mindspore2022/mindspore/ccsrc/utils/cse.cc

/**
 * This is the C++ adaptation and derivative work of Myia (https://github.com/mila-iqia/myia/).
 *
 * Copyright 2019-2022 Huawei Technologies Co., Ltd
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "include/common/utils/cse.h"

#include <vector>
#include <set>

#include "ir/anf.h"
#include "ir/scalar.h"
#include "utils/hash_map.h"
#include "abstract/abstract_function.h"
#include "utils/flags.h"
#include "include/common/utils/utils.h"
#include "utils/anf_utils.h"

namespace mindspore {
/* namespace to support opt */
namespace opt {
using mindspore::abstract::AbstractBase;
using mindspore::abstract::AbstractFunction;
using mindspore::abstract::AbstractFunctionPtr;

bool WithRecomputedScope(const AnfNodePtr &node) {
  MS_EXCEPTION_IF_NULL(node);
  if (!node->isa<CNode>()) {
    return false;
  }
  auto full_name_with_scope = node->fullname_with_scope();
  return full_name_with_scope.find(kAttrRecompute) == 0;
}

bool IsSetRecomputed(const CNodePtr &a, const CNodePtr &b) {
  return (WithRecomputedScope(a) && !a->HasAttr(kAttrNeedCseAfterRecompute)) ||
         (WithRecomputedScope(b) && !b->HasAttr(kAttrNeedCseAfterRecompute));
}

void UpdateDebugInfoAndDumpFlag(const AnfNodePtr &main, const AnfNodePtr &node) {
  if (main == nullptr || !main->isa<CNode>()) {
    return;
  }
  if (AnfUtils::GetDumpFlag(node) && !AnfUtils::GetDumpFlag(main)) {
    AnfUtils::SetDumpFlag(main);
  }
  auto main_cnode = main->cast<CNodePtr>();
  main_cnode->AddFusedDebugInfo(node);
}

BasePtr AbsOf(const AnfNodePtr &node, bool ignore_fg_abs_tracking_id) {
  MS_EXCEPTION_IF_NULL(node);
  auto node_abs = node->abstract();
  // In testcase: TestOptOpt.CSE, node->abstract() is null.
  if (node_abs == nullptr) {
    return kAnyValue;
  }
  if (node_abs->isa<abstract::PrimitiveAbstractClosure>()) {
    // Ignore the tracking_id and prim pointer hash.
    auto prim_abs = node_abs->cast<abstract::PrimitiveAbstractClosurePtr>();
    return prim_abs->prim();
  } else if (ignore_fg_abs_tracking_id && node_abs->isa<abstract::FuncGraphAbstractClosure>()) {
    // Ignore the tracking_id.
    auto new_fg_abs = node_abs->cast<abstract::AbstractFunctionPtr>()->Copy();
    new_fg_abs->set_tracking_id(nullptr);
    return new_fg_abs;
  }
  return node_abs;
}

// For a single function graph (fg), this function groups nodes based on their computed hash values 
// and then attempts to replace duplicate nodes within these groups.
// @param fg: The target function graph to process.
// @param manager: The manager for this function graph.
// @return: Whether the function graph was changed.
bool CSE::BuildOrderGroupAndDoReplaceForOneGraph(const FuncGraphPtr &fg, const FuncGraphManagerPtr &manager) const {
  MS_EXCEPTION_IF_NULL(fg);
  
  // Lists to store ordering of groups, groupings of nodes based on hash values, and hash values for each node.
  std::vector<std::size_t> order_group;
  mindspore::HashMap<std::size_t, std::vector<AnfNodePtr>> groups;
  mindspore::HashMap<AnfNodePtr, std::size_t> hashes;

  // Topologically sort the nodes in the function graph starting from the return node.
  std::vector<AnfNodePtr> toposet = TopoSort(fg->get_return());

  // Compute the hash value for each node and group nodes based on these values.
  for (auto node : toposet) {
    MS_EXCEPTION_IF_NULL(node);
    
