MPITypecreateh

MPI_Type_create_hindexed is a function in the Message Passing Interface (MPI) standard, designed for creating a new MPI datatype by indexing into an existing datatype. This function is particularly useful when dealing with non-contiguous data structures, such as sparse matrices or irregular arrays.

The function prototype is as follows:

int MPI_Type_create_hindexed(int count, const int array_of_blocklengths[], const MPI_Aint array_of_displacements[], MPI_Datatype oldtype, MPI_Datatype *newtype)

Here's a breakdown of the parameters:

- count: The number of blocks in the new datatype.

- array_of_blocklengths: An array of integers, where each element specifies the number of elements in the corresponding block.

- array_of_displacements: An array of MPI_Aint, where each element specifies the displacement (in bytes) of the corresponding block from the start of the old datatype.

- oldtype: The existing MPI datatype from which the new datatype is derived.

- newtype: A pointer to the new MPI datatype that is created.

The function returns an error code, which is MPI_SUCCESS if the operation is successful.

After creating the new datatype, it is typically committed using MPI_Type_commit before it can be used in communication operations. Once committed, the new datatype can be used in MPI send and receive operations, just like any other MPI datatype.

MPI_Type_create_hindexed is a powerful tool for handling complex data structures in parallel computing, enabling efficient and flexible communication patterns. However, it requires careful management of displacements and block lengths to avoid errors and ensure correct data transmission.