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# System prepended metadata

title: Something we have to know(maybe)

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# Something we have to know(maybe)

[TOC]

## NCCL
* [NVIDIA](https://developer.nvidia.com/nccl)
* [introduction](https://on-demand.gputechconf.com/gtc/2018/video/S8462/)
### [Horovod](https://horovod.readthedocs.io/en/stable/)
* Horovod is combining NCCL and MPI into an wrapper for Distributed Deep Learning in for example TensorFlow.
* It can detect if GPU Direct via RDMA makes sense in the current hardware topology and uses it transparently.
* [on github](https://github.com/horovod/horovod)

### MPI
* [Message Passing Interface](https://zh.wikipedia.org/wiki/%E8%A8%8A%E6%81%AF%E5%82%B3%E9%81%9E%E4%BB%8B%E9%9D%A2)
* 訊息傳遞介面是一個平行計算的應用程式介面（API），常在超級電腦、電腦叢集等非共享記憶體環境程式設計。