Charm++ parallel programming system

[Phil Miller <mille121 AT illinois.edu>]

Hi Pascal,

Charm++ does not provide an API for querying whether a given array element exists or not. The reason for this is that Charm++ applications are expected to run in distributed environments, in which the response to such a query can vary unpredictably in time. For instance, the message carrying such a query might race with a message that would insert or delete such an element. In general, I would recommend constructing your parallel algorithm so that it does not need to make such queries.

In the specific case where you want to construct a particular element where it does not already exist, Charm++ offers 'on-demand creation' of chare array elements. This lets applications tag certain entry methods with one of the [createhome] or [createhere] attributes. When one of those entry methods is invoked on a given array index, the runtime system guarantees that the associated message will either be delivered to the element at that index, or will default construct that element and then deliver that message to it. More detail on how this works can be found in our manual.

Phil

On Wed, Jun 18, 2014 at 5:01 PM, Pascal <zetwal AT gmail.com> wrote:

Hello

I have a chare array like this:

array [1D] Node{

...

}

in which I put in values of type Node. Initially there is only one chare but then the chare generates other chares which in turn generate other chares (and deletes itself) which are inserted at specific locations in the array. Thus there might be gaps in the array. 

Is there a way for me to query the array like this: thisProxy[randomIndex] and it will tell me if there is an element in that location or not?

In other words, how do I know if a chare exists in a chare array?

Thanks

Cheers,
Pascal

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