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From 陈海波 <hzchenha...@corp.netease.com>
Subject Re: Communication between GPUs
Date Tue, 21 Apr 2015 09:51:56 GMT
Hi~,
    In our preivious work of deep learning on GPU, we focus on parallel training of DNN(without
convolution layer) for our speech recognition.
It is't easy to adopt model parallelization strategy to speed training.And with the consideration
of transfering big model between node and 
node,so we decided to use a single node with multi-GPU for training. And we use CUDA APIs
For transfering messages between GPU and GPU
(both support GPUDirect and without GPUDirect).In our plan,it does not exits the problem of
multi node communication.
Some discussions:
1) We think cudamat is a good choice for linear algebra computataion. But we find you use
mshadow libraries to develop singa.
   As we know,mshadow can provide a GPU Matrix/Tensor Template libary,and it also support
some simple interfaces for Multi-GPU.So we think
we can go on using mshadow for linear algebra computataion on both GPU and CPU.
2)  we consult NVIDIA's officials and they give an answer that they are not sure whether ZeroMQ
supports GPUDirect and Infiniband or not,and
   they suggest us adopting OpenMPI.

   And I think we can discuss more.

thanks~

在2015-04-21 12:05:19,陈海波<hzchenhaibo@corp.netease.com>写道:
> As planed in the previous discussion, we are stabilizing the APIs of each
> module.
> One problem I am encountered is about the communication APIs to support
> GPUs.
> 
> We can use some libraries like cudamat (https://code.google.com/p/cudamat/)
> for linear algebra computation. Hence, the APIs on computation would almost
> the same as those for CPU. But I have poor knowledge on the communication
> between GPU and CPU, and the communication between GPUs.
> I am asking you for your suggestions.
> 
> Wangyuan, Wuwei and Haibo: Since you are working on deep learning using
> GPUs, it would be appreciated if you can give some feedback.
> 
> As far as I know that traditionally messages are transferred from GPU
> memory to CPU memory and then transferred through TCP/IP to other nodes and
> then transferred from CPU memory to GPU memory. We can easily support such
> communication using the current APIs for CPU. But the transferring between
> GPU and CPU would bring extra cost.
> NVDIA has provided a technique called GPUDirect, which enables directly
> message passing from GPU memory to network (e.g., infiniband) card. Some
> MPI variants now use this technique. But we have switched from MPI to
> ZeroMQ, we need to make sure that ZeroMQ supports GPUDirect and
> Infiniband.  Do you have any investigations on this? Or how do you
> implement the message transferring in your implementation?
> 
> Thanks.
> 
> regards,
> Wei

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