[jira] Commented: (MAHOUT-489) SequentialAccessSparseVector iterators skip items

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

    [ https://issues.apache.org/jira/browse/MAHOUT-489?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12914477#action_12914477 ] 

Sean Owen commented on MAHOUT-489:
----------------------------------

Lots of action here.

1. There is indeed a problem with AllIterator being off-by-one at the end. I fixed that.
2. The non-zero iterator test in the patch has a slight problem, in that it sets a value to 0 but then expects the non-zero iterator to return it. I adjusted that along with a few other small points in the test.
3. Along the way I uncovered two smallish but probably important other problems: 
  - modifying an element via the all-elements iterator didn't clear the cached length squared. Hooray for unit tests; I knew this would continue to be a gotcha though...
  - iterating over an empty vector would cause an exception :(

Commit forthcoming.

> SequentialAccessSparseVector iterators skip items
> -------------------------------------------------
>
>                 Key: MAHOUT-489
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-489
>             Project: Mahout
>          Issue Type: Bug
>          Components: Math
>            Reporter: Laszlo Dosa
>            Assignee: Sean Owen
>             Fix For: 0.4
>
>         Attachments: MAHOUT-489.patch, MAHOUT-489.patch
>
>
> The following test cases fail, which iterates through the elements of the SequentialAccessSparseVector, because not every value is given back.
> SequentialAccessSparseVector.iterator() skips the last element, while the SequentialAccessSparseVector.iterateNonZero() skips the first element.
> int [] index = new int[] { 0, 1, 2, 3, 4, 5 };
> int [] values = new int[] { 0, 1, 2, 3, 4, 5 };
> SequentialAccessSparseVector vector;
> @Before
> public void setUp() {
> 	vector = new SequentialAccessSparseVector(6);
> 	for(int i = 0; i < Math.min(index.length, values.length); i++ ) {
> 		vector.set(index[i], values[i]);
> 	}
> }
> @Test
> public void testIteratorAll() {
> 	int elements = 0;
> 	Iterator<Element> it = vector.iterator();
> 	while (it.hasNext()) {
> 		System.out.println(it.next().get());
> 		elements++;
> 	}
> 	assertEquals((int)vector.get(Math.min(index.length,values.length)-1),values[Math.min(index.length, values.length)-1]);
> 	assertEquals(Math.min(index.length, values.length),elements);
> }
> @Test
> public void testIteratorNonNull() {
> 	int elements = 0;
> 	Iterator<Element> it = vector.iterateNonZero();
> 	while (it.hasNext()) {
> 		System.out.println(it.next().get());
> 		elements++;
> 	}
> 	assertEquals((int)vector.get(Math.min(index.length,values.length)-1),values[Math.min(index.length, values.length)-1]);
> 	assertEquals(Math.min(index.length,values.length),elements);  
> }

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