text: #pragma once
  
  #include <torch/csrc/jit/ir/ir.h>
  
  #include <unordered_map>
  #include <vector>
  
  namespace torch {
  namespace jit {
  
  /**
   * \brief A structure describing a match of a pattern in a graph.
   *
   * The structure contains an anchor node, from which the match was found, and
   * match-maps for nodes and values. A match-map specifies the correspondance
   * between nodes in the pattern graph (match-map keys) with nodes in the actual
   * graph (match-map values). We keep such maps for both nodes and values.
   */
  struct Match {
    Node* anchor;
    std::unordered_map<const Node*, Node*> nodes_map;
    std::unordered_map<const Value*, Value*> values_map;
  };
  
  /**
   * \brief Find all matches of a \p PATTERN in a \p GRAPH.
   *
   * The function returns a vector of match-descriptors (see description of
   * `struct Match`).
   *
   * Matching rules:
   *  - Pattern graph must contain a single block.
   *  - Matched subgraphs do not span across different blocks.
   *  - No uses outside the match are allowed, except for Param and Return nodes.
   *  Basically, we're matching hammocks, not arbitrary subgraphs.
   *  - The pattern graph must return only one value (i.e. it must have a single
   *  node leading to return).
   *  - Nodes that are not used in computation of the return value in the pattern
   * graph are ignored during matching (IOW, we're essentially performing DCE on
   * the pattern).
   *  - Pattern graph nodes cannot alias. TODO: the check not implemented yet.
   *  - Aliasing nodes in the graph cannot consitute a match (i.e. through all
   * found matches, no nodes in the subgraph alias with each other). TODO: check
   * not implemented yet.
   *  - The matcher will not mutate either the pattern graph or the matched graph.
   * The matched graph is taken as non-const so that Match may contain non-const
   * pointers.  This enables clients of this API to use Match to drive mutations.
   *
   * Note [Multi-output Patterns]
   * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   * Subgraph matcher provides limited support for multi-output patterns. With a
   * single output pattern, a single scan through the graph is sufficient to
   * find all the matches: given a starting node (an "anchor"), we can
   * deterministically check whether a pattern matches a subgraph corresponding to
   * this anchor node. For a general case of multi-output patterns, we would have
   * N anchors, which would result in M^N comparisons (M is the size of the
   * graph). Clearly this is computationally prohibitive.
   *
   * To overcome this, we impose some constraints on the multi-output patterns
   * that we accept. We require that checking whether the pattern matches a
   * subgraph would still be fully determined by a single node in the graph. To
   * achieve this, we designate the first output in the pattern as the "main"
   * output and assume that we can traverse up from this node to match the
   * entire pattern.
   *
   * Corrolary 1: the order of outputs in the pattern matters!
   * Corollary 2: patterns cannot contain any nodes not participating in the main
   * output computation.
   */
  std::vector<Match> TORCH_API
  findPatternMatches(const Graph& pattern, Graph& graph);
  
  } // namespace jit
  } // namespace torch
  