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LAST BUILD ON BRANCH robjs-parallel-diff
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coverage: 88.737% (-0.04%) from 88.775%
40724303173

Pull #1120

github

robshakir 
ygot: Add ParallelDiff and ParallelDiffWithAtomic for lockstep diffing.

`ygot.Diff` and `ygot.DiffWithAtomic` call `findSetLeaves` on `original` and
`modified` independently through `util.Walk`. That approach clones gNMI paths,
formats `PathToString` keys for every node in both trees, and builds four
full-tree leaf maps before comparing values.

This change adds `ygot.ParallelDiff` and `ygot.ParallelDiffWithAtomic`, which
traverse `original` and `modified` in lockstep using a single mutable path
stack:

- **Type-cached descriptors**: Cache per-`reflect.Type` field classifications
  and pre-parsed `*gnmipb.PathElem` slices in `diffStructDescCache`.
- **Direct leaf comparison**: Compare pointer scalars, enums, value leaves, and
  slices directly via `reflect.Value` without boxing unchanged values.
- **Subtree fast paths**: Skip nil or pointer-identical child containers, maps,
  and map entries in `O(1)` time with zero heap allocations.
- **Lazy list keys**: Call `ΛListKeyMap()` and `keyMapAsStrings` on ancestor
  list entries only when a descendant leaf differs.

Local `-c opt` benchmarks on `exampleoc.Device` and full OpenConfig `Device`
trees show the following improvements over `ygot.Diff`:

- **`exampleoc.Device` microbenchmark**: Latency drops from `2.23 ms` to
  `17.2 µs` (`129.6x`), heap drops from `800 KB` to `4.08 KB` (`196.2x`), and
  allocations drop from `17,740` to `69` (`257.1x`).
- **Large OpenConfig `Device` (`~85K` leaves, small delta)**: Latency drops from
  `1,258.14 ms` to `9.57 ms` (`131.4x`), heap drops from `243.57 MB` to
  `0.31 MB` (`789.4x`), and allocations drop from `3.75M` to `10,935`
  (`343.0x`).

A benchmark test can follow in a separate change if needed.
Pull Request #1120: ygot: Add ParallelDiff and ParallelDiffWithAtomic for lockstep diffing.

611 of 693 new or added lines in 1 file covered. (88.17%)

2 existing lines in 1 file now uncovered.

14757 of 16630 relevant lines covered (88.74%)

1473.75 hits per line

Relevant lines Covered
16630 RELEVANT LINES 14757 COVERED LINES
1473.75 HITS PER LINE
Source Files on robjs-parallel-diff

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Builds Branch Commit Type Ran Committer Via Coverage
40724303173 robjs-parallel-diff ygot: Add ParallelDiff and ParallelDiffWithAtomic for lockstep diffing. `ygot.Diff` and `ygot.DiffWithAtomic` call `findSetLeaves` on `original` and `modified` independently through `util.Walk`. That approach clones gNMI paths, formats `PathToStr... Pull #1120 robshakir github
88.74
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