TheBurningMonk - Euler - 5

tbm_euler_5.fs

open System.Diagnostics

module ``TheBurningMonk - Euler`` =
    // collated from :- https://github.com/theburningmonk/ProjectEuler-FSharp-Solutions/tree/master/ProjectEulerSolutions/ProjectEulerSolutions
    // documentation :- http://theburningmonk.com/project-euler-solutions/
    open System
    open System.Numerics

    let inline private validate expected received =
        if expected <> received then
            failwith <| sprintf "Invalid answer - expected=%A received=%A" expected received

    let ``5`` () =
        let isEvenlyDivided(n, m) = n % m = 0
        let isEvenlyDividedByAll(n, numbers) = numbers |> Seq.forall (fun x -> isEvenlyDivided(n, x))
 
        let findSmallestCommonMultiple(numbers) =
            let max = Array.max(numbers)
            Seq.unfold (fun x -> Some(x, x + 1)) 1
            |> Seq.map (fun x -> x * max)
            |> Seq.filter (fun x -> isEvenlyDividedByAll(x, numbers))
            |> Seq.head
 
        let commonMultiplier = findSmallestCommonMultiple [|1..20|]

        validate 232792560 commonMultiplier

    let ``5a`` () =
        let isEvenlyDivided(n, m) = n % m = 0
        let isEvenlyDividedByAll(n, numbers) = numbers |> Seq.forall (fun x -> isEvenlyDivided(n, x))
 
        let findSmallestCommonMultiple(numbers) =
            let max = Seq.max(numbers)
            Seq.unfold (fun x -> Some(x, x + 1)) 1
            |> Seq.map (fun x -> x * max)
            |> Seq.filter (fun x -> isEvenlyDividedByAll(x, numbers))
            |> Seq.head
 
        let commonMultiplier = findSmallestCommonMultiple (Seq.ofArray [|1..20|])

        validate 232792560 commonMultiplier

    let ``5b`` () =
        let isEvenlyDivided(n, m) = n % m = 0
        let isEvenlyDividedByAll(n, numbers) = numbers |> Array.forall (fun x -> isEvenlyDivided(n, x))
 
        let findSmallestCommonMultiple(numbers) =
            let max = Array.max(numbers)
            Seq.unfold (fun x -> Some(x, x + 1)) 1
            |> Seq.map (fun x -> x * max)
            |> Seq.filter (fun x -> isEvenlyDividedByAll(x, numbers))
            |> Seq.head
 
        let commonMultiplier = findSmallestCommonMultiple [|1..20|]

        validate 232792560 commonMultiplier
 
let time what f =
    let sw = Stopwatch.StartNew ()
    let count = f 500000
    printfn "%s: %d (%d)" what sw.ElapsedMilliseconds count

let tests = [|
    "TheBurningMonk - Euler -   5 |", ``TheBurningMonk - Euler``.``5``, 2
    "TheBurningMonk - Euler -  5a |", ``TheBurningMonk - Euler``.``5a``, 2
    "TheBurningMonk - Euler -  5b |", ``TheBurningMonk - Euler``.``5b``, 2
|]

[<EntryPoint>]
let main argv =
    printfn (match sizeof<nativeint> with
             | 4 -> "32-bit"
             | 8 -> "64-bit"
             | _ -> "unknown bitage")

    printf "warming up"
    for _, f, iterations in tests do
        if iterations > 1 then
            f ()
        printf "."
    printfn "\n"

    for name, f, iterations in tests do
        let sw = Stopwatch.StartNew ()
        for i = 1 to iterations do
            f ()
        printfn "%s %d" name sw.ElapsedMilliseconds
    0