diff --git a/README.md b/README.md
new file mode 100644
index 0000000000000000000000000000000000000000..87de015ded026f348a4c368c7b2c0aff28537e13
--- /dev/null
+++ b/README.md
@@ -0,0 +1,40 @@
+SimpleKit for Ruby is a minimalist implementation of discrete event
+simulation using event graphs.
+
+Copyright (C) 2012-2018 Paul J. Sanchez
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the MIT free software license.
+
+**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.**
+
+### DESCRIPTION
+
+SimpleKit for Ruby is a very minimal Ruby implementation of discrete event
+simulation based on Lee Schruben's "Event Graph" approach. I wrote it to
+illustrate to CS students how simulation works "under the hood". You are
+welcome to use it as you wish so long as you clearly understand that it was
+created to be a teaching tool. For serious simulation modeling with event
+graphs I recommend Lee Schruben's `SIGMA` package or Arnie Buss's `SimKit`.
+
+### WHAT'S WHAT
+
+This top level folder contains this file, `README.md`, and the
+`simplekit.gemspec` used to create the gem installation.
+
+To install `SimpleKit` for Ruby, use Ruby's `gem` command:
+
+ gem build simplekit.gemspec
+ gem install simplekit-<version>.gem
+
+(You may need to authenticate as an administrator to install gems.)
+
+There are two subdirectories. Source code for `SimpleKit` can be found
+in `lib/simplekit.rb`. Local documentation can be generated using Ruby's
+`rdoc` command or `yard`.
+
+Examples can be found in the `demos` folder, which contains several relatively simple models to
+illustrate `SimpleKit` usage. These include samples of
+event scheduling, both with and without arguments, and event cancellation.
diff --git a/ReadMe.1st b/ReadMe.1st
deleted file mode 100644
index 873ee6506806538bb554059abe3ae5df39b1bacd..0000000000000000000000000000000000000000
--- a/ReadMe.1st
+++ /dev/null
@@ -1,43 +0,0 @@
-SimpleKit-ruby is a minimalist Ruby library which implements discrete event
-simulation using event graphs.
-
-Copyright (C) 2012-2017 Paul J. Sanchez
-
-This library is free software; you can redistribute it and/or
-modify it under the terms of the MIT free software license.
-
-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.
-
-DESCRIPTION
-
-SimpleKit-ruby is a very minimal Ruby implementation of discrete event
-simulation based on Lee Schruben's "Event Graph" approach. I wrote it
-to illustrate to CS students how simulation works. You are welcome to
-use it as long as you clearly understand that it was designed as a
-teaching tool. For serious simulation modeling with event graphs I
-recommend Lee Schruben's SIGMA package or Arnie Buss's SimKit.
-
-WHAT'S WHAT
-
-This top level folder contains this file, "ReadMe.1st", the
-simplekit.gemspec used to create the gem installation.
-
-To install SimpleKit-ruby, use Ruby's "gem" command:
-
- gem build simplekit.gemspec
- gem install simplekit-<version>.gem
-
-You may need to authenticate as an administrator to install gems.
-
-There are two subdirectories. Source code for SimpleKit-ruby can be found
-in lib/simplekit.rb. Documentation can be generated using Ruby's
-rdoc command.
-
-The second subdirectory is "demos", and contains three simple models to
-illustrate SimpleKit-ruby usage. "MyModel.rb" demonstrates basic event
-scheduling and halting the model. "MyModelArgs.rb" uses random times
-for the event scheduling, and shows how to schedule with arguments for
-the event methods. Finally, "MMk.rb" implements an M/M/k queueing
-model.
diff --git a/demos/AoModel.rb b/demos/AoModel.rb
index a7649e4f883dbf8af3542f85ca7b705363ac3427..99a1c0f6e6c2180ec46903eb02c7a4b3d5be0bd7 100644
--- a/demos/AoModel.rb
+++ b/demos/AoModel.rb
@@ -1,6 +1,5 @@
#!/usr/bin/env ruby
-require 'rubygems' if RUBY_VERSION =~ /^1\.8/
require_relative '../lib/simplekit'
