Charm++ parallel programming system

[Phil Miller <mille121 AT illinois.edu>]

On Tue, May 4, 2010 at 16:02, Abhishek Gupta 
<gupta59 AT illinois.edu>
 wrote:
> Also, is it possible to get the result of reduction on one of the chare
> array elements instead of the main chare ? The workaround is to get it on
> mainchare and then send it to appropriate array element.

Sure. Just change the callback that you pass to the reduction to refer
to one of your array element's entry methods.

> Abhishek
>
>
> On Tue, May 4, 2010 at 1:23 PM, Eric Bohm 
> <ebohm AT illinois.edu>
>  wrote:
>>
>> It should be noted that in the current implementation the delegated
>> CkMulticastMgr section multicast/reductions will significantly
>> outperform the 1d array broadcast/reductions at scale.  I really would
>> not recommend decomposing your problem into column arrays, especially if
>> you would expect them to span a subset of processors.  The current
>> (wrong in my opinion) default assumptions of anytime migration support
>> kills scaling performance for array broadcasts under those conditions.
>>
>> Filippo Gioachin wrote:
>> > Alternatively, you can chop your 2-D array into N 1-D array, then each
>> > can perform its own reduction. If you need to do multicasts that span
>> > more than one array, you can use a CProxySection spanning all the arrays
>> > you need.
>> > Filippo
>> >
>> > On Tue, May 4, 2010 at 08:04, Ramprasad Venkataraman 
>> > <ramv AT illinois.edu
>> > <mailto:ramv AT illinois.edu>>
>> >  wrote:
>> >
>> >     Delegate your sections to CkMulticast if you want section
>> > reductions.
>> >
>> >     Ram
>> >
>> >
>> >     On May 4, 2010, at 7:36 AM, Phil Miller 
>> > <mille121 AT illinois.edu
>> >     
>> > <mailto:mille121 AT illinois.edu>>
>> >  wrote:
>> >
>> >     > On Tue, May 4, 2010 at 01:10, Abhishek Gupta 
>> > <gupta59 AT illinois.edu
>> >     
>> > <mailto:gupta59 AT illinois.edu>>
>> >     > wrote:
>> >     >> I have a 2-D partitioned matrix and I want to do a reduction
>> > along x
>> >     >> dimension in this 2-D chare Array and this needs to be done for
>> > each
>> >     >> column.  What is the best way to do that ? Using array section
>> >     >> proxies ?
>> >     >
>> >     > Instinctively, I'm inclined to say that there's no baked-in
>> > support
>> >     > for that at present. Depending on how performance critical this
>> >     > reduction is, you may be best off implementing it in your
>> > application
>> >     > as "everyone sends to (0,y)" and have one element calculate the
>> >     > reduction, or by manually sending the data up a tree.
>> >     >
>> >     > It looks like the libraries in
>> >     > src/libs/ck-libs/{sparseReducer,sparseContiguousReducer} may serve
>> >     > your purpose.
>> >     >
>> >     > _______________________________________________
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>> >  
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>> >     >
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>> >
>> >
>> >
>> > --
>> > Filippo Gioachin
>> > PhD Candidate
>> > Department of Computer Science
>> > University of Illinois at Urbana-Champaign
>> > Ph: +1-217-333-4764
>> >
>> >
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