CCZU/Lab1-1.md

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MPI程序基本框架与常用函数

任务描述

本关任务：练习MPI程序的基本框架与常用函数，包括MPI_Init、MPI_Comm_size、MPI_Comm_rank、MPI_Send、MPI_Recv以及MPI_Finalize的使用。

Open MPI 文档：https://docs.open-mpi.org/en/main/

相关知识

为了完成本关任务，你需要掌握：1.MPI程序的基本框架，2.MPI常用函数。

MPI常用函数

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MPI_Init

MPI_Init — Initializes the MPI execution environment.

int MPI_Init(int *argc, char ***argv)

INPUT PARAMETERS

• argc: C only: Pointer to the number of arguments.
• argv: C only: Argument vector.

OUTPUT PARAMETER

• ierror: Fortran only: Error status (integer).

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MPI_Comm_size

MPI_Comm_size — Returns the size of the group associated with a communicator.

int MPI_Comm_size(MPI_Comm comm, int *size)

INPUT PARAMETER

• comm: Communicator (handle).

OUTPUT PARAMETERS

• size: Number of processes in the group of comm (integer).

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MPI_Comm_rank

MPI_Comm_rank — Determines the rank of the calling process in the communicator.

int MPI_Comm_rank(MPI_Comm comm, int *rank)

INPUT PARAMETERS

• comm: Communicator (handle).

OUTPUT PARAMETERS

• rank: Rank of the calling process in group of comm (integer).
• ierror: Fortran only: Error status (integer).

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MPI_Send

MPI_Send — Performs a standard-mode blocking send.

int MPI_Send(const void *buf, int count, MPI_Datatype datatype, int dest,
     int tag, MPI_Comm comm)

INPUT PARAMETERS

• buf: Initial address of send buffer (choice).
• count: Number of elements in send buffer (nonnegative integer).
• datatype: Datatype of each send buffer element (handle).
• dest: Rank of destination (integer).
• tag: Message tag (integer).
• comm: Communicator (handle).

OUTPUT PARAMETER

• ierror: Fortran only: Error status (integer).

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MPI_Recv

MPI_Recv — Performs a standard-mode blocking receive.

int MPI_Recv(void *buf, int count, MPI_Datatype datatype,
     int source, int tag, MPI_Comm comm, MPI_Status *status)

INPUT PARAMETERS

• count: Maximum number of elements to receive (integer).
• datatype: Datatype of each receive buffer entry (handle).
• source: Rank of source (integer).
• tag: Message tag (integer).
• comm: Communicator (handle).

OUTPUT PARAMETERS

• buf: Initial address of receive buffer (choice).
• status: Status object (status).
• ierror: Fortran only: Error status (integer).

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MPI_Finalize

MPI_Finalize — Terminates MPI execution environment.

int MPI_Finalize()

OUTPUT PARAMETER

• ierror: Fortran only: Error status (integer).

MPI程序编译运行

$ mpicc -g -Wall -o mpi_hello mpi_hello.c
$ mpiexec -n 4 ./mpi_hello

编程要求

根据提示，在右侧编辑器补充六处代码。启动四个进程分别将问候语发送给进程0，由进程0将接收到的问候语打印输出出来。

测试说明

平台会对你编写的代码进行测试：

测试输入：无； 预期输出：

Greetings from process 0 of 4!
Greetings from process 1 of 4!
Greetings from process 2 of 4!
Greetings from process 3 of 4!

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开始你的任务吧，祝你成功！