsity/state_sparsity/policy.py, tests/unit/torch/sparsity/state_sparsity/test_dasc.py. Nothing deliberately skipped.

Findings

  • CRITICAL: 0
  • IMPORTANT: 1policy.py:125 drops the explicit device="cpu" pin
  • SUGGESTION: 1config.py:44-57 bool passes as Real; except clauses now wider than reachable

Most impactful

Reverting torch.as_tensor(epsilon, device="cpu", dtype=torch.float64) to torch.tensor(epsilon, dtype=torch.float64) bundles two independent changes: dropping as_tensor (correct — tensors are now rejected upstream, so it is no longer needed) and dropping the explicit CPU pin (an unintended regression). torch.tensor is a factory function and honors torch.set_default_device(), so under torch.set_default_device("cuda") the epsilon scalar lands on CUDA while decay is deliberately CPU-pinned one line earlier. A 0-dim CUDA tensor divided by a multi-element CPU tensor falls outside PyTorch's CPU-scalar promotion rule and raises a device-mismatch RuntimeError — contradicting the function's documented "CPU float64" contract. That global-device pattern is in use in this repo (examples/deepseek/deepseek_v4/ptq.py:274), and no unit test sets a default device, so this is silent in CI.

Since validation now guarantees epsilon is a finite Real in (0, 1), math.log(epsilon) / decay is the cleaner fix — device-free by construction and one fewer tensor allocation per call. math is already imported at policy.py:22, so it is a one-line drop-in.

What looks right

  • Tensor rejection is sound. torch.Tensor is not registered with the numbers ABCs, so isinstance(x, Real) rejects every tensor — including 0-dim ones — before any scalar conversion. That genuinely closes the multi-element RuntimeError leak rather than papering over it, which is the right root-cause fix.
  • numbers.Real widening matches the annotated API. NumPy real scalars register with Real, so np.float64/np.float32 epsilon values are accepted as intended, and the OverflowError normalization for 10**1000 is preserved.
  • Config path unaffected. validate_epsilon/validate_static_gate_input are mode="after" validators, so they receive an already-coerced Python float; the new isinstance gate cannot reject previously-valid DASCConfig inputs. No modelopt_state schema or checkpoint-compat impact.
  • Removing test_analysis_accepts_tensor_scalar_arguments is appropriate. It required type: ignore[arg-type] against a float-annotated parameter, i.e. it pinned behavior that was never part of the public contract, and the base branch is an unreleased feature branch — no user-facing break.
  • New test coverage hits both public entry points (analyze_gdn_decay and compute_gdn_decay_horizons) for both arguments.

Risk

Low. Tightly scoped validation change with no mode-registration, state-schema, or export surface touched. The one IMPORTANT finding is a latent device-placement regression that only fires under a non-default global device — worth fixing before merge, but it does not affect the default path.

🤖 Generated with Claude Code

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2026-09-11 04:50 UTC

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.78%. Comparing base (487de7a) to head (e6da8d5).
⚠️ Report is 1 commits behind head on feature/dasc-state-sparsity-review-validation-source.

Additional details and impacted files
@@                                    Coverage Diff                                    @@
##           feature/dasc-state-sparsity-review-validation-source    #2397       +/-   ##
=========================================================================================
+ Coverage                                                 68.76%   78.78%   +10.02%     
=========================================================================================
  Files                                                       548      548               
  Lines                                                     64243    64243               
=========================================================================================
+ Hits                                                      44174    50615     +6441     
+ Misses                                                    20069    13628     -6441     
Flag Coverage Δ
examples-diffusers 20.81% <25.00%> (+0.01%) ⬆️
examples-gpt-oss 13.39% <25.00%> (+<0.01%) ⬆️
examples-hf_ptq 21.78% <25.00%> (+0.01%) ⬆️
examples-llm_distill 13.46% <25.00%> (+<0.01%) ⬆️
examples-llm_eval 17.25% <25.00%> (+<0.01%) ⬆️
examples-llm_qat 17.59% <25.00%> (+0.04%) ⬆️
examples-llm_sparsity 15.94% <25.00%> (+<0.01%) ⬆️
examples-specdec_bench 13.14% <25.00%> (+<0.01%) ⬆️
examples-speculative_decoding 17.67% <25.00%> (+<0.01%) ⬆️
examples-torch_trt 15.15% <25.00%> (+<0.01%) ⬆️
gpu 58.35% <25.00%> (+37.43%) ⬆️
regression 15.15% <25.00%> (+<0.01%) ⬆️
unit 57.47% <100.00%> (+<0.01%) ⬆️

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## Summary

Addresses every finding on #2397:

- compute the scalar log with `math.log`, avoiding ambient PyTorch
default-device allocation entirely
- explicitly reject booleans despite their `numbers.Real` inheritance
- narrow normalization handlers to the reachable oversized-integer
`OverflowError`
- add boolean regressions through both public APIs
- add a CPU-result regression under a non-CPU ambient default-device
context

## Validation

- focused DASC suite: 51 passed, 1 optional Megatron skip
- pre-commit hooks on all changed files
- signed commit with DCO sign-off

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Bug Fixes**
- Improved validation for sparsity analysis arguments, including
rejection of boolean values.
  - Preserved expected error handling for invalid or non-finite inputs.
- Ensured decay horizon calculations work correctly regardless of the
ambient PyTorch device.

- **Tests**
- Expanded coverage for invalid boolean arguments and CPU-based horizon
computation.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Signed-off-by: kaix-nv <kaix@nvidia.com>
@kaix-nv
kaix-nv merged commit 2f033a1 into feature/dasc-state-sparsity-review-validation-source Sep 11, 2026
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