# Demonstration model of Operational Availability (Ao).
diff --git a/demos/CancelQ.rb b/demos/CancelQ.rb
new file mode 100644
index 0000000000000000000000000000000000000000..7880f7017c4c30ce8f56e133c309c1dad391a070
--- /dev/null
+++ b/demos/CancelQ.rb
@@ -0,0 +1,22 @@
+#!/usr/bin/env ruby
+
+require_relative '../lib/simplekit'
+
+class MyModel
+ include SimpleKit
+
+ def init
+ @x = 1
+ schedule(:increment, rand(2), n: 1, char: 'z'.ord)
+ cancel(:increment, char: 'q'.ord)
+ end
+
+ def increment(n:, char:)
+ @x += n
+ printf "%f, %f, %c\n", model_time, @x, char
+ schedule(:increment, 2.0 * rand(2), n: @x, char: char - 1, priority: 3)
+ end
+end
+
+srand(42)
+MyModel.new.run
diff --git a/demos/MMk.rb b/demos/MMk.rb
index 90b37062778ebf886e8c22c0c3615ba3ff1b5619..241f34b1122064c9e064a801e2d752dff2e1c7d7 100644
--- a/demos/MMk.rb
+++ b/demos/MMk.rb
@@ -1,6 +1,5 @@
#!/usr/bin/env ruby
-require 'rubygems' if RUBY_VERSION =~ /^1\.8/
require_relative '../lib/simplekit'
# Demonstration model of an M/M/k queueing system. There are k servers
diff --git a/demos/MMk_shutdown.rb b/demos/MMk_shutdown.rb
new file mode 100644
index 0000000000000000000000000000000000000000..78c24487c2ccf5555b6dacf48014174f15bc183e
--- /dev/null
+++ b/demos/MMk_shutdown.rb
@@ -0,0 +1,80 @@
+#!/usr/bin/env ruby
+
+require_relative '../lib/simplekit'
+
+# Demonstration model of an M/M/k queueing system. There are k servers
+# and both the arrival and service processes are memoryless (exponential).
+class MMk
+ include SimpleKit
+
+ # Constructor - initializes the model parameters.
+ # param: arrival_rate - The rate at which customers arrive to the system.
+ # param: service_rate - The rate at which individual servers serve.
+ # param: max_servers - The total number of servers in the system.
+ def initialize(arrival_rate, service_rate, max_servers)
+ @arrival_rate = arrival_rate
+ @service_rate = service_rate
+ @max_servers = max_servers
+ end
+
+ # Initialize the model state and schedule any necessary events.
+ # Note that this particular model will terminate based on
+ # time by scheduling a halt 100 time units in the future.
+ def init
+ @num_available_servers = @max_servers
+ @q_length = 0
+ schedule(:arrival, 0.0)
+ schedule(:close_doors, 100.0)
+ dump_state('init')
+ end
+
+ # An arrival event increments the queue length, schedules the next
+ # arrival, and schedules a begin_service event if a server is available.
+ def arrival
+ @q_length += 1
+ schedule(:arrival, exponential(@arrival_rate))
+ schedule(:begin_service, 0.0) if @num_available_servers > 0
+ dump_state('arrival')
+ end
+
+ # Start service for the first customer in line, removing that
+ # customer from the queue and utilizing one of the available servers.
+ # An end_service will be scheduled.
+ def begin_service
+ @q_length -= 1
+ @num_available_servers -= 1
+ schedule(:end_service, exponential(@service_rate))
+ dump_state('begin svc')
+ end
+
+ # Frees up an available server, and schedules a begin_service if
+ # anybody is waiting in line.
+ def end_service
+ @num_available_servers += 1
+ schedule(:begin_service, 0.0) if @q_length > 0
+ dump_state('end svc')
+ end
+
+ def close_doors
+ cancel(:arrival)
+ end
+
+ # Exponential random variate generator.
+ # param: rate - The rate (= 1 / mean) of the distribution.
+ # returns: A realization of the specified distribution.
+ def exponential(rate)
+ -Math.log(rand) / rate
+ end
+
+ # A report mechanism which dumps the time, current event, and values
+ # of the state variables to the console.
+ # param: event - The name of the event which invoked this method.
+ def dump_state(event)
+ printf "Time: %8.3f\t%10s - Q: %d\tServers Available: %d\n",
+ model_time, event, @q_length, @num_available_servers
+ end
+end
+
+# Instantiate an MMk object with a particular parameterization and run it.
