# ParallelComputing

**Repository Path**: wangqiyuejava63/parallel-computing

## Basic Information

- **Project Name**: ParallelComputing
- **Description**: Improve gray-scaling program with MPI and OpenMP
Analyze the performance of two methods of implementation.
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2025-12-20
- **Last Updated**: 2025-12-21

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# How to build
`make`

# How to run
`mpirun -np 16 grayscale_mpi im.ppm out.ppm`

`./grayscale_openmp im.ppm out.ppm`

`./grayscale_serial im.ppm out.ppm`


-np is to indicate the number of processor

# what is ppm
https://netpbm.sourceforge.net/doc/ppm.html

# MPI

## Install MPI

```sh
sudo apt-get install openmpi-bin libopenmpi-dev
```

if have install network problem
can change apt source according to this
https://mirrors.ustc.edu.cn/help/ubuntu.html#__tabbed_1_2


## How to use MPI
MPI 全名叫 Message Passing Interface，即信息传递接口，其作用是在不同进程间传递消息，从而可以并行地处理任务，即进行并行计算

https://xflops.sjtu.edu.cn/hpc-start-guide/parallel-computing/mpi/#mpi_2

https://mpitutorial.com/tutorials/mpi-scatter-gather-and-allgather/zh_cn/

### mpicc
mpicc 是一个 编译器包装器（compiler wrapper）；
它本身不编译代码，而是调用真正的编译器（这里是 /usr/bin/gcc）；
同时自动添加必要的参数，比如：
-I/usr/include/openmpi（包含 MPI 头文件）
-L/usr/lib/openmpi/lib（链接库路径）
-lmpi（链接 MPI 库）

# OpenMP

OpenMp提供了对并行算法的高层的抽象描述，程序员通过在源代码中加入专用的pragma来指明自己的意图，由此编译器可以自动将程序进行并行化，并在必要之处加入同步互斥以及通信。

普通执行顺序是串行执行，执行完一条指令才能执行下一条指令。
改成并行架构后，可以同时并行执行多条指令，在指令总数不变的情况下所需的总执行时间就会减小。

OpenMP采用fork-join的执行模式。开始的时候只存在一个主线程，当需要进行并行计算的时候，派生出若干个分支线程来执行并行任务。当并行代码执行完成之后，分支线程会合，并把控制流程交给单独的主线程。

## How to use OpenMP
https://www.oryoy.com/news/ubuntu-xi-tong-qing-song-an-zhuang-openmp-yi-bu-dao-wei-de-bian-yi-you-hua-zhi-nan.html

https://www.cnblogs.com/buptmuye/p/3711097.html
https://www.cnblogs.com/yangyangcv/archive/2012/03/23/2413335.html
https://www.cnblogs.com/carsonzhu/p/17131175.html


### some intersting things
I searched on Intel technical library 
https://www.intel.com/content/www/us/en/developer/technical-library/overview.html?q=openmp&s=Relevancy

and found this
https://www.intel.com/content/www/us/en/developer/videos/openmp-the-once-and-future-api.html

and this
https://www.intel.com/content/www/us/en/developer/videos/three-quick-practical-examples-openmp-offload-gpus.html

# Benchmark
## test
- get a serial runtime as a base
./test_serial.sh



./benchmark.sh -t -mpi
./benchmark.sh -s -mpi
./benchmark.sh -e -mpi

./benchmark.sh -t -omp
./benchmark.sh -s -omp
./benchmark.sh -e -omp

## store the output into txt
mpi_runtime.txt
mpi_speedup.txt
mpi_efficiency.txt

omp_runtime.txt
omp_speedup.txt
omp_efficiency.txt

## plot

python3 plot_mpi_omp.py -mpi -runtime
python3 plot_mpi_omp.py -mpi -speedup
python3 plot_mpi_omp.py -mpi -efficiency

python3 plot_mpi_omp.py -omp -runtime
python3 plot_mpi_omp.py -omp -speedup
python3 plot_mpi_omp.py -omp -efficiency

python3 plot_comparison.py

python3 plot_comparison_speedup_efficiency.py


> Traceback (most recent call last):
>  File "/home/wqy/ParallelComputing/./plot_mpi.py", line 1, in <module>
>    import matplotlib.pyplot as plt
> ModuleNotFoundError: No module named 'matplotlib'

- how to fix 

sudo apt install python3-pip

sudo apt install python3-matplotlib