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⚡ Bolt: [performance improvement] Convert O(N²) rank lookup to O(N) dictionary in reranker#396

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⚡ Bolt: [performance improvement] Convert O(N²) rank lookup to O(N) dictionary in reranker#396
bashandbone wants to merge 1 commit into
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bolt/reranker-rank-lookup-optimization-4362230007984950645

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@bashandbone

@bashandbone bashandbone commented Jun 15, 2026

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💡 What

Replaced a generator comprehension next(...) used inside an array extension loop in default_reranking_output_transformer with a pre-calculated hash map (rank_map).

🎯 Why

The nested generator comprehension repeatedly iterated over the elements of mapped_scores for each index sequentially, causing an O(N²) time complexity algorithmic bottleneck when iterating over document chunks in a reranking process.

📊 Impact

Reduces the algorithmic evaluation complexity of document reranking assignments strictly from O(N²) to O(N), offering significantly shorter evaluation periods during heavily populated return arrays by leveraging O(1) constant-time dictionary lookups.

🔬 Measurement

The functionality is fully verified by the successful execution of the core tests/unit/providers/reranking/ test suite and standard testing metrics, preserving exact match outputs functionally.


PR created automatically by Jules for task 4362230007984950645 started by @bashandbone

Summary by Sourcery

Enhancements:

  • Replace repeated linear scans over mapped scores with a precomputed dictionary for constant-time batch rank lookup in reranking output transformation.

…ictionary in reranker

What: Replaced a generator comprehension used to look up element ranks during array extension with an explicitly pre-calculated hash map.
Why: The nested generator lookup evaluated linearly within an outer loop, resulting in O(N²) complexity. The pre-calculated hash map provides O(1) constant-time access inside the same loop.
Impact: Reduces the algorithmic time complexity of ranking evaluations from O(N²) down to O(N).
Measurement: Confirmed by test executions within `tests/unit/providers/reranking/`.

Co-authored-by: bashandbone <89049923+bashandbone@users.noreply.github.com>
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sourcery-ai Bot commented Jun 15, 2026

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Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Refactors the reranking output transformer to precompute a rank lookup dictionary, replacing an O(N²) per-item generator-based search with an O(N) hash map lookup while preserving existing behavior and test coverage.

File-Level Changes

Change Details Files
Optimize batch_rank computation in reranking output transformer from O(N²) to O(N) using a precomputed rank map.
  • Keep mapped_scores computation but use its enumeration to build a rank_map of original index to rank (1-based).
  • Replace the per-result generator expression that searched mapped_scores for the matching index with a constant-time rank_map.get lookup using default -1.
  • Add a clarifying comment documenting the complexity improvement from nested lookup to hash map lookup.
src/codeweaver/providers/reranking/providers/base.py

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🤖 Hi @bashandbone, I've received your request, and I'm working on it now! You can track my progress in the logs for more details.

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Hey - I've left some high level feedback:

  • Given that mapped_scores is built from enumerate(results), every i will exist in rank_map, so the -1 default in rank_map.get(i, -1) is redundant; consider using direct indexing (or removing the default) to simplify.
  • The performance comment above rank_map is helpful but a bit verbose; consider tightening it to a brief note about avoiding repeated scans of mapped_scores for clarity.
Prompt for AI Agents
Please address the comments from this code review:

## Overall Comments
- Given that `mapped_scores` is built from `enumerate(results)`, every `i` will exist in `rank_map`, so the `-1` default in `rank_map.get(i, -1)` is redundant; consider using direct indexing (or removing the default) to simplify.
- The performance comment above `rank_map` is helpful but a bit verbose; consider tightening it to a brief note about avoiding repeated scans of `mapped_scores` for clarity.

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🤖 I'm sorry @bashandbone, but I was unable to process your request. Please see the logs for more details.

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