Collective Communication¶

Located in file: MEL.hpp

void MEL::Bcast(void *ptr, const int num, const Datatype &datatype, const int root, const Comm &comm)¶

Broadcast an array to all processes in comm, where all processes know how many elements to expect.

See

MPI_Bcast

Parameters

• ptr -

  Pointer to the memory receive into

• num -

  The number of elements to broadcast

• datatype -

  The derived datatype of the elements to broadcast

• root -

  The rank of the process to send from

• comm -

  The comm world to broadcast within

void MEL::Scatter(void *sptr, const int snum, const Datatype &sdatatype, void *rptr, const int rnum, const Datatype &rdatatype, const int root, const Comm &comm)¶

Scatter an array to all processes in comm, where all processes know how many elements to expect.

See

MPI_Scatter

Parameters

• sptr -

  Pointer to the memory to scatter, significant only on root

• snum -

  The number of elements to scatter, significant only on root

• sdatatype -

  The derived datatype of the elements to send, significant only on root

• rptr -

  Pointer to the memory to receive into

• rnum -

  The number of elements to receive

• rdatatype -

  The derived datatype of the elements to receive

• root -

  The rank of the process to send from

• comm -

  The comm world to scatter within

void MEL::Scatterv(void *sptr, const int *snum, const int *displs, const Datatype &sdatatype, void *rptr, const int rnum, const Datatype &rdatatype, const int root, const Comm &comm)¶

Scatter an array to all processes in comm, where all processes have an independent number of elements to expect.

See

MPI_Scatterv

Parameters

• sptr -

  Pointer to the memory to scatter, significant only on root

• snum -

  Pointer to an array of number of elements to send to each process, significant only on root

• displs -

  Pointer to an array of the element displacements of where each processes data is to be sent, significant only on root

• sdatatype -

  The derived datatype of the elements to send, significant only on root

• rptr -

  Pointer to the memory to receive into

• rnum -

  The number of elements to receive

• rdatatype -

  The derived datatype of the elements to receive

• root -

  The rank of the process to send from

• comm -

  The comm world to scatter within

void MEL::Gather(void *sptr, const int snum, const Datatype &sdatatype, void *rptr, const int rnum, const Datatype &rdatatype, const int root, const Comm &comm)¶

Gather an array from all processes in comm.

See

MPI_Gather

Parameters

• sptr -

  Pointer to the memory to gather

• snum -

  The number of elements to gather

• sdatatype -

  The derived datatype of the elements to send

• rptr -

  Pointer to the memory to receive into, significant only on root

• rnum -

  The number of elements to receive, significant only on root

• rdatatype -

  The derived datatype of the elements to receive, significant only on root

• root -

  The rank of the process to send to

• comm -

  The comm world to gather within

void MEL::Gatherv(void *sptr, const int snum, const Datatype &sdatatype, void *rptr, const int *rnum, const int *displs, const Datatype &rdatatype, const int root, const Comm &comm)¶

Gather an array from all processes in comm, where all processes have an independent number of elements to send.

See

MPI_Gatherv

Parameters

• sptr -

  Pointer to the memory to gather

• snum -

  The number of elements to gather

• sdatatype -

  The derived datatype of the elements to send

• rptr -

  Pointer to the memory to receive into, significant only on root

• rnum -

  Pointer to an array of the number of elements to receive from each process, significant only on root

• displs -

  Pointer to an array of the displacements of elements to be received from each process, significant only on root

• rdatatype -

  The derived datatype of the elements to receive, significant only on root

• root -

  The rank of the process to send to

• comm -

  The comm world to gather within

void MEL::Allgather(void *sptr, const int snum, const Datatype &sdatatype, void *rptr, const int rnum, const Datatype &rdatatype, const Comm &comm)¶

Gather an array from all processes in comm and distribute it to all processes.

See

MPI_Allgather

Parameters

• sptr -

  Pointer to the memory to gather

• snum -

  The number of elements to gather

• sdatatype -

  The derived datatype of the elements to send

• rptr -

  Pointer to the memory to receive into

• rnum -

  The number of elements to receive

• rdatatype -

  The derived datatype of the elements to receive

• comm -

  The comm world to gather within

void MEL::Allgatherv(void *sptr, const int snum, const Datatype &sdatatype, void *rptr, const int *rnum, const int *displ, const Datatype &rdatatype, const Comm &comm)¶

Gather an array from all processes in comm and distribute it to all processes, where all processes have an independent number of elements to send.

