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perf: reduce allocations in NewV3 and NewV5#221

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anatoly-kussul:perf-v3-v5-allocations
Sep 25, 2025
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perf: reduce allocations in NewV3 and NewV5#221
cameracker merged 2 commits into
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anatoly-kussul:perf-v3-v5-allocations

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@anatoly-kussul

@anatoly-kussul anatoly-kussul commented Jul 9, 2025

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goos: linux
goarch: amd64
pkg: github.com/gofrs/uuid/v5
cpu: 12th Gen Intel(R) Core(TM) i5-12400F
                   │     old     │                 new                 │
                   │   sec/op    │   sec/op     vs base                │
Generator/NewV3-12   169.5n ± 1%   102.5n ± 1%  -39.55% (p=0.000 n=10)
Generator/NewV5-12   183.2n ± 2%   113.6n ± 1%  -37.96% (p=0.000 n=10)

                   │    old     │                  new                  │
                   │    B/op    │   B/op    vs base                     │
Generator/NewV3-12   144.0 ± 0%   0.0 ± 0%  -100.00% (p=0.000 n=10)
Generator/NewV5-12   168.0 ± 0%   0.0 ± 0%  -100.00% (p=0.000 n=10)

                   │    old     │                   new                   │
                   │ allocs/op  │ allocs/op   vs base                     │
Generator/NewV3-12   4.000 ± 0%   0.000 ± 0%  -100.00% (p=0.000 n=10)
Generator/NewV5-12   4.000 ± 0%   0.000 ± 0%  -100.00% (p=0.000 n=10)

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cameracker requested a review from Copilot September 25, 2025 01:11
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Pull Request Overview

This PR optimizes the allocation performance of UUID generation methods NewV3 and NewV5 by eliminating all heap allocations. The changes inline the hash computation logic and use a pre-allocated buffer to avoid unnecessary memory allocations.

  • Removes the generic newFromHash helper function and inlines hash computation directly in NewV3 and NewV5
  • Pre-allocates hash result buffer with make([]byte, 0, capacity) to avoid allocations in h.Sum(nil)
  • Uses named return values to leverage zero-value initialization

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codecov Bot commented Sep 25, 2025 •
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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (f37c04d) to head (7da2e32).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files 
@@            Coverage Diff            @@
##            master      #221   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            5         5           
  Lines          516       517    +1     
=========================================
+ Hits           516       517    +1

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cameracker requested a review from Copilot September 25, 2025 01:13
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Pull Request Overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

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@cameracker
cameracker merged commit e1fb84e into gofrs:master Sep 25, 2025
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cameracker commented Sep 25, 2025

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@anatoly-kussul thank you very much for this contribution, and apologies it took me a while to get to it. Nice change! Simple but impactful perf improvements are appreciated.

@coderabbitai coderabbitai Bot mentioned this pull request Mar 20, 2026
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