#ifndef CAFFE2_OPERATORS_GRU_UNIT_OP_H_
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#define CAFFE2_OPERATORS_GRU_UNIT_OP_H_
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#include "caffe2/core/context.h"
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#include "caffe2/core/operator.h"
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#include "caffe2/utils/math.h"
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namespace caffe2 {
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namespace detail {
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template <typename T>
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inline T sigmoid(T x) {
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return 1.0f / (1.0f + exp(-x));
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}
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template <typename T>
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inline T host_tanh(T x) {
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return 2.0f * sigmoid(2.0f * x) - 1.0f;
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}
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template <typename T, typename Context>
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void GRUUnit(
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int N,
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int D,
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int t,
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const T* H_prev,
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const T* X,
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const int32_t* seqLengths,
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bool drop_states,
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T* H,
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Context* /*context*/) {
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for (int n = 0; n < N; ++n) {
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const bool valid = seqLengths == nullptr || t < seqLengths[n];
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for (int d = 0; d < D; ++d) {
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if (!valid) {
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if (drop_states) {
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H[d] = 0;
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} else {
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H[d] = H_prev[d];
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}
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} else {
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const T update = X[1 * D + d];
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const T output = X[2 * D + d];
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T sigmoid_update = sigmoid(update);
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H[d] = H_prev[d] * sigmoid_update +
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host_tanh(output) * (1.0f - sigmoid_update);
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}
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}
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H_prev += D;
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X += 3 * D;
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H += D;
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}
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}
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template <typename T, typename Context>
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void GRUUnitGradient(
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int N,
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int D,
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int t,
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const T* H_prev,
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const T* X,
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const int32_t* seqLengths,
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const T* H,
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const T* H_diff,
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bool drop_states,
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T* H_prev_diff,
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T* X_diff,
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Context* /*context*/) {
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for (int n = 0; n < N; ++n) {
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const bool valid = seqLengths == nullptr || t < seqLengths[n];
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for (int d = 0; d < D; ++d) {
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T* h_prev_diff = H_prev_diff + d;
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T* reset_diff = X_diff + 0 * D + d;
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T* update_diff = X_diff + 1 * D + d;
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T* output_diff = X_diff + 2 * D + d;
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if (!valid) {
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if (drop_states) {
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*h_prev_diff = 0;
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} else {
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*h_prev_diff = H_diff[d];
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}
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*reset_diff = 0;
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*update_diff = 0;
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*output_diff = 0;
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} else {
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// Calculate Gate Outputs
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const T u = sigmoid(X[1 * D + d]);
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const T o = host_tanh(X[2 * D + d]);
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*h_prev_diff = H_diff[d] * u;
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*reset_diff = 0; // 0 contribution to gradient from this operation
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*update_diff = (H_diff[d] * H_prev[d] - H_diff[d] * o) * u * (1.0f - u);
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*output_diff = H_diff[d] * (1.0f - u) * (1.0f - o * o);
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}
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}
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H_prev += D;
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X += 3 * D;
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H += D;
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H_diff += D;
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X_diff += 3 * D;
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H_prev_diff += D;
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}
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}
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} // namespace detail
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template <typename T, typename Context>
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class GRUUnitOp : public Operator<Context> {
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public:
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template <class... Args>
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explicit GRUUnitOp(Args&&... args)
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: Operator<Context>(std::forward<Args>(args)...),
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drop_states_(
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this->template GetSingleArgument<bool>("drop_states", false)),
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sequence_lengths_(
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this->template GetSingleArgument<bool>("sequence_lengths", true)) {}
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USE_OPERATOR_CONTEXT_FUNCTIONS;
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bool RunOnDevice() override {
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// handle potentially-missing sequence lengths input
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const size_t TIMESTEP = SEQ_LENGTHS + (sequence_lengths_ ? 1 : 0);
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// Extract N
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const auto N = Input(HIDDEN_T_M_1).size(1);
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// Gates: 1xNxG
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const auto G = Input(GATES).size(2);
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const auto D = Input(HIDDEN_T_M_1).size(2);
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CAFFE_ENFORCE_EQ(3 * D, G);
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const auto* H_prev = Input(HIDDEN_T_M_1).template data<T>();
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const auto* X = Input(GATES).template data<T>();
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const int32_t* seqLengths = nullptr;
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if (sequence_lengths_) {
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CAFFE_ENFORCE_EQ(Input(SEQ_LENGTHS).numel(), N);
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seqLengths = Input(SEQ_LENGTHS).template data<int32_t>();
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}
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const auto t = static_cast<OperatorBase*>(this)
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->Input<Tensor>(TIMESTEP, CPU)
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.template data<int32_t>()[0];
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Output(HIDDEN_T)->ResizeLike(Input(HIDDEN_T_M_1));
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auto* H = Output(HIDDEN_T)->template mutable_data<T>();
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detail::GRUUnit<T, Context>(
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N, D, t, H_prev, X, seqLengths, drop_states_, H, &context_);
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return true;
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}
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protected:
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INPUT_TAGS(HIDDEN_T_M_1, GATES, SEQ_LENGTHS);
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// additional input tags are determined dynamically based on whether
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// sequence_lengths is present.
