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https://issues.apache.org/jira/browse/MAHOUT-1091?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13472599#comment-13472599
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Ted Dunning commented on MAHOUT-1091:
-------------------------------------
For instance, this test:
{code}
public void testIterators() {
final T v0 = vectorToTest(20);
double sum = 0;
int elements = 0;
int nonZero = 0;
for (Vector.Element element : v0) {
elements++;
sum += element.get();
if (element.get() != 0) {
nonZero++;
}
}
int nonZeroIterated = 0;
final Iterator<Vector.Element> i = v0.iterateNonZero();
while (i.hasNext()) {
i.next();
nonZeroIterated++;
}
assertEquals(20, elements);
assertEquals(v0.size(), elements);
assertEquals(nonZeroIterated, nonZero);
assertEquals(v0.zSum(), sum, 0);
}
{code}
Note how the iteration test verifies that it sees all the elements, but sees
only the non-zeros in the non-zero iteration.
> Bug in SequentialAccessSparseVector full iteration
> --------------------------------------------------
>
> Key: MAHOUT-1091
> URL: https://issues.apache.org/jira/browse/MAHOUT-1091
> Project: Mahout
> Issue Type: Bug
> Components: Math
> Reporter: Ted Dunning
> Fix For: 0.8
>
> Attachments:
> 0001-MAHOUT-1091-Add-test-to-demonstrate-broken-iterator-.patch,
> 0001-MAHOUT-1091-Add-test-to-demonstrate-broken-iterator-.patch,
> MAHOUT-1091.patch
>
>
> The iterator for the SequentialAccessSparseVector doesn't return any items
> beyond the last non-zero. This breaks some stuff pretty massively, but
> hopefully doesn't break much user code since iterating through all elements
> of a sparse vector is a relatively rare thing to do.
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