Communicator

class Communicator

Wrapper around MPI_Comm

Subclassed by mpicpp_lite::CartesianCommunicator

Public Functions

inline Communicator()

Create MPI_COMM_WORLD communicator.

inline Communicator(const MPI_Comm &comm)

Create communicator from an MPI_Comm one.

inline Communicator(const Communicator &comm)

Copy constructor.

inline void free()

Marks the communicator object for deallocation.

inline int rank() const

Determine the rank of the executing process in a communicator.

Returns:

Rank of the executing process

inline int size() const

Determine the number of processes in a communicator.

Returns:

Number of processes

inline CartesianCommunicator create_cartesian(const std::vector<int> &dims, bool reorder = false) const

Makes a new communicator to which topology information has been attached.

Parameters:

• dims – Number of processes in each dimension

• reorder – Allow the function to reorder the processes

inline Group group() const

Accesses the group associated with given communicator.

Returns:

Group corresponding to communicator

template<typename T>
inline void send(int dest, int tag, const T &value) const

Send data to another process.

Template Parameters:

T – C++ type of the data

Parameters:

• dest – Destination rank

• tag – Message tag

• value – Value to send

template<typename T>
inline void send(int dest, int tag, const T *values, int n) const

Send data to another process.

Template Parameters:

T – C++ type of the data

Parameters:

• dest – Destination rank

• tag – Message tag

• values – Values to send

• n – Number of values to send

template<typename T, typename A>
inline void send(int dest, int tag, const std::vector<T, A> &value) const

Send std::vector of data to another process.

Template Parameters:

T – C++ type of the data

Parameters:

• dest – Destination rank

• tag – Message tag

• value – Vector of T to send

inline void send(int dest, int tag) const

Send a message to another process without any data.

Parameters:

• dest – Destination rank

• tag – Message tag

template<typename T>
inline Status recv(int source, int tag, T &value) const

Receive data from a remote process.

Template Parameters:

T – C++ type of the data

Parameters:

• source – Source rank

• tag – Message tag

• value – Variable to recieve the data

Returns:

Status of the operation

template<typename T>
inline Status recv(int source, int tag, T *values, int n) const

Receive data from a remote process.

Template Parameters:

T – C++ type of the data

Parameters:

• source – Source rank

• tag – Message tag

• values – Variable to recieve the data

• n – Number of values to receive

Returns:

Status of the operation

template<typename T, typename A>
inline Status recv(int source, int tag, std::vector<T, A> &value) const

Receive std::vector of data from a remote process.

Template Parameters:

T – C++ type of the data

Parameters:

• source – Source rank

• tag – Message tag

• value – Variable to recieve the data

Returns:

Status of the operation

inline Status recv(int source, int tag) const

Receive a message from a remote process without any data.

Parameters:

• source – Source rank

• tag – Message tag

Returns:

Status of the operation

template<typename T>
inline Request isend(int dest, int tag, const T &value) const

Send a message to a remote process without blocking.

Template Parameters:

T – C++ type of the data

Parameters:

• dest – Destination rank

• tag – Message tag

• value – Value to send

Returns:

Communication Request

template<typename T, typename A>
inline Request isend(int dest, int tag, const std::vector<T, A> &values) const

Send a std::vector of values to a remote process without blocking.

Template Parameters:

T – C++ type of the data

Parameters:

• dest – Destination rank

• tag – Message tag

• value – Values to send

Returns:

Communication Request

template<typename T>
inline Request isend(int dest, int tag, const T *values, int n) const

Send a message to a remote process without blocking.

Template Parameters:

T – C++ type of the data

Parameters:

• dest – Destination rank

• tag – Message tag

• values – Values to send

• n – Number of values to send

Returns:

Communication Request

template<typename T>
inline Request irecv(int source, int tag, T &value) const

Receive a message from a remote process without blocking.

Template Parameters:

T – C++ type of the data

Parameters:

• source – Source rank

• tag – Message tag

• value – Variable to recieve the data

Returns:

Communication Request

template<typename T>
inline Request irecv(int source, int tag, T *values, int n) const

Receive a message from a remote process without blocking.

Template Parameters:

T – C++ type of the data

Parameters:

• source – Source rank

• tag – Message tag

• values – Variable to recieve the data

• n – Number of values to receive

inline bool iprobe(int source, int tag) const

Nonblocking test for a message.

