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https://issues.apache.org/jira/browse/MAHOUT-300?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12836624#action_12836624
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Robin Anil commented on MAHOUT-300:
-----------------------------------
I think the irregularity is due to the sparse vector generation process where
duplicate index values could get generated leaving some vectors much sparser
than the sparsity value
{code}
Vector v = new SequentialAccessSparseVector(cardinality, sparsity); //
sparsity!
int[] indexes = new int[sparsity];
double[] values = new double[sparsity];
for (int j = 0; j < sparsity; j++) {
double value = r.nextGaussian();
int index = sparsity < cardinality ? r.nextInt(cardinality) : j;
v.set(index, value);
indexes[j] = index;
values[j] = value;
}
{code}
instead i suggest this
{code}
Vector v = new SequentialAccessSparseVector(cardinality, sparsity); //
sparsity!
boolean[] featureSpace = new boolean[cardinality];
int[] indexes = new int[sparsity];
double[] values = new double[sparsity];
int j = 0;
while(j < sparsity) {
double value = r.nextGaussian();
int index = r.nextInt(cardinality);
if(featureSpace[index] == false) {
featureSpace[index] = true;
indexes[j] = index;
values[j++] = value;
v.set(index, value);
}
}
{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, MAHOUT-300.patch, MAHOUT-300.patch,
> MAHOUT-300.patch, MAHOUT-300.patch, 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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