[jira] [Resolved] (MATH-1530) Spline interpolation : Avoid recomputing indexes when possible

["Gilles Sadowski (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MATH-1530?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Gilles Sadowski resolved MATH-1530.
-----------------------------------
    Fix Version/s: 4.0
       Resolution: Done

Suggestion implemented (for {{SplineInterpolator}}) in commit 9c6ed8311fcb30518cc8935146d72a5b9126d41c ("master" branch).


> Spline interpolation : Avoid recomputing indexes when possible
> --------------------------------------------------------------
>
>                 Key: MATH-1530
>                 URL: https://issues.apache.org/jira/browse/MATH-1530
>             Project: Commons Math
>          Issue Type: Improvement
>            Reporter: Yassine Damerdji
>            Priority: Minor
>             Fix For: 4.0
>
>
> In org.apache.commons.math4.analysis.interpolation.SplineInterpolator and in org.apache.commons.math4.analysis.interpolation.AkimaSplineInterpolator, many indices are recomputed many times.
> Example :
> {code:java}
> for (int i = 1; i < n; i++) {
>     g = 2d * (x[i+1] - x[i - 1]) - h[i - 1] * mu[i -1];
>     mu[i] = h[i] / g;
> }{code}
> can be replaced by :
> {code:java}
> while (i < n) {
>     g[i] = 2d * (x[iPlusOne] - x[iMinusOne]) - h[iMinusOne] * mu[iMinusOne];
>     mu[i] = h[i] / g[i];
>     iMinusOne = i;
>     i = iPlusOne;
>     iPlusOne = iPlusOne + 1;
> }
> {code}
> In my tests, I saved almost 2% of processing time with this optimization.



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