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Fix returning scalar input in Python autograd function #7934

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Merged
soumith merged 2 commits into from
May 30, 2018
Merged

Fix returning scalar input in Python autograd function #7934

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5d3ed93
fix _wrap_outputs not working with scalar inputs
ssnl May 29, 2018
b68ffd9
add a test
ssnl May 29, 2018
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15 changes: 8 additions & 7 deletions test/test_autograd.py
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Original file line number Diff line number Diff line change
Expand Up @@ -150,13 +150,14 @@ def forward(ctx, x):
def backward(ctx, grad):
return grad * 2

v = torch.ones(1, requires_grad=True)
MyFunction.apply(v).backward()
self.assertEqual(v.grad.data.tolist(), [2])

v.grad.data.zero_()
MyFunction.apply(v.clone()).backward()
self.assertEqual(v.grad.data.tolist(), [2])
for shape in [(1,), ()]:
v = torch.ones(shape, requires_grad=True)
MyFunction.apply(v).backward()
self.assertEqual(v.grad, torch.full(shape, 2))

v.grad.data.zero_()
MyFunction.apply(v.clone()).backward()
self.assertEqual(v.grad, torch.full(shape, 2))

def test_legacy_function_none_grad(self):
class MyFunction(Function):
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4 changes: 2 additions & 2 deletions torch/csrc/autograd/python_function.cpp
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Expand Up @@ -407,7 +407,7 @@ static void _wrap_outputs(THPFunction *self,
} else if (is_input) {
// An input has been returned, but it wasn't modified. Return it as a view
// so that we can attach a new grad_fn to the Variable.
var = var.slice();
var = var.view_as(var);

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var.set_gradient_edge({cdata, output_nr});
} else if (cdata) {
var.set_gradient_edge({cdata, output_nr});
Expand Down Expand Up @@ -602,7 +602,7 @@ static void _trace_post_record(

auto state_lock = trace_info.state->lock();
trace_info.n->i_(attr::inplace, is_inplace);

}

PyObject* process_outputs(PyObject *op_obj, THPFunction* grad_fn, const UnpackedInput& unpacked,
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