choice_vs_result.fs

open BenchmarkDotNet.Attributes
open BenchmarkDotNet.Running
open System
open ExtCore.Control

[<MemoryDiagnoser>]
type Test() =
    let choiceFun x y = x |> Choice.bind (fun _ -> y)
    let resultFun x y = x |> Result.bind (fun _ -> y)

    [<Benchmark(Baseline = true)>]
    member __.Choice() : unit =
        choice {
            let! x = choiceFun (Choice1Of2 0) (Choice1Of2 0)
            let! y = choiceFun (Choice1Of2 1) (Choice1Of2 1)
            let! z = choiceFun (Choice1Of2 2) (Choice1Of2 2)
            let! h = choiceFun (Choice1Of2 3) (Choice1Of2 3)
            return! Choice1Of2 (x + y + z + h)
        } |> ignore


    [<Benchmark>]
    member __.Result() : unit =
        result {
            let! x = resultFun (Ok 0) (Ok 0)
            let! y = resultFun (Ok 1) (Ok 1)
            let! z = resultFun (Ok 2) (Ok 2)
            let! h = resultFun (Ok 3) (Ok 3)
            return! Ok (x + y + z + h)
        } |> ignore

[<EntryPoint>]
let main _ =
    printfn "%O" (BenchmarkRunner.Run<Test>())
    Console.ReadKey() |> ignore
    0

## Windows

BenchmarkDotNet=v0.10.9, OS=Windows 10 Redstone 2 (10.0.15063)
Processor=Intel Core i7-4790K CPU 4.00GHz (Haswell), ProcessorCount=8
Frequency=3906254 Hz, Resolution=255.9997 ns, Timer=TSC
.NET Core SDK=2.0.0
  [Host]     : .NET Core 2.0.0 (Framework 4.6.00001.0), 64bit RyuJIT DEBUG
  DefaultJob : .NET Core 2.0.0 (Framework 4.6.00001.0), 64bit RyuJIT


 Method |        Mean |     Error |    StdDev | Scaled | ScaledSD |  Gen 0 | Allocated |
------- |------------:|----------:|----------:|-------:|---------:|-------:|----------:|
 Choice |    67.18 ns | 0.0947 ns | 0.0840 ns |   1.00 |     0.00 | 0.0743 |     312 B |
 Result | 1,039.70 ns | 0.8317 ns | 0.6494 ns |  15.48 |     0.02 | 0.0286 |     128 B |
 
 ## Ubuntu
 
 BenchmarkDotNet=v0.10.9, OS=ubuntu 17.04
Processor=Intel Core i7-4790K CPU 4.00GHz (Haswell), ProcessorCount=8
.NET Core SDK=2.0.0
  [Host]     : .NET Core 2.0.0 (Framework 4.6.00001.0), 64bit RyuJIT DEBUG
  DefaultJob : .NET Core 2.0.0 (Framework 4.6.00001.0), 64bit RyuJIT


 Method |     Mean |     Error |    StdDev | Scaled |  Gen 0 | Allocated |
------- |---------:|----------:|----------:|-------:|-------:|----------:|
 Choice | 102.6 ns | 0.0679 ns | 0.0567 ns |   1.00 | 0.0743 |     312 B |
 Result | 148.7 ns | 0.2098 ns | 0.1859 ns |   1.45 | 0.0303 |     128 B |