# Source code for pacman.operations.placer_algorithms.connective_based_placer

```
# Copyright (c) 2017-2019 The University of Manchester
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
import logging
from spinn_utilities.log import FormatAdapter
from spinn_utilities.progress_bar import ProgressBar
from pacman.model.constraints.placer_constraints import (
AbstractPlacerConstraint)
from pacman.model.placements import Placements
from pacman.operations.placer_algorithms import RadialPlacer
from pacman.utilities.algorithm_utilities.placer_algorithm_utilities import (
sort_vertices_by_known_constraints, get_same_chip_vertex_groups)
from pacman.utilities.utility_calls import locate_constraints_of_type
from pacman.utilities.utility_objs import ResourceTracker
logger = FormatAdapter(logging.getLogger(__name__))
class ConnectiveBasedPlacer(RadialPlacer):
""" A radial algorithm that can place a machine graph onto a\
machine using a circle out behaviour from a Ethernet at a given point\
and which will place things that are most connected closest to each\
other
"""
__slots__ = []
[docs] def __call__(self, machine_graph, machine, plan_n_timesteps):
"""
:param MachineGraph machine_graph: The machine_graph to place
:param ~spinn_machine.Machine machine:
The machine with respect to which to partition the application
graph
:param int plan_n_timesteps: number of timesteps to plan for
:return: A set of placements
:rtype: ~pacman.model.placements.Placements
:raise PacmanPlaceException:
If something goes wrong with the placement
"""
# check that the algorithm can handle the constraints
self._check_constraints(machine_graph.vertices)
# Sort the vertices into those with and those without
# placement constraints
placements = Placements()
constrained = list()
unconstrained = set()
for vertex in machine_graph.vertices:
if locate_constraints_of_type(
vertex.constraints, AbstractPlacerConstraint):
constrained.append(vertex)
else:
unconstrained.add(vertex)
# Iterate over constrained vertices and generate placements
progress = ProgressBar(
machine_graph.n_vertices, "Placing graph vertices")
resource_tracker = ResourceTracker(
machine, plan_n_timesteps, self._generate_radial_chips(machine))
constrained = sort_vertices_by_known_constraints(constrained)
vertices_on_same_chip = get_same_chip_vertex_groups(machine_graph)
for vertex in progress.over(constrained, False):
self._place_vertex(
vertex, resource_tracker, machine, placements,
vertices_on_same_chip, machine_graph)
while unconstrained:
# Place the subgraph with the overall most connected vertex
max_connected_vertex = self._find_max_connected_vertex(
unconstrained, machine_graph)
self._place_unconstrained_subgraph(
max_connected_vertex, machine_graph, unconstrained,
machine, placements, resource_tracker, progress,
vertices_on_same_chip)
# finished, so stop progress bar and return placements
progress.end()
return placements
def _place_unconstrained_subgraph(
self, starting_vertex, machine_graph, unplaced_vertices,
machine, placements, resource_tracker, progress,
vertices_on_same_chip):
# pylint: disable=too-many-arguments
# Keep track of all unplaced_vertices connected to the currently
# placed ones
to_do = set()
to_do.add(starting_vertex)
while to_do:
# Find the vertex most connected of the currently-to-be-placed ones
vertex = self._find_max_connected_vertex(to_do, machine_graph)
# Place the vertex
self._place_vertex(
vertex, resource_tracker, machine, placements,
vertices_on_same_chip, machine_graph)
progress.update()
# Remove from collections of unplaced_vertices to work on
unplaced_vertices.remove(vertex)
to_do.remove(vertex)
# Add all unplaced_vertices connected to this one to the set
for edge in machine_graph.get_edges_ending_at_vertex(vertex):
if edge.pre_vertex in unplaced_vertices:
to_do.add(edge.pre_vertex)
for edge in machine_graph.get_edges_starting_at_vertex(vertex):
if edge.post_vertex in unplaced_vertices:
to_do.add(edge.post_vertex)
@staticmethod
def _find_max_connected_vertex(vertices, graph):
max_connected_vertex = None
max_weight = 0
for vertex in vertices:
in_weight = sum(
edge.pre_vertex.vertex_slice.n_atoms
for edge in graph.get_edges_starting_at_vertex(vertex))
out_weight = sum(
edge.pre_vertex.vertex_slice.n_atoms
for edge in graph.get_edges_ending_at_vertex(vertex))
weight = in_weight + out_weight
if max_connected_vertex is None or weight > max_weight:
max_connected_vertex = vertex
max_weight = weight
return max_connected_vertex
```