[Mpi-forum] why (int)0x4c000101 ?

[Jeff Squyres]

You should probably ask on the MPICH mailing list -- this is the mailing list for the general MPI Forum itself.


On May 27, 2012, at 10:42 AM, ÄþÄþ ¶­ wrote:

> when I read mpich2-1.4.1 code, I saw code as follow:
> 
> Code:
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> typedef int MPI_Datatype;
> #define MPI_CHAR           ((MPI_Datatype)0x4c000101)
> #define MPI_SIGNED_CHAR    ((MPI_Datatype)0x4c000118)
> #define MPI_UNSIGNED_CHAR  ((MPI_Datatype)0x4c000102)
> #define MPI_BYTE           ((MPI_Datatype)0x4c00010d)
> #define MPI_WCHAR          ((MPI_Datatype)0x4c00040e)
> #define MPI_SHORT          ((MPI_Datatype)0x4c000203)
> #define MPI_UNSIGNED_SHORT ((MPI_Datatype)0x4c000204)
> #define MPI_INT            ((MPI_Datatype)0x4c000405)
> #define MPI_UNSIGNED       ((MPI_Datatype)0x4c000406)
> #define MPI_LONG           ((MPI_Datatype)0x4c000407)
> #define MPI_UNSIGNED_LONG  ((MPI_Datatype)0x4c000408)
> #define MPI_FLOAT          ((MPI_Datatype)0x4c00040a)
> #define MPI_DOUBLE         ((MPI_Datatype)0x4c00080b)
> #define MPI_LONG_DOUBLE    ((MPI_Datatype)0x4c000c0c)
> #define MPI_LONG_LONG_INT  ((MPI_Datatype)0x4c000809)
> #define MPI_UNSIGNED_LONG_LONG ((MPI_Datatype)0x4c000819)
> #define MPI_LONG_LONG      MPI_LONG_LONG_INT
> 
> Anyone can tell me what is the meaning of those hex values? and why does the author use them?
> why do they define "MPI_CHAR" as ((MPI_Datatype)0x4c000101) instead of "char"?
> thx
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-- 
Jeff Squyres
jsquyres at cisco.com
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