问题
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 function.
回答1:
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?
回答2:
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.
回答3:
:set +s is really neat if use ghci, otherwise you can use Criterion.Measurement, see my answer to another question with example.
回答4:
I'm not sure how accurate it is, but using :set +s in ghci will show the time and space used for subsequent computations.
来源：https://stackoverflow.com/questions/5968614/how-to-get-a-programs-running-time-in-haskell