{
  "format": "kotoba.public-runtime-comparison/v2",
  "candidate": "Amu native",
  "domains": [
    {
      "id": "narrow-arithmetic",
      "label": "Narrow arithmetic",
      "exactResultVerified": true
    },
    {
      "id": "wide-register-pressure",
      "label": "Wide register pressure",
      "exactResultVerified": true
    },
    {
      "id": "deep-spill-pressure",
      "label": "Deep spill pressure",
      "exactResultVerified": true
    },
    {
      "id": "call-preservation",
      "label": "Call preservation",
      "exactResultVerified": true
    },
    {
      "id": "branch-call-control-flow",
      "label": "Branch + call control flow",
      "exactResultVerified": true
    },
    {
      "id": "loop-call-back-edge",
      "label": "Loop call back edge",
      "exactResultVerified": true
    }
  ],
  "sources": {
    "harness": "https://github.com/kotoba-lang/amu/blob/main/scripts/runtime-multidomain-suite.mjs",
    "manifest": "https://github.com/kotoba-lang/amu/blob/main/bench/runtime-comparison/multidomain-suite.json",
    "method": "https://github.com/kotoba-lang/amu/blob/main/docs/performance.md#multi-domain-qualification-floor"
  },
  "comparators": [
    {
      "id": "rust",
      "label": "Rust",
      "version": "rustc 1.98.0 (88d9e12ae 2026-08-18) (Homebrew)",
      "coverage": "6/6"
    },
    {
      "id": "clang-c11",
      "label": "Clang / C11",
      "version": "Apple clang version 17.0.0 (clang-1700.6.4.2)",
      "coverage": "6/6"
    },
    {
      "id": "zig",
      "label": "Zig",
      "version": "0.16.0",
      "coverage": "6/6"
    },
    {
      "id": "go",
      "label": "Go c-shared",
      "version": "go version go1.27.0 darwin/arm64",
      "coverage": "6/6"
    },
    {
      "id": "swift",
      "label": "Swift",
      "version": "Apple Swift version 6.2.4 (swiftlang-6.2.4.1.4 clang-1700.6.4.2)",
      "coverage": "6/6"
    }
  ],
  "host": "Apple M4, 10 logical CPUs, 16 GiB",
  "commonBoundary": "one external C runner invokes every native artifact through the same eight-i64-argument indirect-call ABI; loading and symbol resolution finish before timing",
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      "reasons": [
        "improvement-below-threshold",
        "not-separated-from-noise"
      ],
      "qualifiedRuns": 0,
      "baselineMedian": 6.41,
      "comparator": "clang-c11",
      "candidateMedian": 6.53,
      "domain": "narrow-arithmetic",
      "runs": 5
    },
    {
      "qualified": true,
      "improvement": 0.10879926203044145,
      "reasons": [],
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      "baselineMedian": 6.5,
      "comparator": "clang-c11",
      "candidateMedian": 5.8,
      "domain": "wide-register-pressure",
      "runs": 5
    },
    {
      "qualified": true,
      "improvement": 0.09260775579719598,
      "reasons": [],
      "qualifiedRuns": 5,
      "baselineMedian": 10.23,
      "comparator": "clang-c11",
      "candidateMedian": 9.23,
      "domain": "deep-spill-pressure",
      "runs": 5
    },
    {
      "qualified": false,
      "improvement": -0.003344947735192013,
      "reasons": [
        "improvement-below-threshold",
        "not-separated-from-noise"
      ],
      "qualifiedRuns": 0,
      "baselineMedian": 4.82,
      "comparator": "clang-c11",
      "candidateMedian": 4.85,
      "domain": "call-preservation",
      "runs": 5
    },
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      "improvement": -0.07052447677113449,
      "reasons": [
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      ],
      "qualifiedRuns": 0,
      "baselineMedian": 4.67,
      "comparator": "clang-c11",
      "candidateMedian": 4.98,
      "domain": "branch-call-control-flow",
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    },
    {
      "qualified": false,
      "improvement": -0.0008940148370939136,
      "reasons": [
        "improvement-below-threshold",
        "not-separated-from-noise"
      ],
      "qualifiedRuns": 0,
      "baselineMedian": 139.84,
      "comparator": "clang-c11",
      "candidateMedian": 140.59,
      "domain": "loop-call-back-edge",
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    },
    {
      "qualified": true,
      "improvement": 0.8470510676284386,
      "reasons": [],
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      "baselineMedian": 42.84,
      "comparator": "go",
      "candidateMedian": 6.53,
      "domain": "narrow-arithmetic",
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    },
    {
      "qualified": true,
      "improvement": 0.8596539367918132,
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      "baselineMedian": 41.07,
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    },
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      "baselineMedian": 51.86,
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    },
    {
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      "baselineMedian": 32.49,
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    },
