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https://issues.apache.org/jira/browse/MAHOUT-300?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12836167#action_12836167
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Robin Anil commented on MAHOUT-300:
-----------------------------------
I removed hasNoElements check as per sean's and teds comment
the current fix is as follows. See the maxIndex implementation. I dont know
what to do in the edge case of vector being negative valued and sparse. We
could return -1 or first index of 0;
{code}
public double maxValue() {
double result = Double.NEGATIVE_INFINITY;
Iterator<Element> iter = this.iterateNonZero();
while (iter.hasNext()) {
Element element = iter.next();
result = Math.max(result, element.get());
}
if (getNumNondefaultElements() < size()) return Math.max(result, 0.0);
return result;
}
public int maxValueIndex() {
int result = -1;
double max = Double.NEGATIVE_INFINITY;
Iterator<Element> iter = this.iterateNonZero();
while (iter.hasNext()) {
Element element = iter.next();
double tmp = element.get();
if (tmp > max) {
max = tmp;
result = element.index();
}
}
// if the maxElement is negative and the vector is sparse then any
// unfilled element(0.0) could be the maxValue hence return -1;
if (getNumNondefaultElements() < size() && max < 0.0) {
return -1;
}
return result;
}
{code}
> Solve performance issues with Vector Implementations
> ----------------------------------------------------
>
> Key: MAHOUT-300
> URL: https://issues.apache.org/jira/browse/MAHOUT-300
> Project: Mahout
> Issue Type: Improvement
> Affects Versions: 0.3
> Reporter: Robin Anil
> Fix For: 0.3
>
> Attachments: MAHOUT-300.patch
>
>
> AbstractVector operations like times
> public Vector times(double x) {
> Vector result = clone();
> Iterator<Element> iter = iterateNonZero();
> while (iter.hasNext()) {
> Element element = iter.next();
> int index = element.index();
> result.setQuick(index, element.get() * x);
> }
> return result;
> }
> should be implemented as follows
> public Vector times(double x) {
> Vector result = clone();
> Iterator<Element> iter = result.iterateNonZero();
> while (iter.hasNext()) {
> Element element = iter.next();
> element.set(element.get() * x);
> }
> return result;
> }
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