+srand 7_654_321
+MMk.new(4.5, 1.0, 5).run
diff --git a/demos/MyModel.rb b/demos/MyModel.rb
index b91fbee2daaf8bb890b6df03febdd2f0d65a5bbf..fa336619e5d494290b01ea2ca07a73cb09c1cf87 100644
--- a/demos/MyModel.rb
+++ b/demos/MyModel.rb
@@ -1,7 +1,6 @@
#!/usr/bin/env ruby
-require 'rubygems' if RUBY_VERSION =~ /^1\.8/
-require 'simplekit'
+require_relative '../lib/simplekit'
class MyModel
include SimpleKit
diff --git a/demos/MyModelArgs.rb b/demos/MyModelArgs.rb
index 1af10706df56b50ac426c4a6d18e14b985a5fe7b..db78ae0dafacd36f44dac3bd12eddd2a9a9287af 100644
--- a/demos/MyModelArgs.rb
+++ b/demos/MyModelArgs.rb
@@ -1,6 +1,5 @@
#!/usr/bin/env ruby
-require 'rubygems' if RUBY_VERSION =~ /^1\.8/
require_relative '../lib/simplekit'
class MyModel
@@ -8,14 +7,14 @@ class MyModel
def init
@x = 1
- schedule(:increment, rand(2), 1, 97)
+ schedule(:increment, rand(2), n: 1, char: 'z'.ord)
end
- def increment(n, c)
+ def increment(n:, char:)
@x += n
- schedule(:increment, 2.0 * rand(2), @x, c + 1)
- printf "%f, %f, %c\n", model_time, @x, c
- schedule(:halt, 0.0) if model_time > 10
+ schedule(:increment, 2.0 * rand(2), n: @x, char: char - 1, priority: 3)
+ printf "%f, %f, %c\n", model_time, @x, char
+ cancel_all :increment if model_time > 10
end
end
diff --git a/demos/sptf.rb b/demos/sptf.rb
new file mode 100644
index 0000000000000000000000000000000000000000..34b0f0f1b02a15900fd66c4c600469c48f773526
--- /dev/null
+++ b/demos/sptf.rb
@@ -0,0 +1,86 @@
+#!/usr/bin/env ruby
+
+require_relative '../lib/simplekit'
+
+# Create a Customer Struct that will store arrival times and processing times.
+Customer = Struct.new(:arrival_time, :processing_time) do
+ include Comparable
+ # rank customers by their processing times, smallest first.
+ def <=>(other)
+ processing_time <=> other.processing_time
+ end
+end
+
+# Demonstration model of a shortest-processing-time-first queueing system.
+# There are k servers and both the arrival and service processes could
+# be anything.
+class SPTF
+ include SimpleKit
+
+ # Constructor - initializes the model parameters.
+ # param: arrivalRate - The rate at which customers arrive to the system.
+ # param: serviceRate - The rate at which individual servers serve.
+ # param: maxServers - The total number of servers in the system.
+ # param: closeTime - The time the server would like to shut down.
+ def initialize(arrivalRate, serviceRate, maxServers, closeTime)
+ @arrivalRate = arrivalRate
+ @serviceRate = serviceRate
+ @maxServers = maxServers
+ @closeTime = closeTime
+ end
+
+ # Initialize the model state and schedule any necessary events.
+ def init
+ @numAvailableServers = @maxServers
+ @q = PriorityQueue.new
+ schedule(:arrival, 0.0)
+ schedule(:close_doors, @closeTime)
+ end
+
+
+ # An arrival event generates a customer and their associated service
+ # time, adds the customer to the queue, schedules the next arrival,
+ # and schedules a beginService event if a server is available.
+ def arrival
+ @q.push Customer.new(model_time, exponential(@serviceRate))
+ schedule(:arrival, exponential(@arrivalRate))
+ schedule(:beginService, 0.0) if (@numAvailableServers > 0)
+ end
+
+ # Start service for the first customer in line, removing that
+ # customer from the queue and utilizing one of the available
+ # servers. An endService will be scheduled. Report the current
+ # time and how long this customer spent in line.
+ def beginService
+ current_customer = @q.pop
+ @numAvailableServers -= 1
+ schedule(:endService, current_customer.processing_time)
+ printf "%f,%f\n", model_time, model_time - current_customer.arrival_time
+ end
+
+ # Frees up an available server, and schedules a beginService if
+ # anybody is waiting in line. If the line is empty and it's after
+ # the desired closing time, halt the simulation.
+ def endService
+ @numAvailableServers += 1
+ unless @q.empty?
+ schedule(:beginService, 0.0)
+ end
+ end
+
+ # Commence shutdown by denying the next :arrival
+ def close_doors
+ cancel :arrival
+ end
+
+ # Exponential random variate generator.
+ # param: rate - The rate (= 1 / mean) of the distribution.
+ # returns: A realization of the specified distribution.
+ def exponential(rate)
+ -Math.log(rand) / rate
+ end
+end
+
+# Instantiate an SPTF object with a particular parameterization and run it.
