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Normalize negative axes in sort and argsort #4332

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Merged
zcbenz merged 2 commits into from
Aug 22, 2026
Merged

Normalize negative axes in sort and argsort #4332

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beac07f
Normalize negative axes in sort and argsort
deBrian07 Aug 18, 2026
75c6872
Merge branch 'main' into fix-sort-argsort-axis-normalization
deBrian07 Aug 21, 2026
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24 changes: 4 additions & 20 deletions mlx/ops.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2794,17 +2794,9 @@ array sort(const array& a, StreamOrDevice s /* = {} */) {

/** Returns a sorted copy of the array along a given axis. */
array sort(const array& a, int axis, StreamOrDevice s /* = {} */) {
// Check for valid axis
if (axis + static_cast<int>(a.ndim()) < 0 ||
axis >= static_cast<int>(a.ndim())) {
std::ostringstream msg;
msg << "[sort] Received invalid axis " << axis << " for array with "
<< a.ndim() << " dimensions.";
throw std::invalid_argument(msg.str());
}

auto ax = normalize_axis_index(axis, a.ndim(), "[sort] ");
return array(
a.shape(), a.dtype(), std::make_shared<Sort>(to_stream(s), axis), {a});
a.shape(), a.dtype(), std::make_shared<Sort>(to_stream(s), ax), {a});
}

/** Returns indices that sort the flattened array. */
Expand All @@ -2815,17 +2807,9 @@ array argsort(const array& a, StreamOrDevice s /* = {} */) {

/** Returns indices that sort the array along a given axis. */
array argsort(const array& a, int axis, StreamOrDevice s /* = {} */) {
// Check for valid axis
if (axis + static_cast<int>(a.ndim()) < 0 ||
axis >= static_cast<int>(a.ndim())) {
std::ostringstream msg;
msg << "[argsort] Received invalid axis " << axis << " for array with "
<< a.ndim() << " dimensions.";
throw std::invalid_argument(msg.str());
}

auto ax = normalize_axis_index(axis, a.ndim(), "[argsort] ");
return array(
a.shape(), uint32, std::make_shared<ArgSort>(to_stream(s), axis), {a});
a.shape(), uint32, std::make_shared<ArgSort>(to_stream(s), ax), {a});
}

/**
Expand Down
14 changes: 14 additions & 0 deletions python/tests/test_vmap.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1023,6 +1023,20 @@ def fn(x, y):
self.assertTrue(mx.array_equal(expected, out))
self.assertEqual(6, counter[0])

def test_vmap_sort(self):
a = mx.random.uniform(shape=(3, 5))
expected = mx.stack([mx.sort(a[:, i]) for i in range(a.shape[1])], axis=1)
for axis in (0, -1):
out = mx.vmap(lambda x: mx.sort(x, axis=axis), in_axes=1, out_axes=1)(a)
self.assertTrue(mx.array_equal(out, expected))

def test_vmap_argsort(self):
a = mx.random.uniform(shape=(3, 5))
expected = mx.stack([mx.argsort(a[:, i]) for i in range(a.shape[1])], axis=1)
for axis in (0, -1):
out = mx.vmap(lambda x: mx.argsort(x, axis=axis), in_axes=1, out_axes=1)(a)
self.assertTrue(mx.array_equal(out, expected))


if __name__ == "__main__":
mlx_tests.MLXTestRunner()