On Wed, Dec 8, 2010 at 10:04 PM, Santosh Ansumali <ansum...@gmail.com> wrote:
> I am confused with the use of MPI derived datatype for classes with
> static member. How to create derived datatype for something like
> class test{
> static const int i=5;
> double data[5];
> }
>
This looks like C++ code, and I think there can be a couple of
problems with sending this as an MPI derived datatype:
- the "static" data member is shared between all instances of the
class, so it cannot be part of the MPI datatype (it will likely be
at a fixed memory location);
- in addition, the "i" member is "static const" of a POD type, meaning
the compiler is allowed to optimize it out and not allocate any
actual memory location for it;
This boils down to: the only data you need to send around in a "class
test" instance is the "double data[5]" array.
If the static member were not "const", you could send it in a separate
message.
Best regards,
Riccardo
P.S. Besides, all members in a "class" are private by default and
"class test" does not have a constructor, so there's no way you can
put any useful values into this "test" class. (But I guess this is
just an oversight when stripping down the code for the example...)
