EVOLUTION-MANAGER

Edit File: encapsulate_util.h

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// This file contains some utility functions for encapsulating XLA computation
// in host graph and encapsulating outside compilation in XLA computation.

#ifndef TENSORFLOW_COMPILER_JIT_ENCAPSULATE_UTIL_H_
#define TENSORFLOW_COMPILER_JIT_ENCAPSULATE_UTIL_H_

#include "absl/container/flat_hash_map.h"
#include "tensorflow/core/graph/graph.h"
#include "tensorflow/stream_executor/lib/statusor.h"

namespace tensorflow {

// Attribute marking output tensor shapes inferred by XLA. Attribute value is
// a list of PartialTensorShape objects.
extern const char kXlaInferredShapesAttrName[];

// Infers output shapes for all nodes in graph `g`. The output shapes will be
// stored in node attribute `kXlaInferredShapesAttrName`.
//
// We have to perform shape inference before encapsulation because after
// encapsulation, some nodes will be encapsulated into function call, and shape
// inference does not handle function call at the moment.
Status PerformStaticShapeInferenceBeforeEncapsulation(Graph* g);

// Attribute indicating that some ops in this node's XLA computation has control
// dependency on this node. Attribute value will always be "true".
extern const char kXlaConnectedToXlaComputationAttrName[];

// Attribute indicating that this node has control dependency on some ops in
// this node's XLA computation. Attribute value will always be "true".
extern const char kXlaConnectedFromXlaComputationAttrName[];

// Attribute indicating that this is an Placeholder node added to act as a
// temporary input node for an outside compilation node. Attribute value will be
// string (original input node name).
extern const char kOutsideCompilationOriginalNodeAttrName[];

// Attribute indicating that this is an Placeholder node added to act as a
// temporary input node for an outside compilation node. Attribute value will be
// int (src_output for original edge).
extern const char kOutsideCompilationSrcOutputAttrName[];

// Attribute indicating that this node has control dependencies on some other
// nodes within the same XLA cluster. Attribute value will be a list of string
// (node names).
extern const char kXlaControlDependenciesWithinXlaClusterAttrName[];

// Attribute indicating that this node is an outside compilation node which is
// lifted out of If/While/function node. Attribute value will always be boolean
// value "true".
extern const char kXlaIsLiftedArgAttrName[];

// Attribute indicating that this node is a Placeholder node for an _Arg node
// lifted out of If/While/function node. Attribute value will be a string, which
// is the outside compilation cluster name sending the lifted arg node to host.
extern const char kXlaLiftedArgOutsideCompilationAttrName[];

// Attribute indicating that this is an IdentityN node receiving inputs for a
// outside compilation Placeholder node (the original outside compilation node
// is moved out of TPU computation, and we left a Placeholder node there).
// Attribute value will be a string, which is the outside compilation cluster
// name for the outside compilation Placeholder node.
extern const char kXlaOutsideCompilationInputsAttrName[];

// Attribute indicating that this is a Placeholder node for an _Arg node used in
// outside compilation. We should not move this node out of XLA computation.
// Attribute value will always be boolean value "true".
extern const char kXlaIsPlaceholderForArg[];

// Information for XLA computation.
struct XlaClusterInfo {
  // Add an explicitly-defined default constructor for this class.
  //
  // The compiler may delete the default constructor here because
  // host_compute_core is a const member whose type (std::map) doesn't
  // necessarily have a user provided constructor -- while libc++ and
  // libstdc++ 4.8 provide a user defined default constructor, libstdc++ at
  // least >= 7.3 does not. See also c++11 [class.ctor] p5.
  //
  // TODO(klimek): In c++17 we'll be able to initialize host_compute_core
  // without losing aggregate initialization, which allows us to get rid of
  // the constructor definitions again.
  XlaClusterInfo() {}
  XlaClusterInfo(const string& cluster_name,
                 const NameAttrList& func_name_attrs, Node* node,
                 const std::map<string, int>& host_compute_core)
      : cluster_name(cluster_name),
        func_name_attrs(func_name_attrs),
        node(node),
        host_compute_core(host_compute_core) {}
  // XLA cluster name. It might be different from `func_name`.
  const string cluster_name;
  // Name and attributes of XLA computation function.
  const NameAttrList func_name_attrs;
  // The XLA computation node in the graph.
  Node* node;
  // A mapping from outside compilation cluster name to its device assignment.
  const std::map<string, int> host_compute_core;
};

// Finds dependencies between outside compilation clusters, including both data
// dependencies and control dependencies. cluster_deps maps the name name of an
// outside compilation cluster to a set of names of outside compilation clusters
// that it depends on.
stream_executor::port::StatusOr<
    std::unique_ptr<absl::flat_hash_map<string, std::vector<string>>>>
OutsideCompilationClusterDependencies(
    const Graph* g, const string& outside_compilation_attr_name);

// Preprocesses edges within the same XLA cluster. It will perform the following
// operations in order:
//
// 0.  Remove edges from source node to outside compilation nodes, and edges
//     from outside compilation nodes to sink node.
// 1a. For edges between different outside compilation clusters, remove the edge
//     and add attr "kXlaControlDependenciesWithinXlaClusterAttrName = src node
//     name" to dst node.
// 1b. For control edges between outside compilation and its XLA computation,
//     add attr "kXlaConnected{From, To}XlaComputationAttrName = true" to the
//     outside compilation node.
// 2.  For data edges between different outside compilations, remove the edge
//     and create a Placeholder node as dst node's input.
Status PreprocessEdgesBetweenOutsideCompilations(
    Graph* g, const string& outside_compilation_attr_name);

// Postprocesses edges within the same XLA cluster. This function reverts what
// `PreprocessEdgesBetweenOutsideCompilations` did. It will perform the
// following operations in order:
//
// 1. Remove Placeholder nodes between different outside compilations (created
//    in `PreprocessEdgesBetweenOutsideCompilations` step 2).
// 2a. Reconnect control edges between different outside compilations (marked by
//     `PreprocessEdgesBetweenOutsideCompilations` step 1a).
// Notice that control edges marked by
// `PreprocessEdgesBetweenOutsideCompilations` step 1b are not handled here.
// They are handled in `RewriteOutsideCompilationSubgraphFn`.
Status PostprocessEdgesBetweenOutsideCompilations(
    Graph* g, const string& outside_compilation_attr_name);
}  // namespace tensorflow

#endif  // TENSORFLOW_COMPILER_JIT_ENCAPSULATE_UTIL_H_