How to get a program's running time in Haskell

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臣服心动
臣服心动 2021-02-04 12:10

How can I go about getting a program\'s running time through system time functions in Haskell? I would like to measure the execution time of a whole program and/or an individual

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  • 2021-02-04 12:39

    I'm not sure how accurate it is, but using :set +s in ghci will show the time and space used for subsequent computations.

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  • 2021-02-04 12:49

    :set +s is really neat if use ghci, otherwise you can use Criterion.Measurement, see my answer to another question with example.

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  • 2021-02-04 12:52

    1) If you want to benchmark something, use the criterion package.

    2) If you want to time a function and are positive you have controlled for laziness as needed, then just use Data.Time.getCurrentTime from the time package.:

    import Data.Time
    ...
       start <- getCurrentTime
       runOperation
       stop <- getCurrentTime
       print $ diffUTCTime stop start
    

    A slicker packaging of the above pattern can be found in the timeit package.

    3) If you actually want the running time of a program that just happens to be written in Haskell then use your systems time utility. For most POSIX systems (Mac, Linux) just run:

    $ time ./SomeProgram
    

    And it will report user, wall, and system time.

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  • 2021-02-04 13:06

    Assuming you don't just want to measure the total running time of your program, like so:

     $ time ./A
    

    Then you can time a computation a number of ways in Haskell:

    • Basic timing (e.g. as in the timeit package)
    • Timing in cycles

    For more statistically sound measurement, consider

    • The Criterion package.

    Finally, in all cases, you need to think about lazy evaluation: do you want to measure the cost of fully evaluating whatever data you produce, or just to its outermost constructor?

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