Charm++ parallel programming system

[Abhinav Bhatele <bhatele AT illinoisalumni.org>]

Hello Sagar,

CkArrayMap is used by the runtime i.e. Charm++ to provide a default mapping of array elements to physical processors. You can override that default mapping by creating your own map as the kNeighbor code does below.

A user defined mapping consists of providing a function which given the CkArrayIndex for an array element returns the processor the element resides on. This function is called procNum and you have to define it for a customized mapping.

For most chare arrays (1D, 2D, 3D) you do not need to write your own map function.

Also an alternative way of providing a map, it to use insert(int pe) for each array element when you create an array. Please look in the charm manual for examples.

- Abhinav

On Fri, Aug 5, 2011 at 5:42 AM, SAGAR SHEDGE <sagar.shedge92 AT gmail.com> wrote:

Respected Sir/Mam,

  I was reading example from tests/charm++/kNeighbour/ , where I seen one syntax in .ci file.

group MyMap : CkArrayMap{
        entry MyMap(int);
    };

In .C file you have inherited MyMap from CkArrayMap and overloaded pure virtual function     int procNum(int arrayHdl, const CkArrayIndex &idx).

I have query as follows :

1. I want to know why you have written CkArrayMap there , as CkArrayMap structure is internally used by charm++ to map array element to home processor.
2. In which cases we have write it?
3. What is purpose of procNum(int arrayHdl, const CkArrayIndex &idx). i.e. what you have done in that function? Also I am sending you both files.


--
Sagar Dilip Shedge,
C-DAC R&D,
Pune.

 

With Regards.

 

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--
Abhinav Bhatele
Postdoctoral Research Staff Member
Center for Applied Scientific Computing
Lawrence Livermore National Laboratory