experiments/STT-tensorflow
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Unreachable input gradients (#13071)

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* Check if inputs are reachable from outputs in AddSymbolicGradients.

* Removing LOG.

* Edit following the PR comments.

* Lines > 80 chars.

* Formatting comments in gradients_test.

* Eliminate m2 and renamed m1->m, dm1->diff_m

* Edit InvalidArgument string concatenation.
This commit is contained in:
Courtial Florian 2017-09-18 19:35:47 +02:00 committed by Shanqing Cai
parent 66eed36466
commit a0bbeb10e2
2 changed files with 40 additions and 13 deletions
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10
tensorflow/cc/framework/gradients.cc
View File

@ -175,8 +175,14 @@ Status SymbolicGradientBuilder::Initialize() {
"Must specify a gradient input for each output.");
}
std::vector<bool> reachable_nodes = GetReachableNodes();
// TODO(theflofly) Check that inputs_ are reachable from
// outputs_ using reachable_nodes
for (const Output& input : inputs_) {
if (!reachable_nodes[input.node()->id()]) {
return errors::InvalidArgument(
"Cannot compute the partial derivative for node '",
input.node()->name(),
"' as it's unreachable from the output node(s).");
}
}
grad_outputs_->clear();
grad_outputs_->resize(inputs_.size());
// Populate `output_nodes_` from node ids in `outputs_`.

43
tensorflow/cc/framework/gradients_test.cc
View File

@ -48,9 +48,9 @@ class GradientsTest : public ::testing::Test {
Scope scope_test_;
};
// EX.
// Example:
// ^ ^
// dy| dx| // MatMul Gradient Graph
// dy| dx| (MatMul Gradient Graph)
// | |
// MatMul_1 MatMul_2
// ^ ^ ^ ^
@ -61,7 +61,7 @@ class GradientsTest : public ::testing::Test {
// | Const_3 |
// | |
// | ^ |
// | z| | // MatMul Forward Graph
// | z| | (MatMul Forward Graph)
// | | |
// | MatMul_0 |
// | / \ |
@ -373,24 +373,22 @@ TEST_F(GradientsTest, UnreachableEdgeGradOneOutput) {
auto y_const = Const(scope_test_, {{1.0}, {2.0}, {3.0}});
auto y_assign = Assign(scope_test_, y, y_const);
auto m1 = MatMul(scope_test_, x, y);
auto m = MatMul(scope_test_, x, y);
auto z = Variable(scope_test_, {1, 3}, DT_DOUBLE);
auto z_const = Const(scope_test_, {{9.0, 10.0, 11.0}});
auto z_assign = Assign(scope_test_, z, z_const);
auto m2 = MatMul(scope_test_, y, z);
auto dm1 = Const(scope_test_, {{0.5}, {0.5}});
auto diff_m = Const(scope_test_, {{0.5}, {0.5}});
std::vector<Output> grad_outputs;
TF_ASSERT_OK(
AddSymbolicGradients(scope_test_, {m1}, {y}, {dm1}, &grad_outputs));
AddSymbolicGradients(scope_test_, {m}, {y}, {diff_m}, &grad_outputs));
std::vector<Tensor> outputs;
test::GetTensors(scope_test_, {x_assign, y_assign, z_assign},
{grad_outputs[0]}, &outputs);
// dz/dy = xT * dm1
// dz/dy = xT * diff_m
test::ExpectTensorNear<double>(
outputs[0], test::AsTensor<double>({2.5, 3.5, 4.5}, {3, 1}), 1e-5);
}
@ -424,13 +422,36 @@ TEST_F(GradientsTest, UnreachableEdgeGradTwoOutputs) {
test::GetTensors(scope_test_, {x_assign, y_assign, z_assign},
{grad_outputs[0]}, &outputs);
// the gradients from m1 and m2 will be summed to compute the gradient
// w.r.t y
// The gradients from m1 and m2 will be summed to compute the gradient
// w.r.t y:
// dz/dy = xT * dm1 + dm2 * zT
test::ExpectTensorNear<double>(
outputs[0], test::AsTensor<double>({17.5, 24.7, 26.8}, {3, 1}), 1e-5);
}
TEST_F(GradientsTest, UnreachableInput) {
auto x = Const(scope_test_, {{1.0, 2.0, 3.0}, {4.0, 5.0, 6.0}});
auto y = Const(scope_test_, {{1.0}, {2.0}, {3.0}});
auto z = Const(scope_test_.WithOpName("z"), {{9.0, 10.0, 11.0}});
auto m1 = MatMul(scope_test_, x, y);
auto m2 = MatMul(scope_test_, y, z);
auto dm1 = Const(scope_test_, {{0.5}, {0.5}});
// From m1, z is unreachable, so an error status should be returned.
// m2 m1
// | |
// * *
// / \ / \
// z y x
std::vector<Output> grad_outputs;
Status status = AddSymbolicGradients(scope_test_, {m1}, {z}, {dm1},
&grad_outputs);
EXPECT_EQ(status.code(), error::INVALID_ARGUMENT);
EXPECT_EQ(status.error_message(), "Cannot compute the partial derivative"
" for node 'z' as it's unreachable from the output node(s).");
}
// StopGradientSingleOutputMultiEdgeTest tests combinations of valid and
// 'NoGradient' (induced by StopGradient op) returned along multiple edges from
// a single nodes output.