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OUTPUT_TAGS(HIDDEN_T);
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private:
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bool drop_states_;
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bool sequence_lengths_;
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};
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template <typename T, typename Context>
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class GRUUnitGradientOp : public Operator<Context> {
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public:
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template <class... Args>
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explicit GRUUnitGradientOp(Args&&... args)
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: Operator<Context>(std::forward<Args>(args)...),
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drop_states_(
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this->template GetSingleArgument<bool>("drop_states", false)),
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sequence_lengths_(
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this->template GetSingleArgument<bool>("sequence_lengths", true)) {}
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USE_OPERATOR_CONTEXT_FUNCTIONS;
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bool RunOnDevice() override {
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// handle potentially-missing sequence lengths input
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const size_t inputOffset = SEQ_LENGTHS + (sequence_lengths_ ? 1 : 0);
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const size_t TIMESTEP = inputOffset;
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const size_t HIDDEN_T = inputOffset + 1;
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const size_t HIDDEN_T_GRAD = inputOffset + 2;
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// Extract N
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const auto N = Input(HIDDEN_T_M_1).size(1);
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// Gates: 1xNxG
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const auto G = Input(GATES).size(2);
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const auto D = Input(HIDDEN_T_M_1).size(2);
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CAFFE_ENFORCE_EQ(3 * D, G);
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const auto* H_prev = Input(HIDDEN_T_M_1).template data<T>();
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const auto* X = Input(GATES).template data<T>();
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const auto t = static_cast<OperatorBase*>(this)
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->Input<Tensor>(TIMESTEP, CPU)
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.template data<int32_t>()[0];
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const auto* H = Input(HIDDEN_T).template data<T>();
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const auto* H_diff = Input(HIDDEN_T_GRAD).template data<T>();
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const int32_t* seqLengths = nullptr;
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if (sequence_lengths_) {
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CAFFE_ENFORCE_EQ(Input(SEQ_LENGTHS).numel(), N);
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seqLengths = Input(SEQ_LENGTHS).template data<int32_t>();
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}
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Output(HIDDEN_T_M_1_GRAD)->ResizeLike(Input(HIDDEN_T_M_1));
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auto* H_prev_diff = Output(HIDDEN_T_M_1_GRAD)->template mutable_data<T>();
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Output(GATES_GRAD)->ResizeLike(Input(GATES));
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auto* X_diff = Output(GATES_GRAD)->template mutable_data<T>();
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detail::GRUUnitGradient<T, Context>(
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N,
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D,
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t,
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H_prev,
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X,
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seqLengths,
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H,
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H_diff,
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drop_states_,
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H_prev_diff,
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X_diff,
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&context_);
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return true;
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}
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protected:
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INPUT_TAGS(HIDDEN_T_M_1, GATES, SEQ_LENGTHS);
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OUTPUT_TAGS(HIDDEN_T_M_1_GRAD, GATES_GRAD);
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private:
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bool drop_states_;
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bool sequence_lengths_;
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};
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} // namespace caffe2
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#endif // CAFFE2_OPERATORS_GRU_UNIT_OP_H_
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