[Haskell-cafe] how to read CPU time vs wall time report from GHC?
s.w.b.prasetya at uu.nl
Sun Aug 14 20:27:47 CEST 2011
I'm using Windows 7 on Intel i7 (4 cores with hyperthreading)...
> Hello Wishnu,
> That is slightly odd. What CPU and operating system are you running on?
> Include Kernel versions if Linux.
> Excerpts from Wishnu Prasetya's message of Sun Aug 14 14:11:36 -0400 2011:
>> Hi guys,
>> I'm new in parallel programming with Haskell. I made a simple test
>> program using that par combinator etc, and was a bit unhappy that it
>> turns out to be slower than its sequential version. But firstly, I dont
>> fully understand how to read the runtime report produced by GHC with -s
>> SPARKS: 5 (5 converted, 0 pruned)
>> INIT time 0.02s ( 0.01s elapsed)
>> MUT time 3.46s ( 0.89s elapsed)
>> GC time 5.49s ( 1.46s elapsed)
>> EXIT time 0.00s ( 0.00s elapsed)
>> Total time 8.97s ( 2.36s elapsed)
>> As I understand it from the documentation, the left time-column is the
>> CPU time, whereas the right one is elapses wall time. But how come that
>> the wall time is less than the CPU time? Isn't wall time = user's
>> perspective of time; so that is CPU time + IO + etc?
>> Any help?
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