    // Skip nodes that have already been hashed.
    if (hashes.find(node) != hashes.end()) {
      continue;
    }

    std::size_t h = 0;
    if (node->isa<ValueNode>()) {
      ValueNodePtr value_node = node->cast<ValueNodePtr>();
      auto value = value_node->value();
      MS_EXCEPTION_IF_NULL(value);
      // Combine the hash of the node's value with its abstract hash.
      h = hash_combine(value->hash(), (AbsOf(value_node, true)->hash()));
    } else if (node->isa<CNode>()) {
      auto cnode = node->cast<CNodePtr>();
      auto &inputs = cnode->inputs();
      size_t init = 0;
      // Combine the hash values of all inputs to the compute node.
      h = std::accumulate(inputs.begin(), inputs.end(), init, [&hashes](std::size_t hash, const AnfNodePtr &node_in) {
        return hash_combine(hash, hashes[node_in]);
      });
    } else if (node->isa<Parameter>()) {
      // For parameter nodes, use the node's hash.
      h = node->hash();
    } else {
      MS_LOG(ERROR) << "Unknown node type";
    }

    hashes[node] = h;

    // Group the node based on its hash value.
    if (groups.find(h) == groups.end()) {
      std::vector<AnfNodePtr> innervec({node});
      groups[h] = innervec;
      order_group.emplace_back(h);
    } else {
      groups[h].push_back(node);
    }
  }

  // Attempt to replace nodes within each group.
  return DoReplace(manager, order_group, &groups);
}

// This function applies the BuildOrderGroupAndDoReplaceForOneGraph operation for all the function graphs 
// managed by the given manager.
// @param manager: The manager for all function graphs to process.
// @return: Whether any of the function graphs were changed.
bool CSE::BuildOrderGroupAndDoReplace(const FuncGraphManagerPtr manager) const {
  bool changed = false;

  // Iterate over all function graphs managed by the manager.
  for (FuncGraphPtr fg : manager->func_graphs()) {
    // Attempt to replace nodes for the current function graph and update the 'changed' status.
    changed = BuildOrderGroupAndDoReplaceForOneGraph(fg, manager) || changed;
  }

  return changed;
}

// Given a list of node groups, this function attempts to replace duplicate nodes within each group.
// Nodes are considered duplicates if they compute the same values.
// @param manager: The manager for the function graph.
// @param order_group: The ordered list of node groups to process.
// @param groups: The mapping of group hashes to lists of nodes.
// @return: Whether any nodes were replaced.
bool CSE::DoReplace(const FuncGraphManagerPtr manager, const std::vector<std::size_t> &order_group,
                    mindspore::HashMap<std::size_t, std::vector<AnfNodePtr>> *groups) const {
  bool changes = false;
  std::set<size_t> clear_set;

  // Iterate over each group.
  for (auto &h : order_group) {
    std::vector<AnfNodePtr> &group = (*groups)[h];

    // If there are more than 1 node in the group, they might represent the same computation.
    if (group.size() > 1) {
      // Check each node against every other node in the group.
      for (size_t k = 0; k < group.size() - 1; k++) {
        AnfNodePtr main = group[k];
        MS_EXCEPTION_IF_NULL(main);

        // Skip nodes that have already been replaced or are value nodes.
        if ((k + 1 + clear_set.size() == group.size()) || (k > 0 && main->isa<ValueNode>())) {
          break;
        }

        if (clear_set.find(k) != clear_set.end()) {
          continue;
        }

        for (size_t i = k + 1; i < group.size(); i++) {
          auto node = group[i];
          MS_EXCEPTION_IF_NULL(node);

          if (clear_set.find(i) != clear_set.end()) {
            continue;
          }

          // Nodes must belong to the same function graph.
          if (main->func_graph() != node->func_graph()) {
            continue;
          }

          // Check if the nodes are equivalent.
          if (CheckReplace(node, main)) {
            changes = true;
            // Optional: Update debug info or dump flags.
            UpdateDebugInfoAndDumpFlag(main, node);
            // Replace the node.
            (void)manager->Replace(node, main);
            (void)clear_set.insert(i);
          }
        }
      }

      clear_set.clear();
    }
  }

  return changes;
}


bool CSE::Cse(const FuncGraphPtr root, const FuncGraphManagerPtr manager) const {
  MS_EXCEPTION_IF_NULL(manager);
  manager->AddFuncGraph(root);
  return BuildOrderGroupAndDoReplace(manager);
}
}  // namespace opt
}  // namespace mindspore