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Chunk Kumo row embeddings - #1015

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@ValterH ValterH commented Sep 28, 2026 •

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Split from #996 to keep each review focused on one behavior or optimization.

On CUDA without gradients, embed context rows once and query rows in balanced passes when the query cells exceed the chunk memory budget. Query passes replay the recorded context state and align with row-attention chunks to preserve single-pass results up to floating-point rounding differences.

The ICL block also releases the label embedding and each layer's full key/value projections earlier.

Depends on #1013. Split from #996; related to #994.

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@RBendias
RBendias marked this pull request as ready for review September 28, 2026 21:49
@ValterH
ValterH force-pushed the mem-opt/1-share-chunk-memory-sizing branch from 96cb79a to 219ebe7 Compare September 28, 2026 22:02
@ValterH
ValterH added this pull request to stack #1020 September 28, 2026 22:08
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Reviewing files that changed from the base of the PR and between 5477284 and dfd4287.

📒 Files selected for processing (3)
  • sdm/models/kumo/tabular/icl.py
  • sdm/models/kumo/tabular/row_embedding.py
  • test/models/kumo/tabular/test_model.py

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📝 Summary

Summary by CodeRabbit

  • New Features
    • Large tabular queries can now be processed in memory-limited passes on supported CUDA systems, reducing peak memory use while preserving prediction results. This applies to both classification and regression, including queries with missing feature values. Queries that fit within available memory continue to be processed in a single pass, and results remain consistent across different pass sizes.

Walkthrough

RowEmbedding selects memory-limited CUDA passes for eligible inputs and reuses frozen cache state across query slices. ICL deletes temporary tensor references and builds the truncated cache entry before calling the query layer. CUDA tests compare output consistency and peak memory.

Changes

Kumo Memory Processing

Layer / File(s) Summary
Pass selection and execution
sdm/models/kumo/tabular/row_embedding.py, test/models/kumo/tabular/test_row_embedding.py, test/models/kumo/tabular/test_model.py
RowEmbedding selects grid-aligned passes when CUDA memory conditions allow, processes context rows before query slices, and freezes cache state between them. CUDA tests compare output consistency and peak memory.

ICL Tensor Lifetimes

Layer / File(s) Summary
Tensor lifetime and cache preparation
sdm/models/kumo/tabular/icl.py
ICL deletes the temporary label embedding after adding it to x. The query-attention path creates a cache entry from truncated key and value tensors before calling the query layer.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~25 minutes

Sequence Diagram(s)

sequenceDiagram
  participant RowEmbedding
  participant PassStarts as _pass_starts
  participant Forward as _forward
  participant Cache
  RowEmbedding->>PassStarts: choose pass boundaries
  PassStarts-->>RowEmbedding: return pass plan
  RowEmbedding->>Forward: process context rows with targets
  RowEmbedding->>Cache: freeze cache
  RowEmbedding->>Forward: process query slices without targets
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Merge Risk: 🔵 Low · up to dfd42

The change appears mergeable with owner awareness, but the exact float16 assertion may make the CUDA test fail on some GPUs even when predictions differ only by rounding.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name Status Explanation Resolution
Docstring Coverage ⚠️ Warning Docstring coverage is 16.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 25 functions across 9 files. Write docstrings for the functions missing them to satisfy the coverage threshold.
✅ Passed checks (4 passed)
Check name Status Explanation
Description check ✅ Passed The description clearly explains the Kumo row-embedding pass optimization, memory behavior, ICL tensor release, and related dependencies.
Title check ✅ Passed The title concisely identifies the main change: chunking Kumo row embeddings.
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.
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@ValterH
ValterH force-pushed the mem-opt/5-chunk-kumo-row-embeddings branch 2 times, most recently from 3131213 to 5d92e2b Compare September 29, 2026 08:50
Base automatically changed from mem-opt/1-share-chunk-memory-sizing to main September 29, 2026 08:53
@ValterH
ValterH force-pushed the mem-opt/5-chunk-kumo-row-embeddings branch from 5d92e2b to a39ce6a Compare September 29, 2026 08:53

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Quiet mode is enabled, so only the most important comments were posted inline. Other review comments are grouped below.

🟡 Other comments (1)
test/models/kumo/tabular/test_row_embedding.py-148-148 (1)

148-148: 🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Replace the exact torch.equal check with a tolerance-based comparison.

The comment in _pass_starts says that passes match a single pass only "up to rare rounding differences in small passes". This test runs under float16 autocast. It then asserts bit-exact equality between the multi-pass output and the forced single-pass output. The result can differ in the last bits when:

  • the GPU architecture differs,
  • the attention kernel selection changes, or
  • the grid alignment has a partial last chunk.

On those systems, the test can fail even though the code is correct. test_row_embedding_passes already uses assert_close. Use it here too, with float16-appropriate tolerances.

Proposed fix
-    assert torch.equal(actual, expected)
+    torch.testing.assert_close(actual, expected, atol=1e-3, rtol=1e-3)

This change is based on the retrieved learning: "avoid exact equality assertions on floating-point values that undergo rounding".

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Review comment at @test/models/kumo/tabular/test_row_embedding.py at line 148:
Replace the bit-exact comparison in the test around `_pass_starts` with a
tolerance-based `torch.testing.assert_close` check using float16-appropriate
tolerances, consistent with `test_row_embedding_passes`.

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Other comments:
Review comments at @test/models/kumo/tabular/test_row_embedding.py:
- Line 148: Replace the bit-exact comparison in the test around `_pass_starts`
with a tolerance-based `torch.testing.assert_close` check using
float16-appropriate tolerances, consistent with `test_row_embedding_passes`.

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📥 Commits

Reviewing files that changed from the base of the PR and between 5d92e2b and 5477284.

📒 Files selected for processing (4)
  • sdm/models/kumo/tabular/icl.py
  • sdm/models/kumo/tabular/row_embedding.py
  • test/models/kumo/tabular/test_model.py
  • test/models/kumo/tabular/test_row_embedding.py

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@ValterH
ValterH removed this pull request from stack #1020 September 29, 2026 09:59
JingangQu and others added 2 commits September 29, 2026 12:33
- Without gradients on CUDA, embed the context rows once and the query
  rows in balanced passes that replay the recorded context state, when
  the query cells would exceed the chunk memory limit.
- Align passes with the chunks of the row attention, so every row runs in
  a chunk of the same size as in a single pass. Passes then match a
  single pass up to rare rounding differences in small passes.
- Free the label embedding and each layer's full key/value early in the
  ICL block.

Signed-off-by: Jingang Qu <jqu@nvidia.com>
@ValterH
ValterH force-pushed the mem-opt/5-chunk-kumo-row-embeddings branch from 5477284 to dfd4287 Compare September 29, 2026 10:33

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3 participants