[jira] [Commented] (GEOMETRY-10) Reuse Normalized Vectors

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

    [ https://issues.apache.org/jira/browse/GEOMETRY-10?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16605723#comment-16605723 ] 

Gilles commented on GEOMETRY-10:
--------------------------------

Implementation of {{normalize()}} in the description does not take [infinities into account|https://git1-us-west.apache.org/repos/asf?p=commons-math.git;a=blob;f=src/main/java/org/apache/commons/math4/util/MathArrays.java;h=0f7046ee0bf83073c18a2928752e6d21c4cf7152;hb=HEAD#l958].

bq. We'll need to verify that this won't introduce any floating point accuracy issues.

Perhaps this [implementation|https://git1-us-west.apache.org/repos/asf?p=commons-numbers.git;a=blob;f=commons-numbers-arrays/src/main/java/org/apache/commons/numbers/arrays/SafeNorm.java;h=a04fb4d1a5aef78fb4b10eb8d4d9dea5cff03780;hb=HEAD] should be used (?).


> Reuse Normalized Vectors
> ------------------------
>
>                 Key: GEOMETRY-10
>                 URL: https://issues.apache.org/jira/browse/GEOMETRY-10
>             Project: Apache Commons Geometry
>          Issue Type: Improvement
>            Reporter: Matt Juntunen
>            Priority: Minor
>
> The Vector.normalize() method is used quite frequently. We currently always return a new instance with each method call, but we should be able to reuse the current instance if it is already normalized. 
> Ex:
> {code:java}
> public Vector3D normalize() {
>    final double normSq = getNormSq();
>    if (normSq == 1.0) {
>       return this;
>    }
>    else if (normSq == 0.0) {
>       throw new IllegalStateException(ZERO_NORM_MSG);
>    }
>    return scalarMultiply(1 / Math.sqrt(normSq);
> }{code}
> We'll need to verify that this won't introduce any floating point accuracy issues.



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