|
|
[TOC]
|
|
|
|
|
|
---
|
|
|
|
|
|
## MPI中的集合通信与广播
|
|
|
|
|
|
### 任务描述
|
|
|
|
|
|
本关任务：使用MPI中的`MPI_Reduce`和`MPI_Bcast`函数实现用户自定义输入的梯形法则近似计算积分面积。
|
|
|
|
|
|
### 相关知识
|
|
|
|
|
|
为了完成本关任务，你需要掌握：1.MPI中的梯形法则，2.如何使用`MPI_Bcast`集合通信函数将单个进程的数据发送到通信域中所有进程，3如何使用`MPI_Reduce`集合通信函数将通信域中所有进程的数据汇总。
|
|
|
|
|
|
#### 梯形法则
|
|
|
|
|
|
<img width="100%" src="/api/attachments/WUpBQ3hFN3ZwY1FLcE1RWWdhU010dz09?type=image/png)" alt="" />
|
|
|
|
|
|
梯形法则是指为了计算图（a）中从`a`到`b`阴影部分的面积，将该区域划分为`n`个子区域，每个子区域用梯形面积计算公式计算，最终将`n`个小梯形汇总求和作为所求面积大小的近似结果。
|
|
|
|
|
|
#### MPI_Bcast
|
|
|
|
|
|
`MPI_Bcast` - Broadcasts a message from the process with rank root to all other processes of the group.
|
|
|
|
|
|
```c
|
|
|
int MPI_Bcast(void *buffer, int count, MPI_Datatype datatype,
|
|
|
int root, MPI_Comm comm)
|
|
|
```
|
|
|
|
|
|
INPUT/OUTPUT PARAMETERS
|
|
|
|
|
|
- `buffer`: Starting address of buffer (choice).
|
|
|
- `count`: Number of entries in buffer (integer).
|
|
|
- `datatype`: Data type of buffer (handle).
|
|
|
- `root`: Rank of broadcast root (integer).
|
|
|
- `comm`: Communicator (handle).
|
|
|
- `info`: Info (handle, persistent only).
|
|
|
|
|
|
OUTPUT PARAMETERS
|
|
|
|
|
|
- `request`: Request (handle, non-blocking and persistent only).
|
|
|
- `ierror`: Fortran only: Error status (integer).
|
|
|
|
|
|
#### MPI_Reduce
|
|
|
|
|
|
`MPI_Reduce` - Reduces values on all processes within a group.
|
|
|
|
|
|
```c
|
|
|
int MPI_Reduce(const void *sendbuf, void *recvbuf, int count,
|
|
|
MPI_Datatype datatype, MPI_Op op, int root,
|
|
|
MPI_Comm comm)
|
|
|
```
|
|
|
|
|
|
INPUT PARAMETERS
|
|
|
|
|
|
- `sendbuf`: Address of send buffer (choice).
|
|
|
- `count`: Number of elements in send buffer (integer).
|
|
|
- `datatype`: Data type of elements of send buffer (handle).
|
|
|
- `op`: Reduce operation (handle).
|
|
|
- `root`: Rank of root process (integer).
|
|
|
- `comm`: Communicator (handle).
|
|
|
- `info`: Info (handle, persistent only).
|
|
|
|
|
|
OUTPUT PARAMETERS
|
|
|
|
|
|
- `recvbuf`: Address of receive buffer (choice, significant only at root).
|
|
|
- `request`: Request (handle, non-blocking and persistent only).
|
|
|
- `ierror`: Fortran only: Error status (integer).
|
|
|
|
|
|
### 编程要求
|
|
|
|
|
|
根据提示，在右侧编辑器补充两处注释部分代码，计算并输出阴影面积的大小。
|
|
|
|
|
|
### 测试说明
|
|
|
|
|
|
平台会对你编写的代码进行测试：
|
|
|
|
|
|
测试输入：`0 3 1024`；
|
|
|
预期输出：
|
|
|
`9.000`
|
|
|
|
|
|
测试输入：`1 7 2048`；
|
|
|
预期输出：
|
|
|
`114.000`
|
|
|
|
|
|
---
|
|
|
|
|
|
开始你的任务吧，祝你成功！
|
