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@ -31,88 +31,74 @@ static bool AllInSet(const std::vector<std::string>& names,
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return true;
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}
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static std::vector<size_t> InSetIdx(
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const std::vector<std::string>& names, const std::string& suffix,
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const std::unordered_set<std::string>& set) {
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std::vector<size_t> ret_val;
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ret_val.reserve(names.size());
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for (size_t i = 0; i < names.size(); ++i) {
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if (set.find(names[i] + suffix) != set.end()) {
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ret_val.push_back(i);
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}
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}
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return ret_val;
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}
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static std::shared_ptr<OperatorBase> EmptyOp() {
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static std::shared_ptr<OperatorBase> NOP() {
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auto net_op = std::make_shared<NetOp>();
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net_op->type_ = "@EMPTY_OP@";
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net_op->type_ = "@NOP@";
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net_op->CompleteAddOp();
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return net_op;
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}
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/**
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* @brief Backward an operator, implementation
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* @param forwardOp the forward operator
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* @param no_grad_names variable names not calculate for gradient. Like X@GRAD
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* is not needed.
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* @param uniq_id a unique index used inside BackwardImpl, it will be shared
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* through recursive invoke.
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* @return The backward operator. For simple situation, it is a simple operator.
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* For complex situation, it is a NetOp.
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*
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* See Backward.h for details
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*/
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static std::shared_ptr<OperatorBase> BackwardImpl(
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// Get backward operator from a forward operator, recursively implementation.
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//
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// no_grad_names the gradient variable names without gradient calculating.
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//
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// uniq_id is a unique index used inside recursively calling BackwardRecursive.
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// use `uid = uniq_id++;` to get the unique index, and pass `uniq_id` through
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// recursive calling.
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//
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// returns The backward operator. For simple situation, it is a simple
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// operator. For complex situation, it is a NetOp.
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//
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// See Backward.h for details
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static std::shared_ptr<OperatorBase> BackwardRecursive(
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const OperatorBase& forwardOp,
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std::unordered_set<std::string>& no_grad_names, size_t& uniq_id);
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std::shared_ptr<OperatorBase> BackwardRecursive(
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const OperatorBase& forwardOp,
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std::unordered_set<std::string>& no_grad_names, size_t& uniq_id) {
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/**
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* If all input gradients of forwarding operator do not need to calculate,
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* just return an EmptyOp. Not return null ptr because EmptyOp does not take
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* too much time for calculation, but it is useful for simplifying logic.
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*/
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// If all input gradients of forwarding operator do not need to calculate,
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// just return an NOP. Not return null ptr because NOP does not take
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// too much time for calculation, but it is useful for simplifying logic.
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if (AllInSet(forwardOp.inputs_, OperatorBase::GRAD_VAR_SUFFIX(),
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no_grad_names)) {
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return EmptyOp();
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return NOP();
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}
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/**
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* All output gradients of forwarding operator do not need to calculate. Then
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* all input gradients cannot be computed at all, and we put them into
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* `no_grad_names` set. Return an EmptyOp.
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*/
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// All output gradients of forwarding operator do not need to calculate. Then
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// all input gradients cannot be computed at all, and we put them into
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// `no_grad_names` set. Return an NOP.
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if (AllInSet(forwardOp.outputs_, OperatorBase::GRAD_VAR_SUFFIX(),
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no_grad_names)) {
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for (auto& name : forwardOp.inputs_) {
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/// Mark all input is not need
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// Mark all input is not need
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no_grad_names.insert(name + OperatorBase::GRAD_VAR_SUFFIX());
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}
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return EmptyOp();
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return NOP();
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}
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//! Returned gradient network
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// Returned gradient network
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auto net = std::make_shared<NetOp>();
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if (forwardOp.IsNetOp()) {
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/// Because forwardOp is a net op, it can static_cast.
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// Because forwardOp is a net op, it can static_cast.
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auto& forwardNet = static_cast<const NetOp&>(forwardOp);
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//! Map from output gradient variable name to operator's indices in backward
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//! net. That operator generates that variable.
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// Map from output gradient variable name to operator's indices in backward
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// net. That operator generates that variable.
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std::unordered_map<std::string, std::vector<size_t>> dup_output_ops;
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size_t local_op_id = 0;
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/// reversely travel forwardNet
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// reversely travel forwardNet
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for (auto it = forwardNet.ops_.rbegin(); it != forwardNet.ops_.rend();
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++it, ++local_op_id) {
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auto fwd = *it;
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auto bwd = BackwardImpl(*fwd, no_grad_names, uniq_id);
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auto bwd = BackwardRecursive(*fwd, no_grad_names, uniq_id);
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net->AddOp(bwd);
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for (auto& out : bwd->outputs_) {
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dup_output_ops[out].emplace_back(local_op_id);
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}
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}
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/// Get unique ID for this method.
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// Get unique ID for this method.
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auto uid = uniq_id++;
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// TODO(dzh): more comment
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using Pos = std::pair<size_t, std::shared_ptr<OperatorBase>>;
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@ -145,13 +131,15 @@ static std::shared_ptr<OperatorBase> BackwardImpl(
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}
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} else {
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//! TODO(fjy)
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std::shared_ptr<OperatorBase> grad_op = OpRegistry::CreateGradOp(forwardOp);
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for (std::string& grad_input : grad_op->inputs_) {
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if (no_grad_names.count(grad_input)) {
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std::string prefix = grad_input.substr(
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0, grad_input.size() - OperatorBase::GRAD_VAR_SUFFIX().size());
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grad_input = prefix + OperatorBase::ZERO_VAR_SUFFIX();
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// If part of input gradient of that operator is not calculated, fill
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// zero variables to that input gradient.
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net->AddOp(OpRegistry::CreateOp("fill_zeros_like", {prefix},
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{grad_input}, {}));
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}
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@ -173,8 +161,8 @@ static std::shared_ptr<OperatorBase> BackwardImpl(
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return net;
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}
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//! See header for comments
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extern std::shared_ptr<OperatorBase> Backward(
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// See header for comments
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std::shared_ptr<OperatorBase> Backward(
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const OperatorBase& forwardOp,
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const std::unordered_set<std::string>& no_grad_vars) {
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std::unordered_set<std::string> no_grad_names;
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@ -184,7 +172,7 @@ extern std::shared_ptr<OperatorBase> Backward(
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no_grad_names.insert(name + OperatorBase::GRAD_VAR_SUFFIX());
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}
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size_t uid = 0;
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return BackwardImpl(forwardOp, no_grad_names, uid);
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return BackwardRecursive(forwardOp, no_grad_names, uid);
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}
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} // namespace framework
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} // namespace paddle
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