[API] Add linalg.svdvals

python/mxnet/numpy/linalg.py

@@ -24,7 +24,7 @@
 
 __all__ = ['norm', 'svd', 'cholesky', 'qr', 'inv', 'det', 'slogdet', 'solve', 'tensorinv', 'tensorsolve',
            'pinv', 'eigvals', 'eig', 'eigvalsh', 'eigh', 'lstsq', 'matrix_rank', 'cross', 'diagonal', 'outer',
-           'tensordot', 'trace', 'matrix_transpose', 'vecdot']
+           'tensordot', 'trace', 'matrix_transpose', 'vecdot', 'svdvals']
 __all__ += fallback_linalg.__all__
 
 
@@ -703,6 +703,31 @@ def svd(a):
     return _mx_nd_np.linalg.svd(a)
 
 
+def svdvals(a):
+    r"""
+    Computes the singular values of a matrix (or a stack of matrices) `x`.
+
+    Parameters
+    ----------
+    a : (..., M, N) ndarray
+        A real array with ``a.ndim >= 2`` and ``M <= N``.
+
+    Returns
+    -------
+    out : (..., M) ndarray
+        Vector(s) with the singular values, within each vector sorted in
+        descending order. The first ``a.ndim - 2`` dimensions have the same
+        size as those of the input `a`.
+
+    .. note::
+       `svdvals` is a standard api in
+       https://data-apis.org/array-api/latest/extensions/linear_algebra_functions.html#linalg-svdvals-x
+       instead of an official NumPy operator.
+    """
+    _, s, _ = _mx_nd_np.linalg.svd(a)
+    return s
+
+
 def cholesky(a):
     r"""
     Cholesky decomposition.

tests/python/unittest/test_numpy_op.py

@@ -5928,6 +5928,51 @@ def check_svd(UT, L, V, data_np):
     check_svd(UT, L, V, data_np)
 
 
+@use_np
+@pytest.mark.parametrize('shape', [
+    (3, 3),
+    (3, 5),
+    (4, 4),
+    (4, 5),
+    (5, 5),
+    (5, 6),
+    (6, 6),
+    (0, 1),
+    (6, 5, 6),
+    (2, 3, 3, 4),
+    (4, 2, 1, 2),
+    (0, 5, 3, 3),
+    (5, 0, 3, 3),
+    (3, 3, 0, 0),
+])
+@pytest.mark.parametrize('dtype', ['float32', 'float64'])
+@pytest.mark.parametrize('hybridize', [False, True])
+def test_np_linalg_svdvals(shape, dtype, hybridize):
+    class TestSVD(HybridBlock):
+        def __init__(self):
+            super(TestSVD, self).__init__()
+
+        def forward(self, data):
+            return np.linalg.svdvals(data)
+
+    rtol = atol = 0.01
+    test_svd = TestSVD()
+    if hybridize:
+        test_svd.hybridize()
+    data_np = onp.random.uniform(-10.0, 10.0, shape)
+    data_np = onp.array(data_np, dtype=dtype)
+    data = np.array(data_np, dtype=dtype)
+    if effective_dtype(data) == onp.dtype(np.float16):
+        pytest.skip()
+    mx_out = test_svd(data)
+    np_out = onp.linalg.svd(data, compute_uv=False)
+    # check svdvals validity
+    assert_almost_equal(mx_out.asnumpy(), np_out, rtol=rtol, atol=atol)
+    # Test imperative once again
+    mx_out = np.linalg.svdvals(data)
+    assert_almost_equal(mx_out.asnumpy(), np_out, rtol=rtol, atol=atol)
+
+
 @use_np
 def test_np_linalg_qr():
     class TestQR(HybridBlock):