[jira] Commented: (MAHOUT-435) Add assign(DenseVector)/assign(DenseMatrix) function to DenseVector/DenseMatrix

["Ted Dunning (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAHOUT-435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12885590#action_12885590 ] 

Ted Dunning commented on MAHOUT-435:
------------------------------------


Max, can you test to see how much difference the lack of allocation actually makes to your code?  We should still add this patch, but it will help us all to have a reference point regarding how much difference it makes.

My question really pertains to the cost of relatively large highly ephemeral (on average) allocations.  Since there is quite a bit of work that goes on with the contents of the copy, it may be that the cost of allocating and then almost always collecting the copy would be very small.
 

> Add assign(DenseVector)/assign(DenseMatrix) function to DenseVector/DenseMatrix
> -------------------------------------------------------------------------------
>
>                 Key: MAHOUT-435
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-435
>             Project: Mahout
>          Issue Type: New Feature
>          Components: Math
>            Reporter: Max Heimel
>            Priority: Minor
>         Attachments: MAHOUT-435.diff
>
>
> This new feature would add a new overloaded assign function to (Dense)Vector/(Dense)Matrix, that allows to assign the content of another (Dense)Vector / (Dense)Matrix by overwriting the content of the internal double array. Compared to using .clone(), this feature would reduce the number of memory allocations. 
> For example in case of an iterative algorithm, that needs to check for convergence;
> {code:title=Convergence check using .clone()|borderStyle=solid}
> Densematrix newMatrix = oldMatrix.clone();
> while(!converged)
> {
>     // perform iteration computation on newMatrix
>     converged=checkConvergence(newMatrix,oldMatrix);
>     oldMatrix = newMatrix.clone(); // results in memory allocation
> }
> {code}
> {code:title=Convergence check using .assign(Matrix)|borderStyle=solid}
> Densematrix newMatrix = oldMatrix.clone();
> while(!converged)
> {
>     // perform iteration computation on newMatrix
>     converged=checkConvergence(newMatrix,oldMatrix);
>     oldMatrix.assign(newMatrix); // no memory allocation
> }
> {code}

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.