EVOLUTION-MANAGER

Edit File: while_loop.h

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==============================================================================*/

#ifndef TENSORFLOW_CC_OPS_WHILE_LOOP_H_
#define TENSORFLOW_CC_OPS_WHILE_LOOP_H_

#include <string>
#include <vector>

#include "tensorflow/cc/framework/ops.h"
#include "tensorflow/cc/framework/scope.h"

namespace tensorflow {
namespace ops {

// Function that takes cond graph inputs and returns cond graph boolean output.
// 'output' need not be set if an error is returned.
typedef std::function<Status(const Scope&, const std::vector<Output>& inputs,
                             Output* output)>
    CondGraphBuilderFn;

// Function that takes body graph inputs and returns body graph outputs.
// 'outputs' need not be populated if an error is returned.
typedef std::function<Status(const Scope&, const std::vector<Output>& inputs,
                             std::vector<Output>* outputs)>
    BodyGraphBuilderFn;

// Constructs a while loop.
//
// Arguments:
// * scope: used to construct the while loop.
// * inputs: the initial values of the loop variables. Must be non-empty.
// * cond: a function that builds the condition graph of the loop. Takes the
//     current loop variables as inputs and returns a scalar boolean Output
//     indicating whether the loop should continue.
// * body: a function that builds the body graph of the loop. Takes the current
//     loop variables as inputs and returns the updated loop variables.
// * frame_name: the frame name to use for this while loop. This should be a
//     unique name. This will be used as a prefix for created operations.
// * outputs: output param that returns final loop variable outputs in non-error
//     case. Must be non-null and empty.
// * create_while_ctx: if true, a WhileContext is created and populated for this
//     loop. See core/graph/while_context.h for more details on
//     WhileContexts. This is set to false for loops used as part of gradient
//     computations, since they're part of the gradient for a loop in the
//     forward-pass.
//     TODO(skyewm): revisit this. Should we create WhileContexts for all loops,
//     even if we don't need them?
// * cond_output: if non-null, the output of the predicate is returned. This
//     will always be a LoopCond node.
//
// Returns an error if the while loop could not be fully constructed.
//
// TODO(skyewm): clean up partially-constructed loop in error case
// TODO(skyewm): create public interface to this method
Status BuildWhileLoop(const Scope& scope, const std::vector<Output>& inputs,
                      const CondGraphBuilderFn& cond,
                      const BodyGraphBuilderFn& body, const string& frame_name,
                      OutputList* outputs, bool create_while_ctx = true,
                      Output* cond_output = nullptr);

}  // namespace ops
}  // namespace tensorflow

#endif  // TENSORFLOW_CC_OPS_WHILE_LOOP_H_