Improve performance symmetry of Set.intersect

.azuredevops/dependabot.yml

@@ -1,5 +1,5 @@
-version: 2
-
-# Disabling dependabot on Azure DevOps as this is a mirrored repo. Updates should go through github.
-enable-campaigned-updates: false
-enable-security-updates: false
+version: 2
+
+# Disabling dependabot on Azure DevOps as this is a mirrored repo. Updates should go through github.
+enable-campaigned-updates: false
+enable-security-updates: false

TestFinal/Program.fs

@@ -0,0 +1,60 @@
+open System
+open Microsoft.FSharp.Collections
+
+[<CustomEquality; CustomComparison>]
+type Element = 
+    { Id: int; Version: string }
+    interface IComparable with
+        member x.CompareTo(obj) = 
+            match obj with
+            | :? Element as other -> compare x.Id other.Id
+            | _ -> -1
+    override x.Equals(obj) = 
+        match obj with
+        | :? Element as other -> x.Id = other.Id
+        | _ -> false
+    override x.GetHashCode() = hash x.Id
+
+let oldIntersect (a: Set<'T>) (b: Set<'T>) =
+    a |> Set.filter (fun item -> b.Contains item)
+
+let cleanGC () = 
+    GC.Collect()
+    GC.WaitForPendingFinalizers()
+    GC.Collect()
+
+let measure f iterations =
+    let sw = Diagnostics.Stopwatch.StartNew()
+    for _ in 1 .. iterations do ignore (f())
+    sw.Stop()
+    float sw.Elapsed.TotalMilliseconds / float iterations
+
+let run name (a: Set<Element>) (b: Set<Element>) =
+    printf "Benchmarking %-25s... " name
+    cleanGC()
+    let oldTime = measure (fun () -> oldIntersect a b) 5
+    cleanGC()
+    let newTime = measure (fun () -> Set.intersect a b) 5
+    let result = Set.intersect a b
+    let idOk = if not result.IsEmpty then (result.MinimumElement).Version = "FromA" else true
+    printfn "Done"
+    (name, oldTime, newTime, (oldTime/newTime), idOk)
+
+printfn "Generating Data..."
+let hA = Set.ofSeq (seq { for i in 1 .. 1_000_000 -> { Id = i; Version = "FromA" } })
+let hB = Set.ofSeq (seq { for i in 1 .. 1_000_000 -> { Id = i; Version = "FromB" } })
+let tB = Set.ofSeq (seq { for i in 1 .. 10 -> { Id = i; Version = "FromB" } })
+let tA = Set.ofSeq (seq { for i in 1 .. 10 -> { Id = i; Version = "FromA" } })
+
+let res = [
+    run "Huge(a) ∩ Tiny(b)" hA tB
+    run "Tiny(a) ∩ Huge(b)" tA hB
+    run "Huge(a) ∩ Huge(b)" hA hB
+]
+
+printfn "\n%-25s | %12s | %12s | %8s | %s" "Scenario" "Old (Actual)" "New (Actual)" "Speedup" "Identity OK"
+printfn "%s" (String.replicate 85 "-")
+for (n, o, nw, s, i) in res do
+    printfn "%-25s | %10.4f ms | %10.4f ms | %7.2fx | %11b" n o nw s i
+
+printfn "\nAssembly: %s" (typeof<Set<int>>.Assembly.Location)

TestFinal/TestFinal.fsproj

@@ -0,0 +1,19 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+    <DisableImplicitFSharpCoreReference>true</DisableImplicitFSharpCoreReference>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="Program.fs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Reference Include="FSharp.Core">
+      <HintPath>../artifacts/bin/FSharp.Core/Debug/netstandard2.0/FSharp.Core.dll</HintPath>
+    </Reference>
+  </ItemGroup>
+
+</Project>

docs/release-notes/.FSharp.Core/10.0.300.md

@@ -0,0 +1,3 @@
+### Fixed
+
+* Optimize Set.intersect performance symmetry and preserve identity from the first set argument. ([PR #19291](https://github.com/dotnet/fsharp/pull/19291)) (Fixes #19139)

docs/release-notes/.FSharp.Core/9.0.200.md

@@ -1,14 +1,14 @@
-### Fixed
-
-* Fix exception on Post after MailboxProcessor was disposed ([Issue #17849](https://github.com/dotnet/fsharp/issues/17849), [PR #17922](https://github.com/dotnet/fsharp/pull/17922))
-* Fix missing null annotation in Async.SwitchToContext ([Issue #18055](https://github.com/dotnet/fsharp/issues/18055), [PR #18059](https://github.com/dotnet/fsharp/pull/18059))
-
-### Added
-
-### Changed
-
-* String function changed to guarantee a non-null string return type ([PR #17809](https://github.com/dotnet/fsharp/pull/17809))
-* Add Parameters as valid target for the Struct attribute ([Language suggestion #1136](https://github.com/fsharp/fslang-suggestions/issues/1136), [PR #18098](https://github.com/dotnet/fsharp/pull/18098))
-
-
-### Breaking Changes
+### Fixed
+
+* Fix exception on Post after MailboxProcessor was disposed ([Issue #17849](https://github.com/dotnet/fsharp/issues/17849), [PR #17922](https://github.com/dotnet/fsharp/pull/17922))
+* Fix missing null annotation in Async.SwitchToContext ([Issue #18055](https://github.com/dotnet/fsharp/issues/18055), [PR #18059](https://github.com/dotnet/fsharp/pull/18059))
+
+### Added
+
+### Changed
+
+* String function changed to guarantee a non-null string return type ([PR #17809](https://github.com/dotnet/fsharp/pull/17809))
+* Add Parameters as valid target for the Struct attribute ([Language suggestion #1136](https://github.com/fsharp/fslang-suggestions/issues/1136), [PR #18098](https://github.com/dotnet/fsharp/pull/18098))
+
+
+### Breaking Changes