[Haskell-cafe] how to read CPU time vs wall time report from GHC?

[Wishnu Prasetya]

Hello Edward,

I'm using Windows 7 on Intel i7 (4 cores with hyperthreading)...

--Wish.

> Hello Wishnu,
>
> That is slightly odd. What CPU and operating system are you running on?
> Include Kernel versions if Linux.
>
> Cheers,
> Edward
>
> 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
>> option:
>>
>>     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?
>>
>> --Wish.
>>