Parameters:

• source – Rank of source or ANY_SOURCE

• tag – Message tag or ANY_TAG

Returns:

true if a message with the specified source, and tag is available, false otherwise

inline bool iprobe(int source, int tag, Status &status) const

Nonblocking test for a message.

Parameters:

• source – Rank of source or ANY_SOURCE

• tag – Message tag or ANY_TAG

• status – Status object

Returns:

true if a message with the specified source, and tag is available, false otherwise

inline void barrier() const

Wait for all processes within a communicator to reach the barrier.

template<typename T>
inline void broadcast(T &value, int root) const

Broadcast a value from a root process to all other processes.

Template Parameters:

T – C++ type of the data

Parameters:

• value – Value to send

• root – Rank of the sending process

template<typename T>
inline void broadcast(std::vector<T> &value, int root) const

Broadcast a std::vector of values from a root process to all other processes.

Template Parameters:

T – C++ type of the data

Parameters:

• value – Value to send

• root – Rank of the sending process

template<typename T>
inline void broadcast(T *values, int n, int root) const

Broadcast a value from a root process to all other processes.

Template Parameters:

T – C++ type of the data

Parameters:

• values – Values to send

• n – Number of values to send

• root – Rank of the sending process

template<typename KEY, typename VALUE>
inline void broadcast(std::map<KEY, VALUE> &map, int root) const

Broadcast a map from a root process to all other processes.

Template Parameters:

• KEY – Key in the map

• VALUE – Value in the map

Parameters:

• map – map to send

• root – Rank of the sending process

template<typename T>
inline void gather(const T &in_value, T *out_values, int root) const

Gather together values from a group of processes.

Template Parameters:

T – C++ type of the data

Parameters:

• in_value – Value to send

• out_values – Receiving variable

• root – Rank of receiving process

template<typename T>
inline void gather(const T &in_value, std::vector<T> &out_values, int root) const

Gather together values from a group of processes.

Template Parameters:

T – C++ type of the data

Parameters:

• in_value – Value to send

• out_values – Receiving variable

• root – Rank of receiving process

template<typename T>
inline void gather(const T *in_values, int n, T *out_values, int root) const

Gather together values from a group of processes.

Template Parameters:

T – C++ type of the data

Parameters:

• in_values – Values to send

• n – Number of values to send

• out_values – Receiving variable

• root – Rank of receiving process

template<typename T>
inline void gather(const T *in_values, int n, std::vector<T> &out_values, int root) const

Gather together values from a group of processes.

Template Parameters:

T – C++ type of the data

Parameters:

• in_values – Values to send

• n – Number of values to send

• out_values – Receiving variable

• root – Rank of receiving process

template<typename T>
inline void gather(const std::vector<T> &in_values, std::vector<T> &out_values, const std::vector<int> &out_counts, const std::vector<int> &out_offsets, int root) const

Gather together values from a group of processes.

Template Parameters:

T – C++ datatype

Parameters:

• in_values[in] – Values to send

• out_values[out] – Buffer to receive the data

• out_counts[in] – Integer array (of length group size) containing the number of elements that are to be received from each process

• out_offsets[in] – Integer array (of length group size). Entry i specifies the displacement (relative to out_values) at which to place the incoming data from process i

• root – Rank of receiving process

template<typename T>
inline void all_gather(const T *in_value, int n, T *out_values, int m) const

Gathers data from all tasks and distribute the combined data to all tasks.

Template Parameters:

T – C++ type of the data

Parameters:

• in_value – Value to send

• n – Number of values to send

• out_values – Receiving variable

• m – Number of values to receive

template<typename T>
inline void all_gather(const T &in_value, std::vector<T> &out_values) const

Gathers data from all tasks and distribute the combined data to all tasks.

Template Parameters:

T – C++ type of the data

Parameters:

• in_value – Value to send

• out_values – Receiving variable

template<typename T>
inline void all_gather(const std::vector<T> &in_value, std::vector<T> &out_values) const

Gathers data from all tasks and distribute the combined data to all tasks.