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      "baselineMedian": 33.84,
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    },
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      "reasons": [
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      "baselineMedian": 141.73,
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      "domain": "loop-call-back-edge",
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    {
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      "domain": "branch-call-control-flow",
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    {
      "qualified": true,
      "improvement": 0.24817326721665062,
      "reasons": [],
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      "baselineMedian": 186.09,
      "comparator": "swift",
      "candidateMedian": 140.59,
      "domain": "loop-call-back-edge",
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    {
      "qualified": true,
      "improvement": 0.20118699927654676,
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      "baselineMedian": 8.24,
      "comparator": "zig",
      "candidateMedian": 6.53,
      "domain": "narrow-arithmetic",
      "runs": 5
    },
    {
      "qualified": true,
      "improvement": 0.1691550607964458,
      "reasons": [],
      "qualifiedRuns": 5,
      "baselineMedian": 6.97,
      "comparator": "zig",
      "candidateMedian": 5.8,
      "domain": "wide-register-pressure",
      "runs": 5
    },
    {
      "qualified": true,
      "improvement": 0.050988250608022354,
      "reasons": [],
      "qualifiedRuns": 2,
      "baselineMedian": 9.71,
      "comparator": "zig",
      "candidateMedian": 9.23,
      "domain": "deep-spill-pressure",
      "runs": 5
    },
    {
      "qualified": true,
      "improvement": 0.4293867036559992,
      "reasons": [],
      "qualifiedRuns": 5,
      "baselineMedian": 8.44,
      "comparator": "zig",
      "candidateMedian": 4.85,
      "domain": "call-preservation",
      "runs": 5
    },
    {
      "qualified": true,
      "improvement": 0.43792354637013736,
      "reasons": [],
      "qualifiedRuns": 5,
      "baselineMedian": 8.95,
      "comparator": "zig",
      "candidateMedian": 4.98,
      "domain": "branch-call-control-flow",
      "runs": 5
    },
    {
      "qualified": true,
      "improvement": 0.3239834478875583,
      "reasons": [],
      "qualifiedRuns": 5,
      "baselineMedian": 207.01,
      "comparator": "zig",
      "candidateMedian": 140.59,
      "domain": "loop-call-back-edge",
      "runs": 5
    }
  ],
  "preparedIndexSha256": "9f254dcb434bfce22602e8dadda129bae29c11caedd17dd43c424eec3b6a4651",
  "score": {
    "qualifiedPairs": 19,
    "totalPairs": 30,
    "runs": 5,
    "scoreByRun": [
      19,
      19,
      19,
      20,
      20
    ],
    "observedRange": [
      19,
      20
    ],
    "stableQualifiedPairs": 19,
    "basis": "median of 5 host-qualified runs; 19 of the 30 pairs qualified in every run",
    "policy": "perfgate default-v1: >= 5% mean improvement AND separated from the arms' own spread"
  },
  "semanticCoverage": {
    "requiredComparatorDomainPairs": 30,
    "completeComparatorDomainPairs": 30,
    "allKnownAnswersVerified": true
  },
  "sourceReportSha256": "66b81c7403100a96c9d81a3cc7876dcf2bc69d64c42c67af937b8bf223fa493a",
  "speedQualification": {
    "verdict": "qualified-host-load",
    "fastestClaimQualified": false,
    "criterion": "busy-cpu-fraction <= 0.10 over 1s, three consecutive samples; load1 recorded as diagnostic",
    "quietGateSamples": [
      {
        "busyCpuFraction": 0.090034965034965,
        "load1": 3.484375,
        "qualified": true
      },
      {
        "busyCpuFraction": 0.068815331010453,
        "load1": 3.365234375,
        "qualified": true
      },
      {
        "busyCpuFraction": 0.07577092511013217,
        "load1": 3.365234375,
        "qualified": true
      }
    ],
    "explanation": "Host-qualified. 19 of 30 candidate/comparator/domain pairs pass perfgate (median of 5 runs, observed 19-20; 19 qualified in every run). The bounded fastest claim requires all 30 in every run. At least two of those pairs are provably unwinnable -- amu, clang and rustc compile the narrow-arithmetic kernel to the same 61-instruction sequence -- so the bounded claim is not merely unqualified, it is unattainable."
  },
  "provenUnwinnablePairs": {
    "pairs": [
      {
        "domain": "narrow-arithmetic",
        "comparator": "clang-c11"
      },
      {
        "domain": "narrow-arithmetic",
        "comparator": "rust"
      }
    ],
    "evidence": "amu, clang -O3 and rustc -O3 compile this kernel to the same 61-instruction sequence; clang and rustc are byte-identical, amu differs only in register numbers",
    "verified": "2026-09-06",
    "consequence": "the bounded fastest claim requires a >= 5% margin on every pair, which cannot exist against identical code"
  },
  "target": "Darwin arm64 native",
  "generatedAt": "2026-09-07T03:45:08.683Z",
  "metric": "steady-state nanoseconds per kernel; lower is better",
  "compilerCommit": "42f092ea5b6192f02f3c361535a37521b2ab6ab1"
}