SnakesUtils

SnakesUtils supports conversion from SNAKES objects to Built-in Data Types in Python. As a result, the Petri net models can be manipulated more easily for your specific purpose.

Feature

• For a SNAKES object, generate Python list(or dict) of P, T in PN=(P, T).
• For all p in P, t in T, generate t, p as a Python list.
• For all t in T, generate the guard conditions for each as a Python dict.
• For all t in T, generate the input and output places as a Python dict.
• For all p in P, generate the input and output transitons as a Python dict.

PN=(P, T) is a Petrinet as a SNAKES object. P and T are sets of place and transion, respectively.

Getting Started

Installing

% pip install snakes-utils

Example

A very simple example. notebook example here.

from snakes.nets import *
import snakes_utils

# create petri nets
n = PetriNet('sample')
n.add_place(Place('p0', [1]))
n.add_place(Place('p1', [1]))
n.add_transition(Transition('t0'))
n.add_transition(Transition('t1'))
n.add_input('p0', 't0', Variable('x'))
n.add_output('p1', 't0', Variable('x'))
n.add_input('p1', 't1', Variable('x'))

su = snakes_utils.Basic(n)

# Outputs the guard condition for each transition.
print(su.guards)
# {'t0': 'True', 't1': 'True'}

# Outputs input transitions for each place.
print(su.posttrans_place_map)
# {'p0': ['t0'], 'p1': ['t1']}

Prerequisites

• Python :: 3.x

  We have already confirmed the operation of version 3.7. Other versions are also expected to work, but we have not been able to confirm.

Running the tests

% python3 -m unittest

Supported specific topologies

In addition to basic Petri nets, specific topologies are supported. More commonly, the Basic class will be easier to use.

• Job Shop Scheduling Problem(Single Resource Type)

Contributing

Welcome!

Versioning

We use pypi for versioning. For the versions available, see the tags on this repository.

API Reference

class Basic

Basic class deals with simple Petri nets.

Method __init__(self, n)

Initialize the instance of Basic Class, that convert snakes object into Built-in Data Types in Python.

su = snakes_utils.Basic(n)

Call API

• n: SNAKES net model

Method places(self)

Return a list of places.

su = snakes_utils.Basic(n)
print(su.places)
# [<place>,...]

Method trans(self)

Return a list of transitions.

su = snakes_utils.Basic(n)
print(su.trans)
# [<transition>,...]

Method guard(self)

Return the guard conditions for each transition.

su = snakes_utils.Basic(n)
print(su.guard)
# { <transition>: <guard>,... }

Method preplaces_trans_map(self)

Return the input places for each transition.

su = snakes_utils.Basic(n)
print(su.preplaces_trans_map)
# { <transiton>: <place>,... }

Method postplaces_trans_map(self)

Return the output places for each transition.

su = snakes_utils.Basic(n)
print(su.postplaces_trans_map)
# { <transiton>: <place>,... }

Method pretrans_place_map(self)

Return the input transitions for each place.

su = snakes_utils.Basic(n)
print(su.pretrans_place_map)
# { <place>: <transition>,... }

Method posttrans_place_map(self)

Return the output transitions for each place.

su = snakes_utils.Basic(n)
print(su.posttrans_place_map)
# { <place>: <transition>,... }

class JSS

Job Shop Scheduling Problem(JSS), one of the combinatorial optimization problems is handled by Petri nets.

Method __init__(self, n, rflag='r')

Initialize the instance of JSS Class, that convert snakes object into Built-in Data Types in Python.

su = snakes_utils.JSS(n)

Call API

• n: SNAKES net model

• rflag: Resource Flag how to distinguish the resource place from places.

  • Sets the first letter of the resource place name. For example, If one resource place name is m1, rflag=m.

  • Resource place names must be in the form of a single-character char followed by the resource number. e.g.) m1, r2

Method places(self)

Return a list of places.

su = snakes_utils.JSS(n)
print(su.places)
# [<place>,...]

Method trans(self)

Return a list of transitions.

su = snakes_utils.JSS(n)
print(su.trans)
# [<transition>,...]

Method resources(self)

Return a list of resources information. Use only for JSS.

su = snakes_utils.JSS(n)
print(su.resources)
# [<resource>,...]

Method preplaces_trans_map(self, resource=False)

Return the input places for each transition.

su = snakes_utils.JSS(n)
print(su.preplaces_trans_map)
# { <transiton>: <place>,... }

Call API

• bool resouce: Include resouce transition.

Method postplaces_trans_map(self, resource=False)

Return the output places for each transition.

su = snakes_utils.JSS(n)
print(su.postplaces_trans_map)
# { <transiton>: <place>,... }

Call API

• bool resouce: Include resouce transition.

Method pretrans_place_map(self)

Return the input transitions for each place.

su = snakes_utils.JSS(n)
print(su.pretrans_place_map)
# { <place>: <transition>,... }

Method posttrans_place_map(self)

Return the output transitions for each place.

su = snakes_utils.JSS(n)
print(su.posttrans_place_map)
# { <place>: <transition>,... }

Method trans_resource_map(self)

Return a set of transitions that need resources. Use only for JSS.

su = snakes_utils.JSS(n)
print(su.trans_resource_map)
# {<resource>: {<transition>, ...}, ...},

Method resources_trans_map(self)

Return a set of machines that need transitions. Use only for JSS.

su = snakes_utils.JSS(n)
print(su.resources_trans_map)
# {<transition>: {<resource>, ...}, ...},

Method pt(self)

Return the processing time for each operation. Use only for JSS.

su = snakes_utils.JSS(n)
print(su.pt)
# {<transition>: <processing time>,...},

Method jobs(self)

Return operations for each jobs. The job number is determined dynamically. Use only for JSS.

su = snakes_utils.JSS(n)
print(su.jobs)
# { job_number: [trans_id,...],... }

Reference site

• https://snakes.ibisc.univ-evry.fr/
• https://github.com/fpom/snakes

License

The source code is licensed LGPL.

(C) 2021-2022 Kohei Kaneshima

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.

This library 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 Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; If not, see https://www.gnu.org/licenses/.