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

["Max Heimel (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MAHOUT-435?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Max Heimel updated MAHOUT-435:
------------------------------

    Description: 
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}

  was:
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 existing 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}


> 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
>
> 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}

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