Merge pull request #53 from antonionevado/simplify_optimizer

Added pattern matching and new optimization passes

dlk/python/dlk/core/graph_pattern_matching.py

@@ -0,0 +1,98 @@
+# -*- coding: utf-8 -*-
+# Copyright 2019 The Blueoil Authors. All Rights Reserved.
+#
+# 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.
+# =============================================================================
+"""Graph sorting helper functions."""
+
+
+def sort_graph(graph):
+    """Helper function to topologically sort a given graph.
+
+    Parameters
+    ----------
+    graph : Graph
+        The input graph to be sorted. It is not modified.
+
+    Returns
+    -------
+    result : [Operator]
+        A list of Operator. Each element of the list is a reference to a Operator object.
+    """
+    exec_list = list()
+    input_nodes = list()
+    for node in graph.operators:
+        input_nodes += [n.name for n in node.input_nodes]
+
+    output_nodes = list()
+    for node in graph.operators:
+        if node not in input_nodes:
+            output_nodes.append(node)
+
+    visited = {}
+    for node in graph.operators:
+        visited[node.name] = False
+
+    for node in output_nodes:
+        top_order(node, exec_list, visited)
+
+    return exec_list
+
+
+def top_order(output_node, exec_list, visited):
+    """It topologically sorts a given graph.
+
+    Parameters
+    ----------
+    output_node : Operator
+        The starting node. First one in the ordered list.
+
+    exec_list : [Operator]
+        The ordered list. Note that this is an output parameter.
+
+    visited : [str]
+        List of already visited nodes.
+    """
+    if visited[output_node.name]:
+        return
+    for input_node in output_node.input_nodes:
+        top_order(input_node, exec_list, visited)
+
+    exec_list.append(output_node)
+    visited[output_node.name] = True
+
+
+def get_nodes_in_branch(starting_node, stop_node, node_list):
+    """Helper function that gives us all nodes in a branch defined by a given node.
+       The starting node will be the output node of the branch.
+
+       Note that there is an optional stop node. stop_node is allowed to be None.
+
+    Parameters
+    ----------
+    starting_node : Operator
+        The starting node. This node is the output node of the defined branch.
+
+    stop_node : Operator
+        The last node in the path. If stop_node is None then this function will give us every node above
+        starting_node.
+
+    node_list : [Operator]
+        The list of nodes contained in the branch. Note that this is an output parameter.
+    """
+    if starting_node == stop_node:
+        return
+    node_list.append(starting_node)
+
+    for node in starting_node.input_nodes:
+        get_nodes_in_branch(node, stop_node, node_list)