Template Parameters:

T – C++ type of the data

Parameters:

• in_value – Vector of values to send (the size of this vector can be different on every process)

• out_values – Receiving variable

template<typename T>
inline void all_gather(const std::vector<T> &in_values, std::vector<T> &out_values, const std::vector<int> &out_counts, const std::vector<int> &out_offsets) const

Gathers data from all tasks and deliver the combined data to all tasks.

Template Parameters:

T – C++ datatype

Parameters:

• in_values[in] – Values to send

• out_values[out] – Buffer to receive the data

• out_counts[in] – Integer array (of length group size) containing the number of elements that are to be received from each process

• out_offsets[in] – Integer array (of length group size). Entry i specifies the displacement (relative to out_values) at which to place the incoming data from process i

template<typename T>
inline void scatter(const T *in_values, T &out_value, int root) const

Send data from one process to all other processes in a communicator.

Template Parameters:

T – C++ type of the data

Parameters:

• in_values – Values to send

• out_value – Receiving variable

• root – Rank of the sending process

template<typename T>
inline void scatter(const std::vector<T> &in_values, T &out_value, int root) const

Send data from one process to all other processes in a communicator.

Template Parameters:

T – C++ type of the data

Parameters:

• in_values – Values to send

• out_value – Receiving variable

• root – Rank of the sending process

template<typename T>
inline void scatter(const T *in_values, T *out_values, int n, int root) const

Send data from one process to all other processes in a communicator.

Template Parameters:

T – C++ type of the data

Parameters:

• in_values – Values to send

• out_values – Receiving variable

• n – Number of values to send

• root – Rank of the sending process

template<typename T>
inline void scatter(const std::vector<T> &in_values, T *out_values, int n, int root) const

Send data from one process to all other processes in a communicator.

Template Parameters:

T – C++ type of the data

Parameters:

• in_values – Values to send

• out_values – Receiving variable

• n – Number of values to send

• root – Rank of the sending process

template<typename T, typename Op>
inline void reduce(const T *in_values, int n, T *out_values, Op op, int root) const

Reduce values on all processes to a single value.

Template Parameters:

• T – C++ type of the data

• Op – Type of the reduce operation

Parameters:

• in_values – Values to send

• n – Number of values to send

• out_values – Receiving variable

• op – Reduce operation

• root – Rank of root process

template<typename T, typename Op>
inline void reduce(std::vector<T> const &in_values, std::vector<T> &out_values, Op op, int root) const

Reduce values on all processes to a single value.

Template Parameters:

• T – C++ type of the data

• Op – Type of the reduce operation

Parameters:

• in_values – Values to send

• out_values – Receiving variable

• op – Reduce operation

• root – Rank of root process

template<typename T, typename Op>
inline void reduce(const T &in_value, T &out_value, Op op, int root) const

Reduce values on all processes to a single value.

Template Parameters:

• T – C++ type of the data

• Op – Type of the reduce operation

Parameters:

• in_value – Values to send

• out_value – Receiving variable

• op – Reduce operation

• root – Rank of root process

template<typename T, typename Op>
inline void all_reduce(const T *in_values, int n, T *out_values, Op op) const

Combine values from all processes and distributes the result back to all processes.

Template Parameters:

• T – C++ type of the data

• Op – Type of the reduce operation

Parameters:

• in_values – Values to send

• n – Number of values to send

• out_values – Receiving variable

• op – Reduce operation

template<typename T, typename Op>
inline void all_reduce(const std::vector<T> &in_values, std::vector<T> &out_values, Op op) const

Combine values from all processes and distributes the result back to all processes.

Template Parameters:

• T – C++ type of the data

• Op – Type of the reduce operation

Parameters:

• in_values – Values to send

• out_values – Receiving variable

• op – Reduce operation

template<typename T, typename Op>
inline void all_reduce(const T &in_value, T &out_value, Op op) const

Combine values from all processes and distributes the result back to all processes.

Template Parameters:

• T – C++ type of the data

• Op – Type of the reduce operation

Parameters:

• in_value – Values to send

• out_value – Receiving variable

• op – Reduce operation

template<typename T, typename Op>
inline void all_reduce(T &value, Op op) const

Combine values from all processes and distributes the result back to all processes.

Template Parameters:

• T – C++ type of the data

• Op – Type of the reduce operation

Parameters:

• value – Send/receive variable

• op – Reduce operation

template<typename T>
inline void all_to_all(const T *in_values, int n, T *out_values, int m) const

Sends data from all to all processes.

