Function SigmoidGrad

tensorflow/cc/gradients/math_grad.cc:267–280

REGISTER_GRADIENT_OP("Atan2", Atan2Grad);

Status SigmoidGrad(const Scope& scope, const Operation& op,
                   const std::vector<Output>& grad_inputs,
                   std::vector<Output>* grad_outputs) {
  // Use the built-in operator.
  // Note that the built-in operator does not return the conjugate of
  // the gradient.
  auto grad = grad_inputs[0];
  // Optimization to avoid calculating conj(y) until the gradient is
  // evaluated.
  Scope grad_scope = scope.WithControlDependencies(grad);
  auto y = ConjugateHelper(grad_scope, op.output(0));
  grad_outputs->push_back(internal::SigmoidGrad(grad_scope, y, grad));
  return grad_scope.status();
}
REGISTER_GRADIENT_OP("Sigmoid", SigmoidGrad);

Status SignGrad(const Scope& scope, const Operation& op,