Speed up cron next-fire-time computation with a bitmask fast path#3126
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CronExpression.GetTimeAfter located the next allowed value for each field via SortedSet<int> lookups whose slow path allocates a GetViewBetween view and walks a red-black tree - on the scheduler hot path, once per trigger fire. Add a parallel bitmask representation of the parsed fields (seconds, minutes, hours, days-of-month, months, days-of-week), built from the existing SortedSet fields after parsing, and route the hot lookups through an O(1) trailing-zero bit scan. The protected SortedSet fields and GetSet/AddToSet stay unchanged, so there is no public/protected API or serialization break; the years field stays on the set path because its range is open-ended. BitUtil provides TrailingZeroCount via System.Numerics.BitOperations on net8+ and a De Bruijn lookup-table fallback for net462/net472/netstandard2.0. Next-occurrence is now allocation-free (was up to ~23 KB per 100 chained calls) and 6-35% faster. Adds a randomized differential test and restructures the cron benchmarks (separate parse / next-occurrence, plus a head-to-head against the Cronos library). Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]> Claude-Session: https://claude.ai/code/session_01WEQMdnqSWJkTN7KDemLtre
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Port of the main-branch optimization (#3128) to 3.x. GetTimeAfter rebuilt a DateTimeOffset after every field even when the field already matched - and since each d.Year / d.Month / d.Day / ... access re-decomposes the tick count, an unchanged rebuild cost several decompositions plus a recomposition. In the common steady state most fields are already satisfied, so this was pure waste. - The second / minute / hour / day / month / year sections now skip rebuilding the date when the field did not change. The value they used to rebuild is provably identical to the existing one (same components, milliseconds already stripped at loop entry, same offset), so behavior is unchanged. - BitUtil.TrailingZeroCount / PopCount / TryGetMinValueStartingFrom are marked AggressiveInlining; the dead "start outside [0,63]" guard on the hottest method becomes a Debug.Assert (callers always pass an in-range value). Next-occurrence computation is 27-36% faster (largest on day-of-week, L and year-constrained expressions, which iterate the loop more). All 1401 unit tests pass on net10.0 and net472 (the net472 run exercises the De Bruijn fallback), including the randomized differential test added in #3126. Note: 3.x's L/W day-of-month handling is already allocation-free (it computes the day inline, with no per-month SortedSet), so the companion L/W zero-allocation change in #3128 has no 3.x counterpart. Claude-Session: https://claude.ai/code/session_01WEQMdnqSWJkTN7KDemLtre Co-authored-by: Claude Opus 4.8 (1M context) <[email protected]>
This was referenced Jun 27, 2026
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build(deps): Bump Quartz.AspNetCore from 3.18.1 to 3.18.2
eurofurence/ef-app_backend-dotnet-core#433
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Summary
Inspired by the Cronos library, which represents each cron field as an integer bitmask and finds the next matching value with a trailing-zero bit scan.
CronExpression.GetTimeAfter(run once per trigger fire on the scheduler hot path) previously located the next allowed value for each field viaSortedSet<int>lookups whose slow path allocates aGetViewBetweenview and walks a red-black tree.This PR adds a non-breaking bitmask fast path:
Quartz.Util.BitUtil—TrailingZeroCountviaSystem.Numerics.BitOperationson net8+, with a De Bruijn lookup-table fallback fornet462/net472/netstandard2.0.CronExpressionkeeps itsprotected SortedSet<int>fields andGetSet/AddToSetexactly as-is (no public/protected API or serialization break), and additionally builds[NonSerialized]bitmask fields from those sets after parsing (BuildBitmasks, called fromBuildExpression, so it also runs on deserialize and for subclasses).GetTimeAfterroutes its seconds/minutes/hours/months/days lookups through an O(1) bit scan. Theyearsfield stays on the set path (open-ended range).Results
BenchmarkDotNet, AMD Ryzen 9 5950X, .NET 10, ShortRun. Next-occurrence (GetNextValidTimeAfter):0 0/5 * * * ?(×100)0/15 * * * * ?(×100)0 0,10,…,50 * * * ?(×100)The hot path is now allocation-free; expressions with ranges/steps/lists (which hit the old
GetViewBetweenslow path) see the largest gains. Parsing is intentionally unchanged on this branch (the layered approach keeps the sets); the bitmask-parse win is on the 4.x PR.External yardstick (
CronComparisonBenchmarkvs Cronos 0.13.0, equivalent 6-field expressions): QuartzGetNextis now zero-allocation like Cronos; absolute time is still ~8–20× Cronos because the loop constructs manyDateTimeOffsetvalues per iteration (a deeper rewrite, out of scope here).Validation
CronExpressionTest,CronExpressionHashTest,CronTriggerTest,CronScheduleBuilderTest— 296 cron cases; full unit suite 1384 green.CronExpressionDifferentialTest— seeded-random expressions vs an independent brute-force oracle, plus aBitUtilfuzz test, run on both TFMs.The companion 4.x change is #3127 (puts the bitmask inside
CronField, also speeding parse).🤖 Generated with Claude Code
https://claude.ai/code/session_01WEQMdnqSWJkTN7KDemLtre