Hi Michael,
I think you’re going to want a zippered iteration:
forall (part, i) in zip(field.p, field.D) { … }
-Ben
On 8/20/14, 7:38 AM, "Michael Dietrich"
<[email protected]> wrote:
>Hello,
>
>yes, you're right, I continued using the C-syntax. Now it looks much
>better.
>
>One question about this to make it perfect: If i write...
>
>forall part in field.p {
> part.f.x = 0.0;
> part.f.y = 0.0;
> part.f.z = 0.0;
>}
>
>...how can I get the index of "part" within the array "p"?
>
>bye
>
>
>Zitat von Ben Harshbarger <[email protected]>:
>
>> Hi Michael,
>>
>> Looking through your code I saw that you were passing classes as
>>arguments
>> with the ‘ref’ intent. Chapel classes are passed as references by
>>default,
>> so I don’t think you need the ref intent in most of those functions:
>>
>> // this should be fine
>> proc calc_force(parts : ParticleField) { … }
>>
>> Something else you can do to improve your code’s performance and
>> readability is to iterate directly over an array instead of its
>>underlying
>> domain:
>>
>> forall part in field.p {
>> part.f.x = 0.0;
>> part.f.y = 0.0;
>> part.f.z = 0.0;
>> }
>>
>> // instead of
>>
>> forall i in 0..field.num_parts-1 {
>> field.p[i].f.x = 0.0;
>> field.p[i].f.y = 0.0;
>> field.p[i].f.z = 0.0;
>> }
>>
>>
>>
>> Let me know if you have any additional questions.
>>
>> -Ben
>>
>>
>> On 8/18/14, 11:18 AM, "Michael Dietrich"
>> <[email protected]> wrote:
>>
>>> Hello,
>>>
>>> okay, if you want to you can read through the code [1]. :)
>>> For comparation it includes the program in C which I successfully
>>> parallelized with MPI and the same program in Chapel.
>>> I hope I didn't forget to comment important lines. If anything is
>>> unclear just ask me.
>>>
>>> Please consider the code won't win a beauty contest (especially the
>>> one in C) but at least my Chapel code is more readable than the code
>>> in C mostly written by the responsible employee. ;)
>>>
>>> bye
>>>
>>> [1] http://www-user.tu-chemnitz.de/~michd/fish.tar.gz
>>>
>>>
>>> Zitat von Lydia Duncan <[email protected]>:
>>>
>>>> Hi Michael,
>>>>
>>>> I think it will be difficult for us to offer further suggestions
>>>> without looking at the code ourselves, would you be comfortable
>>>> sending it?
>>>>
>>>> Lydia
>>>>
>>>> On 08/18/2014 05:27 AM, Michael Dietrich wrote:
>>>>> Hello,
>>>>>
>>>>> today I compiled my program with the --fast flag.
>>>>> Though it made both the serial execution much faster than before, the
>>>>> parallel one became even slower compared with the serial. I'm still
>>>>> trying to find any possible mistakes within my code but I can't find
>>>>> any. Any suggestions?
>>>>>
>>>>> bye
>>>>>
>>>>>
>>>>>
>>>>> Zitat von Tom MacDonald <[email protected]>:
>>>>>
>>>>>> Hi Michael,
>>>>>>
>>>>>> Without --fast the compiler generates runtime checks, which slows
>>>>>> down execution time.
>>>>>>
>>>>>> Please compile with the --fast flag and see how much execution
>>>>>> time improvement there is.
>>>>>>
>>>>>> Thanks
>>>>>>
>>>>>> Tom MacDonald
>>>>>>
>>>>>> On Fri, 15 Aug 2014, Tom MacDonald wrote:
>>>>>>
>>>>>>> Hi Michael,
>>>>>>>
>>>>>>> Thank you for your interest in Chapel! It's good to hear you are
>>>>>>> studying high performance programming languages.
>>>>>>>
>>>>>>> Are you compiling your Chapel program with the --fast option?
>>>>>>>
>>>>>>> We need to know that before looking deeper.
>>>>>>>
>>>>>>> Thanks
>>>>>>>
>>>>>>> Tom MacDonald
>>>>>>>
>>>>>>> On Fri, 15 Aug 2014, Michael Dietrich wrote:
>>>>>>>
>>>>>>>> Hello,
>>>>>>>>
>>>>>>>> I'm working with Chapel due to my bachelor thesis about high
>>>>>>>> performance programming languages. My current task is to
>>>>>>>>implement a
>>>>>>>> particle simulation program of which I already have the code in C.
>>>>>>>> It
>>>>>>>> includes two possible algorithms for calculating the force acting
>>>>>>>> onto
>>>>>>>> the particles: A simple but ineffective one and the
>>>>>>>> Barnes-Hut-Algorithm [1] which is much faster but a bit more
>>>>>>>> complicated. The other calculations aren't that complex so for me
>>>>>>>> only
>>>>>>>> the calculation of force is important.
>>>>>>>>
>>>>>>>> I implemented the simple algorithm at first. For comparing the
>>>>>>>> serial
>>>>>>>> and parallel execution time I surrounded everything with a
>>>>>>>> serial-statement, evaluating a bool variable I have to set in the
>>>>>>>> command line. I didn't implement the multi locale improvement yet
>>>>>>>>so
>>>>>>>> it runs only on a dual core PC, using forall-loops. Finally the
>>>>>>>> parallel one only needed half of the time of the serial, yay.
>>>>>>>>
>>>>>>>> I continued with Barnes-Hut. This one was a bit more work because
>>>>>>>> the
>>>>>>>> maintenance of the tree-structure leaves a lot of opportunities
>>>>>>>>for
>>>>>>>> mistakes. After a bit more time it was working as well.
>>>>>>>> My issue is about the parallel execution time of this algorithm.
>>>>>>>> Like
>>>>>>>> in the other one I replaced the crucial for-loop with a
>>>>>>>>forall-loop
>>>>>>>> (the serial-statement surrounds the whole program). The problem
>>>>>>>>is,
>>>>>>>> that the parallel execution time is similar to the serial one,
>>>>>>>> sometimes even longer.
>>>>>>>> Of course I don't want you to read through all my code, but could
>>>>>>>> you
>>>>>>>> tell me some possible reasons, why this effect may occur?
>>>>>>>>
>>>>>>>> thank you very much
>>>>>>>> bye
>>>>>>>> Michael
>>>>>>>>
>>>>>>>>
>>>>>>>> [1] http://beltoforion.de/barnes_hut/barnes_hut_en.html
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>-------------------------------------------------------------------
>>>>>>>>--
>>>>>>>> ---------
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>>>>>>>> Chapel-users mailing list
>>>>>>>> [email protected]
>>>>>>>> https://lists.sourceforge.net/lists/listinfo/chapel-users
>>>>>>>>
>>>>>>>
>>>>>>>
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>>>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
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>>>
>>>
>>>
>>>
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