perf: optimize value swap in BTreeMap

[maksymar]

This PR optimizes the value update mechanism in BTreeMap by introducing a dedicated method for replacing values without touching the keys.

[github-actions]

canbench 🏋 (dir: ./benchmarks/compare) e26098d 2025-06-04 15:08:33 UTC

✅ ./benchmarks/compare/canbench_results.yml is up to date
📦 canbench_results_compare.csv available in artifacts

---------------------------------------------------

Summary:
  instructions:
    status:   No significant changes detected 👍
    counts:   [total 18 | new 0 | improved 0 | regressed 0 | unchanged 18]
    change:   [max +53.05M | p75 0 | median 0 | p25 0 | min -8.77K]
    change %: [max +0.06% | p75 0.00% | median 0.00% | p25 0.00% | min -0.00%]

  heap_increase:
    status:   No significant changes detected 👍
    counts:   [total 18 | new 0 | improved 0 | regressed 0 | unchanged 18]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  stable_memory_increase:
    status:   No significant changes detected 👍
    counts:   [total 18 | new 0 | improved 0 | regressed 0 | unchanged 18]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

---------------------------------------------------
CSV results saved to canbench_results.csv

[github-actions]

canbench 🏋 (dir: ./benchmarks/vec) e26098d 2025-06-04 15:07:45 UTC

✅ ./benchmarks/vec/canbench_results.yml is up to date
📦 canbench_results_vec.csv available in artifacts

---------------------------------------------------

Summary:
  instructions:
    status:   No significant changes detected 👍
    counts:   [total 16 | new 0 | improved 0 | regressed 0 | unchanged 16]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  heap_increase:
    status:   No significant changes detected 👍
    counts:   [total 16 | new 0 | improved 0 | regressed 0 | unchanged 16]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  stable_memory_increase:
    status:   No significant changes detected 👍
    counts:   [total 16 | new 0 | improved 0 | regressed 0 | unchanged 16]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

---------------------------------------------------
CSV results saved to canbench_results.csv

[github-actions]

canbench 🏋 (dir: ./benchmarks/btreemap) e26098d 2025-06-04 15:09:26 UTC

✅ ./benchmarks/btreemap/canbench_results.yml is up to date
📦 canbench_results_btreemap.csv available in artifacts

---------------------------------------------------

Summary:
  instructions:
    status:   No significant changes detected 👍
    counts:   [total 285 | new 0 | improved 0 | regressed 0 | unchanged 285]
    change:   [max +269.56K | p75 0 | median 0 | p25 0 | min -1.03M]
    change %: [max +0.06% | p75 0.00% | median 0.00% | p25 0.00% | min -0.17%]

  heap_increase:
    status:   No significant changes detected 👍
    counts:   [total 285 | new 0 | improved 0 | regressed 0 | unchanged 285]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  stable_memory_increase:
    status:   No significant changes detected 👍
    counts:   [total 285 | new 0 | improved 0 | regressed 0 | unchanged 285]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

---------------------------------------------------
CSV results saved to canbench_results.csv

[github-actions]

canbench 🏋 (dir: ./benchmarks/memory_manager) e26098d 2025-06-04 15:07:37 UTC

✅ ./benchmarks/memory_manager/canbench_results.yml is up to date
📦 canbench_results_memory-manager.csv available in artifacts

---------------------------------------------------

Summary:
  instructions:
    status:   No significant changes detected 👍
    counts:   [total 3 | new 0 | improved 0 | regressed 0 | unchanged 3]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  heap_increase:
    status:   No significant changes detected 👍
    counts:   [total 3 | new 0 | improved 0 | regressed 0 | unchanged 3]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  stable_memory_increase:
    status:   No significant changes detected 👍
    counts:   [total 3 | new 0 | improved 0 | regressed 0 | unchanged 3]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

---------------------------------------------------
CSV results saved to canbench_results.csv

[Copilot]

Pull Request Overview

This PR optimizes the value update mechanism in BTreeMap by introducing a dedicated method for replacing values. It refactors the code to use a new swap_value function in node.rs and an update_value helper in btreemap.rs, streamlining and unifying the update process.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/btreemap/node.rs	Added swap_value to replace a node’s value and extract the old value efficiently.
src/btreemap.rs	Replaced direct swap_entry calls with update_value to standardize value updates and persist node changes.

Comments suppressed due to low confidence (1)

src/btreemap/node.rs:159

• [nitpick] The name 'swap_value' may be misleading as it implies a bilateral swap, but it only replaces the value; consider renaming it to 'replace_value' for improved clarity.

/// Replaces the value at `idx` and returns the old one.