That definitely helps, thank you !
On Mon, Aug 29, 2016 at 2:41 PM, Brad Chamberlain <[email protected]> wrote:
>
> PS -- The "typically" is because the author of a domain map can implement
> the parallelism in the forall loop any way they want to. The standard
> distributions that we supply are intended to target both inter- and
> intra-locale parallelism.
>
>
> On Mon, 29 Aug 2016, Brad Chamberlain wrote:
>
>
>> Hi Hui --
>>
>> Forall loops overdistributed domains/arrays typically enable parallelism
>> both across locales and within a compute node. So the better sketch of how
>> it would be rewritten
>>
>> coforall loc in Locales {
>> on loc {
>> forall msg in local_MessageSpace {
>> writeln();
>> }
>> }
>> }
>>
>> Where that inner 'forall' would use multicore parallelism within the
>> locale, much as a forall loop over a default domain/array would.
>>
>> Hope this helps,
>> -Brad
>>
>>
>> On Fri, 26 Aug 2016, Hui Zhang wrote:
>>
>> Hello,
>>>
>>> I have a question about forall, considering the simple example of
>>> hello4-datapar-dist.chpl:
>>>
>>> config const numMessages = 100;
>>> const MessageSpace = {1..numMessages} dmapped Cyclic(startIdx=1);
>>> forall msg in MessageSpace do
>>> writeln("Hello, world! (from iteration ", msg, " of ", numMessages,
>>> "owned by locale ", here.id, " of ", numLocales, ")");
>>>
>>> Here, after the domain is dmapped, the MessageSpace will be
>>> distributed.
>>> For example, we have 10 nodes, and 2 cores per node. Will the forall loop
>>> ends up getting a parallelism of 20 ?
>>>
>>> I ran it and the output is in arbitary order, so does the forall
>>> implicitly
>>> enable both the parallelism among locales and the parallelism within a
>>> single locale ? In other words, does it actually have similar effect as
>>> the
>>> following style:
>>> coforall loc in Locales {
>>> on loc {
>>> for msg in local_MessageSpace {
>>> writeln();
>>> }
>>> }
>>> }
>>> *the local_MessageSpace will be determined by here.id, MessageSpace and
>>> the
>>> domain mapping it uses(e.g Cyclic), sometimes hard to determne
>>>
>>> Thanks !
>>>
>>> --
>>> Best regards
>>>
>>>
>>> Hui Zhang
>>>
>>
--
Best regards
Hui Zhang
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