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Posted to dev@singa.apache.org by "wangwei (JIRA)" <ji...@apache.org> on 2015/09/26 17:14:04 UTC

[jira] [Resolved] (SINGA-71) Fix a buf from repeated averaging gradients from workers

     [ https://issues.apache.org/jira/browse/SINGA-71?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

wangwei resolved SINGA-71.
--------------------------
    Resolution: Fixed

> Fix a buf from repeated averaging gradients from workers
> --------------------------------------------------------
>
>                 Key: SINGA-71
>                 URL: https://issues.apache.org/jira/browse/SINGA-71
>             Project: Singa
>          Issue Type: Bug
>            Reporter: wangwei
>            Assignee: wangwei
>
> For workers from the same group, if they share parameters, gradients of parameters should be averaged. SINGA averages the gradients by
> * aggregates gradients from all workers
> * calls Updater::Update() passing the scale_grad = 1.0 / worker_group_size. 
> * The Update function multiplies the gradient with scale_grad.
> The bug was from the Trainer::HandleUpdate() which averaged the gradients from local workers. The bug has been fixed by removing the averaging operation. Gradients from local workers are (only) summed before sending to servers.



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