OpenRAM/compiler/base/graph_util.py

import copy
from collections import defaultdict
import debug


class timing_graph():
    """
    Implements a directed graph
    Nodes are currently just Strings.
    """

    def __init__(self):
        self.graph = defaultdict(set)
        self.all_paths = []
        self.edge_mods = {}

    def add_edge(self, src_node, dest_node, edge_mod):
        """Adds edge to graph. Nodes added as well if they do not exist.
           Module which defines the edge must be provided for timing information."""

        src_node = src_node.lower()
        dest_node = dest_node.lower()
        self.graph[src_node].add(dest_node)
        self.edge_mods[(src_node, dest_node)] = edge_mod

    def add_node(self, node):
        """Add node to graph with no edges"""

        node = node.lower()
        if node not in self.graph:
            self.graph[node] = set()

    def remove_edges(self, node):
        """Helper function to remove edges, useful for removing vdd/gnd"""

        node = node.lower()
        self.graph[node] = set()

    def get_all_paths(self, src_node, dest_node, remove_rail_nodes=True, reduce_paths=True):
        """Traverse all paths from source to destination"""

        src_node = src_node.lower()
        dest_node = dest_node.lower()

        # Remove vdd and gnd by default
        # Will require edits if separate supplies are implemented.
        if remove_rail_nodes:
            # Names are also assumed.
            self.remove_edges('vdd')
            self.remove_edges('gnd')

        # Mark all the vertices as not visited
        visited = set()

        # Create an array to store paths
        path = []
        self.all_paths = []

        # Call the recursive helper function to print all paths
        self.get_all_paths_util(src_node, dest_node, visited, path)
        debug.info(2, "Paths found={}".format(len(self.all_paths)))

        if reduce_paths:
            self.reduce_paths()

        return self.all_paths

    def reduce_paths(self):
        """ Remove any path that is a subset of another path """

        self.all_paths = [p1 for p1 in self.all_paths if not any(set(p1)<=set(p2) for p2 in self.all_paths if p1 is not p2)]

    def get_all_paths_util(self, cur_node, dest_node, visited, path):
        """Recursive function to find all paths in a Depth First Search manner"""

        # Mark the current node as visited and store in path
        visited.add(cur_node)
        path.append(cur_node)

        # If current vertex is same as destination, then print
        # current path[]
        if cur_node == dest_node:
            self.all_paths.append(copy.deepcopy(path))
        else:
            # If current vertex is not destination
            # Recur for all the vertices adjacent to this vertex
            for node in self.graph[cur_node]:
                if node not in visited:
                    self.get_all_paths_util(node, dest_node, visited, path)

        # Remove current vertex from path[] and mark it as unvisited
        path.pop()
        visited.remove(cur_node)

    def get_timing(self, path, corner, slew, load):
        """Returns the analytical delays in the input path"""

        if len(path) == 0:
            return []

        delays = []
        cur_slew = slew
        for i in range(len(path) - 1):

            path_edge_mod = self.edge_mods[(path[i], path[i + 1])]

            # On the output of the current stage, get COUT from all other mods connected
            cout = 0
            for node in self.graph[path[i + 1]]:
                output_edge_mod = self.edge_mods[(path[i + 1], node)]
                cout+=output_edge_mod.get_cin()
            # If at the last output, include the final output load
            if i == len(path) - 2:
                cout += load

            #delays.append(path_edge_mod.analytical_delay(corner, cur_slew, cout))
            delays.append(path_edge_mod.cacti_delay(corner, cur_slew, cout))
            cur_slew = delays[-1].slew

        return delays
        
    def get_edge_mods(self, path):
        """Return all edge mods associated with path"""
        
        if len(path) == 0:
            return []
            
        return [self.edge_mods[(path[i], path[i+1])] for i in range(len(path)-1)]    

    def __str__(self):
        """ override print function output """

        str = ""
        for n in self.graph:
            str += n + "\n"
            for d in self.graph[n]:
                str += "\t\t-> " + d + "\n"
        return str

    def __repr__(self):
        """ override print function output """

        return str(self)