gistfile1.fs

open System
open System.Text
open System.Diagnostics

let main () =

    let sample = @"
        Lorem ipsum dolor sit amet, consectetur adipiscing elit. 
        Ut eget ligula justo, et malesuada diam. Phasellus lobortis 
        risus a lorem lacinia pulvinar varius nulla molestie. Nullam 
        et sapien nec leo elementum convallis. Pellentesque habitant 
        morbi tristique senectus et netus et malesuada fames ac turpis 
        egestas.
        Lorem ipsum dolor sit amet, consectetur adipiscing elit. 
        Ut eget ligula justo, et malesuada diam. Phasellus lobortis 
        risus a lorem lacinia pulvinar varius nulla molestie. Nullam 
        et sapien nec leo elementum convallis. Pellentesque habitant 
        morbi tristique senectus et netus et malesuada fames ac turpis 
        egestas.
        Lorem ipsum dolor sit amet, consectetur adipiscing elit. 
        Ut eget ligula justo, et malesuada diam. Phasellus lobortis 
        risus a lorem lacinia pulvinar varius nulla molestie. Nullam 
        et sapien nec leo elementum convallis. Pellentesque habitant 
        morbi tristique senectus et netus et malesuada fames ac turpis 
        egestas.
        Lorem ipsum dolor sit amet, consectetur adipiscing elit. 
        Ut eget ligula justo, et malesuada diam. Phasellus lobortis 
        risus a lorem lacinia pulvinar varius nulla molestie. Nullam 
        et sapien nec leo elementum convallis. Pellentesque habitant 
        morbi tristique senectus et netus et malesuada fames ac turpis 
        egestas.
        Lorem ipsum dolor sit amet, consectetur adipiscing elit. 
        Ut eget ligula justo, et malesuada diam. Phasellus lobortis 
        risus a lorem lacinia pulvinar varius nulla molestie. Nullam 
        et sapien nec leo elementum convallis. Pellentesque habitant 
        morbi tristique senectus et netus et malesuada fames ac turpis 
        egestas.
        Lorem ipsum dolor sit amet, consectetur adipiscing elit. 
        Ut eget ligula justo, et malesuada diam. Phasellus lobortis 
        risus a lorem lacinia pulvinar varius nulla molestie. Nullam 
        et sapien nec leo elementum convallis. Pellentesque habitant 
        morbi tristique senectus et netus et malesuada fames ac turpis 
        egestas."

    let time iterations work =
        work () // warm up, JIT, etc.
        let sw = new Stopwatch()
        sw.Start()
        for i in 1..iterations do
            work ()
        sw.Elapsed
    
    let put (sb : StringBuilder) (buffer : char[]) index ch =
        let len = buffer.Length
        let index = if index = len then
                        sb.Append(buffer, 0, len) |> ignore; 0
                    else 
                        index
        buffer.[index] <- ch
        index + 1

    let time = time 1000

    let bufferingStringBuilder (size : int) =
        let sb = new StringBuilder()
        let buffer = System.Array.CreateInstance(typedefof<char>, size) :?> char[]
        let index = ref 0
        ((fun ch -> index := put sb buffer !index ch), 
         (fun () -> sb.Append(buffer, 0, !index).ToString()))

    let buildString (str : string) (sb : StringBuilder) (size : int) =
        let buffer = System.Array.CreateInstance(typedefof<char>, size) :?> char[]
        let rec buildString2 si di =
            if si < str.Length then
                let ch = str.[si]
                let di = if di = buffer.Length then
                             sb.Append(buffer, 0, di) |> ignore; 0
                         else 
                             di
                buffer.[di] <- ch
                buildString2 (si + 1) (di + 1)
            else
                sb.Append(buffer, 0, di)
        buildString2 0 0

    let unbufferedTest () = 
        let sb = new StringBuilder()
        for i in 1..(sample.Length - 1) do
            sb.Append(sample.[i]) |> ignore
        sb.ToString() |> ignore

    let bufferedTest () = 
        let put, flush = bufferingStringBuilder 8192
        for i in 1..(sample.Length - 1) do
            put(sample.[i])
        flush() |> ignore

    let recursiveBufferedTest () = 
        let sb = buildString sample (new StringBuilder()) 8192
        sb.ToString() |> ignore
        
    let percent (x : TimeSpan) (y : TimeSpan) = 
        ((x.TotalMilliseconds / y.TotalMilliseconds).ToString("P1"))

    for i in 1..10 do
        let unbufferedTiming        = time unbufferedTest
        let bufferedTiming          = time bufferedTest
        let recursiveBufferedTiming = time recursiveBufferedTest
        printfn "Unbuffered:Buffered = %8s | Unbuffered:Recursive %8s | Buffered:Recursive %8s" 
            (percent unbufferedTiming bufferedTiming)
            (percent unbufferedTiming recursiveBufferedTiming)
            (percent bufferedTiming recursiveBufferedTiming)

main ()

gistfile2.txt

Unbuffered:Buffered =  141.2 % | Unbuffered:Recursive  362.4 % | Buffered:Recursive  256.5 %
Unbuffered:Buffered =  138.4 % | Unbuffered:Recursive  333.6 % | Buffered:Recursive  241.1 %
Unbuffered:Buffered =  134.6 % | Unbuffered:Recursive  314.0 % | Buffered:Recursive  233.3 %
Unbuffered:Buffered =  138.0 % | Unbuffered:Recursive  404.2 % | Buffered:Recursive  293.0 %
Unbuffered:Buffered =  137.3 % | Unbuffered:Recursive  307.7 % | Buffered:Recursive  224.1 %
Unbuffered:Buffered =  138.5 % | Unbuffered:Recursive  337.7 % | Buffered:Recursive  243.9 %
Unbuffered:Buffered =  138.2 % | Unbuffered:Recursive  373.1 % | Buffered:Recursive  269.9 %
Unbuffered:Buffered =  138.8 % | Unbuffered:Recursive  338.8 % | Buffered:Recursive  244.1 %
Unbuffered:Buffered =  138.5 % | Unbuffered:Recursive  339.5 % | Buffered:Recursive  245.1 %
Unbuffered:Buffered =  137.5 % | Unbuffered:Recursive  333.1 % | Buffered:Recursive  242.3 %