Template Parameters:

T – C++ type of the data

Parameters:

• in_values – Values to send

• n – Number valus to send

• out_values – Receiving variable

• m – Values to receive

template<typename T>
inline void all_to_all(const std::vector<T> &in_values, std::vector<T> &out_values) const

Sends data from all to all processes.

Template Parameters:

T – C++ type of the data

Parameters:

• in_values – Values to send

• out_values – Receiving variable

template<typename T>
inline void all_to_all(const std::vector<std::vector<T>> &in_values, std::vector<T> &out_values) const

Sends data from all to all processes.

template<typename T>
inline void all_to_all(const std::vector<T> &in_values, const std::vector<int> &in_counts, const std::vector<int> &in_offsets, std::vector<T> &out_values, const std::vector<int> &out_counts, const std::vector<int> &out_offsets) const

Sends data from all to all processes; each process may send a different amount of data and provide displacements for the input and output data.

Template Parameters:

T – C++ datatype

Parameters:

• in_values[in] – Values to send

• in_counts[in] – Integer array equal to the group size specifying the number of elements to send to each processor

• in_offsets[in] – integer array (of length group size). Entry j specifies the displacement relative to sendbuf from which to take the outgoing data destined for process j

• out_values[out] – Buffer that will receive the data

• out_counts[in] – Integer array equal to the group size specifying the maximum number of elements that can be received from each processor

• out_offsets[in] – Integer array (of length group size). Entry i specifies the displacement relative to recvbuf at which to place the incoming data from process i

inline Communicator split(int color, int key) const

Split a communicator.

Parameters:

• color – Control of subset assignment. Processes with the same color are in the same new communicator

• key – Control of rank assignment. This is the rank of the calling process in the new communicator

template<typename T, typename Op>
inline void scan(const T *in_values, int n, T *out_values, Op op) const

Computes the scan (partial reductions) of data on a collection of processes.

Template Parameters:

• T – C++ type of the data

• Op – Type of the reduction operation

Parameters:

• in_values – Values to perform the scan on

• n – Number of values to scan (size of in_values)

• out_values – Receiving variable

• op – Reduce operation

template<typename T, typename Op>
inline void scan(const std::vector<T> &in_values, std::vector<T> &out_values, Op op) const

Computes the scan (partial reductions) of data on a collection of processes.

Template Parameters:

• T – C++ type of the data

• Op – Type of the reduction operation

Parameters:

• in_values – Values to perform the scan on

• out_values – Receiving variable

• op – Reduce operation

template<typename T, typename Op>
inline void scan(const T &in_value, T &out_value, Op op) const

Computes the scan (partial reductions) of data on a collection of processes.

Template Parameters:

• T – C++ type of the data

• Op – Type of the reduction operation

Parameters:

• in_value – Value to perform the scan on

• out_value – Receiving variable

• op – Reduce operation

template<typename T, typename Op>
inline void exscan(const T *in_values, int n, T *out_value, Op op) const

Computes the exclusive scan (partial reductions) of data on a collection of processes.

Template Parameters:

• T – C++ type of the data

• Op – Type of the reduction operation

Parameters:

• in_values – Values to perform the scan on

• n – Number of values to scan (size of in_values)

• out_value – Receiving variable

• op – Reduce operation

template<typename T, typename Op>
inline void exscan(const std::vector<T> &in_values, std::vector<T> &out_values, Op op) const

Computes the exclusive scan (partial reductions) of data on a collection of processes.

Template Parameters:

• T – C++ type of the data

• Op – Type of the reduction operation

Parameters:

• in_values – Values to perform the scan on

• out_values – Receiving variable

• op – Reduce operation

template<typename T, typename Op>
inline void exscan(const T &in_value, T &out_value, Op op) const

Computes the exclusive scan (partial reductions) of data on a collection of processes.

Template Parameters:

• T – C++ type of the data

• Op – Type of the reduction operation

Parameters:

• in_value – Value to perform the scan on

• out_value – Receiving variable

• op – Reduce operation

inline void abort(int errcode) const

Abort all tasks in the group of this communicator.

Parameters:

errcode – Error code to return to invoking environment

inline operator MPI_Comm() const

Cast operator so we can pass this directly in MPI API.

inline operator bool() const

Check if communicator.