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CultMath: the oracle test names its one tolerance (power and logarithm, one ulp for another OS's libm)

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Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
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Meta Vens 2026-10-12 06:20:31 +02:00
commit abe98fc40a
1 changed files with 10 additions and 5 deletions
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15
packages/cultmath/tests/CultMath.Tests/CyclesOracleTests.cs
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@ -8,15 +8,20 @@ namespace CultMath.Tests;
/// math.cycles_* against the results of Blender 5.2.2's own Cycles on the CPU. The fixtures under
/// fixtures/cycles-oracle are written by tools/cycles-oracle/oracle.py (never by hand): each case is the
/// operands and the node's baked results as float32 bit patterns. Every function is compared at every case
/// within the tolerance its family states below; a function not named in <see cref="Tolerances"/> is held to
/// 0 ulp. Signed zeros are not distinguished (-0 equals 0), and NaN equals NaN. The fixtures come from Cycles'
/// within the tolerance named in <see cref="Tolerances"/>; a function not named there is held to 0 ulp. Signed zeros are not distinguished (-0 equals 0), and NaN equals NaN. The fixtures come from Cycles'
/// SSE4.2 CPU kernel, which does not fuse multiply-adds as C# does not (oracle.py checks this before it bakes).
/// </summary>
public sealed class CyclesOracleTests
{
// The ulp distance each function is allowed from Cycles, with the measured worst case that earned it.
// Anything absent is 0 ulp.
private static readonly Dictionary<string, (int Ulp, string Measured)> Tolerances = new();
// The ulp distance a function is allowed from Cycles. The two that call the platform's libm have the bound the
// golden fixture gives a platform libm family (GlslMirrorTests, Platform.Ulp): Blender's powf and logf are
// glibc's, measured here at 0 ulp from MathF.Pow and MathF.Log on Linux, and another OS's libm may differ by
// one. That allowance is the golden fixture's, not a measurement on another OS.
private static readonly Dictionary<string, (int Ulp, string Measured)> Tolerances = new()
{
["cycles_power"] = (1, "0 ulp on Linux"),
["cycles_logarithm"] = (1, "0 ulp on Linux"),
};
private static string FixturePath(string family) =>
Path.Combine(HlslSourceCompatibilityTests.FindCultMathRoot(), "tests", "CultMath.Tests", "fixtures", "cycles-oracle", family + ".json");