anirudhacharya commented on a change in pull request #11209: [MXNET-536]
implement var/std operators
URL: https://github.com/apache/incubator-mxnet/pull/11209#discussion_r224232619
##########
File path: tests/python/unittest/test_operator.py
##########
@@ -5702,6 +5702,98 @@ def test_softmax():
check_softmax_grad(default_context())
check_smoothed_softmax_grad(default_context())
+@with_seed()
+def test_variance():
+ def true_var(x, axis=None):
+ if len(x.shape) == 1:
+ return np.var(x, keepdims=True, axis=axis)
+ else:
+ return np.var(x, axis=axis)
+ def true_var_grad(x, ograd, axis=None):
+ if axis is None:
+ return 2 * (x - np.mean(x)) * ograd / np.prod(x.shape)
+ else:
+ denom = x.shape[axis]
+ ograd_shape = tuple(1 if i == axis else k for i, k in enumerate(x.shape))
+ return 2 * (x - np.mean(x, axis=axis, keepdims=True)) *
ograd.reshape(ograd_shape) / denom
+
+ for ndim in range(1, 6):
+ # check forward
+ shape = rand_shape_nd(ndim, 5)
+ data = rand_ndarray(shape=shape, stype='default')
+ data_np = data.asnumpy()
+ expected = true_var(data_np)
+ output = mx.nd.variance(data)
+ assert_almost_equal(output.asnumpy(), expected)
+ for axis in range(ndim):
+ expected = true_var(data_np, axis=axis)
+ output = mx.nd.variance(data, axis=axis)
Review comment:
if it is piggy-backing on ReduceAxesOp, then it should be able support tuple
values for axes I think. Because the `sum` operator does do it -
http://mxnet.incubator.apache.org/api/python/symbol/symbol.html#mxnet.symbol.sum
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