See

MPI_Allgatherv

Parameters

• sptr -

  Pointer to the memory to gather

• snum -

  The number of elements to gather

• sdatatype -

  The derived datatype of the elements to send

• rptr -

  Pointer to the memory to receive into

• rnum -

  Pointer to an array of the number of elements to receive from each process

• displ -

  Pointer to an array of the element displacements of where each processes data is to be received

• rdatatype -

  The derived datatype of the elements to receive

• comm -

  The comm world to gather within

void MEL::Alltoall(void *sptr, const int snum, const Datatype &sdatatype, void *rptr, const int rnum, const Datatype &rdatatype, const Comm &comm)¶

Broadcast from all processes to all processes.

See

MPI_Alltoall

Parameters

• sptr -

  Pointer to snum elements to send

• snum -

  The number of elements to send

• sdatatype -

  The derived datatype of the elements to send

• rptr -

  Pointer to rnum * commsize elements to receive

• rnum -

  The number of elements to receive from each process in comm

• rdatatype -

  The derived datatype of the elements to receive

• comm -

  The comm world to broadcast within

void MEL::Alltoallv(void *sptr, const int *snum, const int *sdispl, const Datatype &sdatatype, void *rptr, const int *rnum, const int *rdispl, const Datatype &rdatatype, const Comm &comm)¶

Broadcast from all processes to all processes with independent number of elements for each process.

See

MPI_Alltoallv

Parameters

• sptr -

  Pointer to snum elements to send

• snum -

  Pointer to an array of the number of elements to send from each process

• sdispl -

  Pointer to an array of element displacements of where each processes data is to be sent from

• sdatatype -

  The derived datatype of the elements to send

• rptr -

  Pointer to the receive buffer

• rnum -

  Pointer to an array of the number of elements to receive from each process

• rdispl -

  Pointer to an array of element displacements of where each processes data is to be recieved to

• rdatatype -

  The derived datatype of the elements to receive

• comm -

  The comm world to broadcast within

void MEL::Alltoallw(void *sptr, const int *snum, const int *sdispl, const Datatype *sdatatype, void *rptr, const int *rnum, const int *rdispl, const Datatype *rdatatype, const Comm &comm)¶

Broadcast from all processes to all processes with independent derived datatypes and number of elements for each process.

See

MPI_Alltoallw

Parameters

• sptr -

  Pointer to snum elements to send

• snum -

  Pointer to an array of the number of elements to send from each process

• sdispl -

  Pointer to an array of element displacements of where each processes data is to be sent from

• sdatatype -

  Pointer to an array of the derived datatypes of the elements to send for each process

• rptr -

  Pointer to the receive buffer

• rnum -

  Pointer to an array of the number of elements to receive from each process

• rdispl -

  Pointer to an array of element displacements of where each processes data is to be recieved to

• rdatatype -

  Pointer to an array of the derived datatypes of the elements to receive for each process

• comm -

  The comm world to broadcast within

void MEL::Reduce(void *sptr, void *rptr, const int num, const Datatype &datatype, const Op &op, const int root, const Comm &comm)¶

Reduce an array of known length across all processes in comm using the given operation.

See

MPI_Reduce

Parameters

• sptr -

  Pointer to num elements to send

• rptr -

  Pointer to the receive buffer, significant only on root

• num -

  The number of elements in the array

• datatype -

  The derived datatype of the elements to reduce

• op -

  The operation to perform for the reduction

• root -

  The process to receive the result

• comm -

  The comm world to reduce within

void MEL::Allreduce(void *sptr, void *rptr, const int num, const Datatype &datatype, const Op &op, const Comm &comm)¶

Reduce an array of known length across all processes in comm using the given operation, and distribute the result to all processes.

See

MPI_Allreduce

Parameters

• sptr -

  Pointer to num elements to send

• rptr -

  Pointer to the receive buffer

• num -

  The number of elements in the array

• datatype -

  The derived datatype of the elements to reduce

• op -

  The operation to perform for the reduction

• comm -

  The comm world to reduce within

template <typename T>

void MEL::Bcast(T *ptr, const int num, const int root, const Comm &comm)¶

Broadcast an array to all processes in comm, where all processes know how many elements to expect.

Parameters

• ptr -

  Pointer to the memory receive into

• num -

  The number of elements to broadcast

• root -

  The rank of the process to send from

• comm -

  The comm world to broadcast within