apeforest commented on a change in pull request #14613: [MXNET-978] Higher
order gradient support for some unary operators
URL: https://github.com/apache/incubator-mxnet/pull/14613#discussion_r290914409
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File path: src/operator/tensor/elemwise_unary_op_trig.cc
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@@ -46,7 +46,33 @@ The storage type of ``sin`` output depends upon the input
storage type:
)code" ADD_FILELINE)
.set_attr<nnvm::FGradient>("FGradient", ElemwiseGradUseIn{ "_backward_sin" });
-MXNET_OPERATOR_REGISTER_BINARY_WITH_SPARSE_CPU_DR(_backward_sin,
unary_bwd<mshadow_op::sin_grad>);
+MXNET_OPERATOR_REGISTER_BINARY_WITH_SPARSE_CPU_DR(_backward_sin,
unary_bwd<mshadow_op::sin_grad>)
+.set_attr<nnvm::FGradient>("FGradient",
+ [](const nnvm::NodePtr& n, const std::vector<nnvm::NodeEntry>& ograds) {
+ // ograds[0]: d^2L/dx^2
+ // inputs[0]: dL/dy
+ // inputs[1]: x (ElemwiseUseIn)
+ // f(x) = sin(x)
+ // f'(x) = cos(x)
+ // f''(x) = -sin(x)
+ auto x_grad = MakeNode("cos", n->attrs.name + "_x_grad",
+ {n->inputs[1]}, nullptr, &n);
+ auto x_grad_grad = MakeNode("negative", n->attrs.name + "_x_grad_grad",
Review comment:
I renamed it. Also this indicates the gradient is on top of previous
gradient. User can still apply this recursively for nth order gradient.
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