Add Java implementation of the h2 histogram#1
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A pure-Java port of the iopsystems h2 histogram, producing byte-for-byte identical bucketing to the Rust histogram crate. Mirrors the code organization of the Go and Python implementations: - Config: bucketing parameters and value<->index conversions - Histogram: dense histogram with record/percentile/merge/subtract/downsample - SparseHistogram: columnar (index, count) form for storage - CumulativeHistogram: read-only cumulative form with O(log n) percentiles and a precomputed midpoint-estimated mean - Bucket / PercentileResult / BucketWithQuantiles value types Values and counts are u64 carried in Java longs with unsigned semantics, so the full u64 range is supported. The bucketing math is verified against the exact assertions from the Rust crate's own unit tests (src/config.rs). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_016Bb8BttJZHuy6zh957NMGT
This was referenced Jul 10, 2026
Single-threaded record-path benchmark at matched relative-error levels (h2 grouping powers 3/7/14 vs HDR 1/2/4 significant digits), with value streams touching from 64 buckets up to the full counter array to stress different cache levels. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_016Bb8BttJZHuy6zh957NMGT
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_016Bb8BttJZHuy6zh957NMGT
thinkingfish
marked this pull request as ready for review
July 10, 2026 14:58
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A pure-Java implementation of the iopsystems h2 histogram, using the Rust
histogramcrate as the reference and mirroring the code organization and README structure of the Go and Python ports.What's included
Config— bucketing parameters,valueToIndex/indexToLowerBound/indexToUpperBound,totalBuckets,error, plusfromTotalBucketsfor inferring the grouping power from a bare bucket count (Rezolus parquet files).Histogram— dense histogram:increment,record,recordMany,percentile(s),merge,subtract,downsample,toSparse,toCumulative,fromBuckets.SparseHistogram— columnar(index, count)form (the Rezolus:bucket_indices/:bucket_countslayout):fromHistogram,fromParts,toDense,toCumulative.CumulativeHistogram— read-only cumulative form (the crate'sCumulativeROHistogram): binary-searchpercentile(s), precomputed midpoint-estimatedmean,bucketQuantileRange,bucketsWithQuantiles.Bucket/PercentileResult/BucketWithQuantiles— value types (Java records).Design notes
u64carried in Javalongs with unsigned semantics (Long.compareUnsigned,Long.numberOfLeadingZeros,>>>), so the fullu64range is supported, exactly like the Rust crate and the Go port.0.1.0-SNAPSHOT; the README documents the release flow.Correctness
src/config.rs), the same approach used by the Go and Python ports. 36 tests, all passing.valueToIndex/ bucket bounds against the Go implementation over 40,000 random values spanning the fullu64range (grouping powers 3 and 7): zero mismatches.🤖 Generated with Claude Code
https://claude.ai/code/session_016Bb8BttJZHuy6zh957NMGT
Generated by Claude Code