Re: [Haskell-beginners] How to display a time difference?

18 Mar 2009


      Am Mittwoch, 18. März 2009 11:28 schrieb Colin Paul Adams:
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"Yitzchak" == Yitzchak Gale  writes:
Yitzchak> Colin Paul Adams wrote:
    >> The code of the following routine is intended to indicate how
    >> long it takes for the computer to make a move. However the time
    >> is printed (as very close to zero) long before the move is
    >> made.
Yitzchak> You are writing a thunk to the IORef. It only gets
    Yitzchak> computed later on when you read the value.
Yitzchak> Try using:
    >> readIORef game_state_ior >>= evaluate
    >> . update_interactive_from_move move >>= writeIORef
    >> game_state_ior
Yitzchak> evaluate is in Control.Exception.
Still no joy with:
play_move :: IORef Game_state -> IO ()
play_move game_state_ior = do
  (_, state, _) <- readIORef game_state_ior
  putStr "Playing AI: "
  start_time <- getCurrentTime
  let move = recommended_move state
  readIORef game_state_ior >>=
    evaluate . update_interactive_from_move move >>=
             writeIORef game_state_ior
  end_time <- getCurrentTime
  putStrLn $ show $ (diffUTCTime end_time start_time)
You would have to completely evaluate move. Depending on what type move is, 
that might require much more than what seq or evaluate do.

Perhaps

import Control.Parallel.Strategies

let move = ...
(rnf move) `seq` mofifyIORef (...)

?

Re: [Haskell-beginners] How to display a time difference?

Daniel Fischer