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⚡ Bolt: Optimize batch rank lookup complexity#371

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bolt-optimize-batch-rank-5058674090919253659
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⚡ Bolt: Optimize batch rank lookup complexity#371
bashandbone wants to merge 1 commit into
mainfrom
bolt-optimize-batch-rank-5058674090919253659

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@bashandbone
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@bashandbone bashandbone commented May 31, 2026

💡 What: Replaced the next(...) generator expression with a precomputed dictionary mapping (rank_map) to perform $O(1)$ lookups.
🎯 Why: The original implementation performed an $O(N)$ generator search inside an $O(N)$ loop, resulting in $O(N^2)$ algorithmic complexity for batch rank assignment. By precomputing the ranks, we avoid scanning the entire list for every single element.
📊 Impact: This drastically reduces overhead, yielding a significantly faster batch reranking process when handling large chunk arrays.
🔬 Measurement: The impact and correctness can be verified by observing default_reranking_output_transformer benchmarks and executing the targeted test suite using uv run pytest tests/unit/providers/reranking/ --no-cov.


PR created automatically by Jules for task 5058674090919253659 started by @bashandbone

Summary by Sourcery

Enhancements:

  • Precompute a rank mapping for reranking results to achieve O(N) batch rank assignment instead of O(N^2).

Co-authored-by: bashandbone <89049923+bashandbone@users.noreply.github.com>
Copilot AI review requested due to automatic review settings May 31, 2026 12:37
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sourcery-ai Bot commented May 31, 2026

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Precomputes a rank mapping dictionary for reranking results to replace repeated linear searches with O(1) lookups, reducing the batch rank assignment from O(N^2) to O(N).

Flow diagram for optimized batch rank lookup in default_reranking_output_transformer

flowchart TD
    A[results list] --> B[Build mapped_scores with enumerate and sort]
    B --> C[Build rank_map from mapped_scores]
    C --> D[Iterate results with enumerate]
    D --> E[Lookup batch_rank using rank_map.get]
    E --> F[Create RerankingResult and extend processed_results]
Loading

File-Level Changes

Change Details Files
Optimize batch rank assignment by precomputing a rank map instead of repeatedly scanning the sorted scores.
  • Introduce rank_map dictionary that maps original indices to their rank positions based on mapped_scores.
  • Update RerankingResult construction to use rank_map.get(i, -1) for batch_rank instead of a generator expression with next().
  • Keep existing sorting and result iteration logic intact while improving per-element lookup complexity.
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:

  • Consider simplifying the inline comment above rank_map to a concise, neutral description (e.g., "Precompute index→rank mapping to avoid repeated scans"), since emojis and marketing-style phrasing can be noisy in core logic.
Prompt for AI Agents
Please address the comments from this code review:

## Overall Comments
- Consider simplifying the inline comment above `rank_map` to a concise, neutral description (e.g., "Precompute index→rank mapping to avoid repeated scans"), since emojis and marketing-style phrasing can be noisy in core logic.

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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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Pull request overview

This PR optimizes the default reranking output transformation by replacing repeated linear rank searches with a precomputed lookup map, reducing rank assignment from O(N²) to O(N).

Changes:

  • Builds a rank_map from sorted scores once.
  • Uses O(1) lookup for each result’s batch_rank.
  • Preserves existing ranking semantics.

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((i, score) for i, score in enumerate(results)), key=lambda x: x[1], reverse=True
)
# ⚡ Bolt: Precompute rank mapping to reduce lookup algorithmic complexity from O(N^2) to O(N)
rank_map = {idx: j + 1 for j, (idx, _) in enumerate(mapped_scores)}
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