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Lab1-1.md

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+[TOC]
+
+---
+
+## 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
+
+---
+
+##### MPI_Init
+
+`MPI_Init` — Initializes the MPI execution environment.
+
+```c
+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).
+
+---
+
+##### MPI_Comm_size
+
+`MPI_Comm_size` — Returns the size of the group associated with a communicator.
+
+```c
+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).
+
+---
+
+##### MPI_Comm_rank
+
+`MPI_Comm_rank` — Determines the rank of the calling process in the communicator.
+
+```c
+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).
+
+---
+
+##### MPI_Send
+
+`MPI_Send` — Performs a standard-mode blocking send.
+
+```c
+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).
+
+---
+
+##### MPI_Recv
+
+`MPI_Recv` — Performs a standard-mode blocking receive.
+
+```c
+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).
+
+---
+
+##### MPI_Finalize
+
+`MPI_Finalize` — Terminates MPI execution environment.
+
+```c
+int MPI_Finalize()
+```
+
+OUTPUT PARAMETER
+
+- `ierror`: Fortran only: Error status (integer).
+
+#### MPI程序编译运行
+
+```bash
+$ 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：
+```bash
+Greetings from process 0 of 4!
+Greetings from process 1 of 4!
+Greetings from process 2 of 4!
+Greetings from process 3 of 4!
+```
+
+---
+
+开始你的任务吧，祝你成功！