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Posted to dev@singa.apache.org by "wangwei (JIRA)" <ji...@apache.org> on 2017/06/04 03:02:04 UTC

[jira] [Resolved] (SINGA-316) Add SigmoidCrossEntropy

     [ https://issues.apache.org/jira/browse/SINGA-316?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

wangwei resolved SINGA-316.
---------------------------
    Resolution: Fixed

> Add SigmoidCrossEntropy
> -----------------------
>
>                 Key: SINGA-316
>                 URL: https://issues.apache.org/jira/browse/SINGA-316
>             Project: Singa
>          Issue Type: New Feature
>            Reporter: wangwei
>            Assignee: wangwei
>
> SigmoidCrossEntropy is a loss function for samples with multiple labels.
> For each sample, denote the final layer's output as x (a vector of length L), 
> and y as the ground truth label vector (a binary vector of length L) 
> where L is the label set size. 
> SigmoidCrossEntropy computes 
> p_i = sigmoid(x_i)
> loss_i = -y_i log p_i -(1-y_i)log (1-p_i)
> A threshold t_i can be tuned to decide the label assignment, e.g. y_i = 1 if p_i > t_i.



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