hammer_a_map.fs

let cli = new System.Net.WebClient ()
let data =
    cli.DownloadString "https://raw.githubusercontent.com/dwyl/english-words/master/words.txt"
    |> fun s -> s.Split ([|"\n"; "\r"; System.Environment.NewLine|], System.StringSplitOptions.None)

printfn "found %d words - shuffling" data.Length

let r = System.Random ()
for i = 0 to data.Length-1 do
    let j = r.Next (i, data.Length-1)
    let t = data.[j]
    data.[j] <- data.[i]
    data.[i] <- t

printfn "shuffled."

let rec buildMap m n =
    if n = data.Length then m
    else
        let item = data.[n]
        buildMap (m |> Map.add item item.Length) (n+1)

for i = 1 to 3 do
    System.GC.Collect ()
    let sw = System.Diagnostics.Stopwatch.StartNew ()
    let wordMap = buildMap Map.empty 0
    let wordCount = wordMap.Count
    printfn "build: %d (%d)" sw.ElapsedMilliseconds wordCount

let rec countLength words n totalLength =
    if n = data.Length then totalLength
    else
        let length =
            words
            |> Map.find data.[n]
        countLength words (n+1) (totalLength+length)

let wordMap = buildMap Map.empty 0
for i = 1 to 3 do
    System.GC.Collect ()
    let sw = System.Diagnostics.Stopwatch.StartNew ()
    let totalLength = countLength wordMap 0 0
    printfn "lookup: %d (%d)" sw.ElapsedMilliseconds totalLength