在运行一些执行并行计算的代码时,输出变得混乱:不同的消息混淆了。这是一个示例:
Iteration 1
Iteration
Iteration 23 of 19 - Calculating P&L for test window ending at 10/28/1968 12:00:00 AM
of
Iteration 4
Iteration of
Iteration 5
Iteration
Iteration 19 - Calculating P&L for test window ending at of 19 - Calculating P&L for test window ending at 5/29/1974 12:00:00 AM
6 of 878/18/1971 12:00:00 AM19 - Calculating P&L for test window ending at 3/4/1977 12:00:00 AM
of 19 of
of 19 - Calculating P&L for test window ending at 6/25/1985 12:00:00 AM
当顺序运行相同的程序时,控制台输出很好,没有乱码。
通过此功能打印到控制台:
let windowTrainTest (comm: Communication) critFoo count (model: IModel) (assets: Assets) (paramList: Parameters list) =
// Deleted some code here
if comm = Verbose then
let msg1 = sprintf "\nwindowTrainTestPandL: First date: %A, Last date: %A\nBest Criterion: %.2f\n" fDate lDate bestCriterion
let msg2 = sprintf "Best Parameters: %A\n" bestParameters
printfn "%s" <| msg1 + msg2
(pandl, wgts), bestParameters, ( ["Criterion", bestCriterion] |> Map.ofList,
["FirstDate", fDate; "LastDate", lDate] |> Map.ofList )
并行化是由程序的这一部分完成的:
let pSeqMapi f (xs: seq<'T>) = xs |> PSeq.mapi f
let trainTest n i (trainSize, fullSize) =
let takenAssets = assets |> Assets.take (min fullSize len)
lastDate takenAssets
|> printfn "\nIteration %d of %d - Calculating P&L for test window ending at %A\n" (i + 1) n
paramList
|> windowTrainTest comm' critFoo trainSize model takenAssets
let mapTrainTest (initSizes: (int * int) list) =
let f = trainTest initSizes.Length
match calcType with
| PSeq -> initSizes |> pSeqMapi f |> List.ofSeq
| _ -> initSizes |> Seq.mapi f |> List.ofSeq
有没有办法避免这种行为,例如将消息刷新到控制台?
答案 0 :(得分:6)
并行计算在不同的线程上运行,如果一个线程在printfn
中间被中断而第二个线程在第一个线程再次运行之前运行printfn
,那么它们的输出将是交织。
处理此问题的最简单方法是创建一个新函数,该函数将在lock
个调用周围使用printfn
关键字:
let lockObj = new obj()
let lockedPrintfn msg = lock lockObj (fun _ -> printfn msg)
然后用printfn
替换所有lockedPrintfn
来电,您应该得到您期望的序列化输出。你的性能会受到一点点影响,因为你的线程偶尔会花一些时间等待printfn锁定,但只要你的计算花费的时间比打印输出花费的时间长得多,你就不应该注意到性能略慢一些。
答案 1 :(得分:1)
我认为我找到了解决方案,并且它不需要锁定。我替换了行
lastDate takenAssets
|> printfn "\nIteration %d of %d - Calculating P&L for test window ending at %A\n" (i + 1) n
带
let msg = sprintf "\nIteration %d of %d - Calculating P&L for test window ending at %A\n" (i + 1) n (lastDate takenAssets)
printfn "%s" msg
我向那些知识渊博的人提供解释。