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[SPARK-11084][ML][PYTHON] Check if index can contain non-zero value before binary search #9098

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[SPARK-11084][ML][PYTHON] Check if index can contain non-zero value before binary search #9098

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4 changes: 2 additions & 2 deletions python/pyspark/mllib/linalg/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -769,10 +769,10 @@ def __getitem__(self, index):
if index >= self.size or index < 0:
raise ValueError("Index %d out of bounds." % index)

insert_index = np.searchsorted(inds, index)
if insert_index >= inds.size:
if (inds.size == 0) or (index > inds.item(-1)):
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@jkbradley jkbradley Oct 14, 2015

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Curious: Is inds.item(-1) faster than inds[-1]? I wasn't sure.

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@zero323 zero323 Oct 14, 2015

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By itself it is slower than using __getitem__ but it returns standard Python scalar and overall it should be marginally faster when index is a standard scalar as well.

If you think that inds[-1] is better it shouldn't really matter. With crude tests I get ~40 ns difference on average (245 ns for [] and, 205 ns for inds)

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@jkbradley jkbradley Oct 16, 2015

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Sounds good, I'd keep what you have.

return 0.

insert_index = np.searchsorted(inds, index)
row_ind = inds[insert_index]
if row_ind == index:
return vals[insert_index]
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10 changes: 10 additions & 0 deletions python/pyspark/mllib/tests.py
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Expand Up @@ -252,6 +252,16 @@ def test_sparse_vector_indexing(self):
for ind in [7.8, '1']:
self.assertRaises(TypeError, sv.__getitem__, ind)

zeros = SparseVector(4, {})
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@jkbradley jkbradley Oct 14, 2015

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Isn't this already covered in the previous part of this test with "sv"?

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@zero323 zero323 Oct 14, 2015

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Well, It should be. I played with different implementations and I just wanted to be sure I didn't break anything. I can remove this if you want.

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@jkbradley jkbradley Oct 16, 2015

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It's OK for now; it's a quick test

self.assertEqual(zeros[0], 0.0)
self.assertEqual(zeros[3], 0.0)
for ind in [4, -5]:
self.assertRaises(ValueError, zeros.__getitem__, ind)

empty = SparseVector(0, {})
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@jkbradley jkbradley Oct 14, 2015

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This seems like a good test to have.

for ind in [-1, 0, 1]:
self.assertRaises(ValueError, empty.__getitem__, ind)

def test_matrix_indexing(self):
mat = DenseMatrix(3, 2, [0, 1, 4, 6, 8, 10])
expected = [[0, 6], [1, 8], [4, 10]]
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