+srand(9876543) # set seed for repeatability
+SPTF.new(6, 1.0, 5, 20.0).run
diff --git a/lgpl.txt b/lgpl.txt
deleted file mode 100644
index b1e3f5a2638797271cbc9b91b856c05ed6942c8f..0000000000000000000000000000000000000000
--- a/lgpl.txt
+++ /dev/null
@@ -1,504 +0,0 @@
- GNU LESSER GENERAL PUBLIC LICENSE
- Version 2.1, February 1999
-
- Copyright (C) 1991, 1999 Free Software Foundation, Inc.
- 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
- Everyone is permitted to copy and distribute verbatim copies
- of this license document, but changing it is not allowed.
-
-[This is the first released version of the Lesser GPL. It also counts
- as the successor of the GNU Library Public License, version 2, hence
- the version number 2.1.]
-
- Preamble
-
- The licenses for most software are designed to take away your
-freedom to share and change it. By contrast, the GNU General Public
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diff --git a/lib/priority_queue.rb b/lib/priority_queue.rb
index 0d77512d5061c6ec4b620d23a0e9fd266cc6bd1f..a8d023952c511f82ad6a4a6e20ea201db8427893 100644
--- a/lib/priority_queue.rb
+++ b/lib/priority_queue.rb
@@ -4,6 +4,7 @@ class PriorityQueue
clear
end
+ # Push +element+ onto the priority queue.
def <<(element)
@elements << element
# bubble up the element that we just added
@@ -12,11 +13,13 @@ class PriorityQueue
alias push <<
+ # Inspect the element at the head of the queue.
def peek
# the first element will always be the min, because of the heap constraint
@elements[1]
end
+ # Remove and return the next element from the queue, determined by priority.
def pop
# remove the last element of the list
min = @elements[1]
@@ -26,10 +29,12 @@ class PriorityQueue
min
end
+ # Reset the priority queue to empty.
def clear
@elements = [nil]
end
+ # Return a boolean indicating whether the queue is empty or not
def empty?
@elements.length < 2
end
diff --git a/lib/simplekit.rb b/lib/simplekit.rb
index 5ebfcfa603324d91892c7fa45acc8e5a5096ef38..e4ef4d23b16186275efefbcd3ae3334e0462400c 100644
--- a/lib/simplekit.rb
+++ b/lib/simplekit.rb
@@ -1,15 +1,18 @@
+require 'set'
require_relative 'priority_queue'
# The +SimpleKit+ module provides basic event scheduling capabilities.
#
# Including +SimpleKit+ in your simulation model gives you methods +:run+,
-# +:model_time+, +:schedule+, and +:halt+ as mixins. You <b>MUST NOT</b>
-# provide your own implementations of methods with these names in your model.
-# All but +:run+ are delegated to the +EventScheduler+ class.
+# +:model_time+, +:schedule+, +:cancel+, +:cancel_all+, and +:halt+ as mixins.
+# <b>DO NOT</b> create your own implementations of methods with these names
+# in your model. All but +:run+ are delegated to the +EventScheduler+ class.
module SimpleKit
# The set of module methods to be passed to the EventScheduler
# if not found in the model class.
- DELEGATED_METHODS = [:model_time, :schedule, :halt].freeze
+ DELEGATED_METHODS = %i[
+ model_time schedule cancel cancel_all halt
+ ].freeze
# Run your model by creating a new +EventScheduler+ and invoking its
# +run+ method.
@@ -21,11 +24,7 @@ module SimpleKit
# If a method doesn't exist in the model class, try to delegate it
# to +EventScheduler+.
def method_missing(name, *args)
- if DELEGATED_METHODS.include?(name)
- @my_sim.send(name, *args)
- else
- super
- end
+ DELEGATED_METHODS.include?(name) ? @my_sim.send(name, *args) : super
end
# Class +EventScheduler+ provides the computation engine for a
@@ -43,6 +42,7 @@ module SimpleKit
def initialize(the_model)
@user_model = the_model
@event_list = PriorityQueue.new
+ @cancel_set = {}
end
# Add an event to the pending events list.
@@ -51,24 +51,53 @@ module SimpleKit
# - +event+ -> the event to be scheduled.
# - +delay+ -> the amount of time which should elapse before
# the event executes.
- # - +args+ -> an optional list of arguments to pass to the event
- # at invocation time.
- def schedule(event, delay, *args)
+ # - +args+ -> zero or more named arguments to pass to the event
+ # at invocation time. These should be specified with labels, and
+ # consequently they can be placed in any order.
+ def schedule(event, delay, **args)
raise 'Model scheduled event with negative delay.' if delay < 0
- @event_list.push EventNotice.new(event, @model_time + delay, args)
+ @event_list.push EventNotice.new(event, @model_time, delay, args)
+ end
+
+ # Cancel an individual occurrence of event type +event+.
+ # If no +args+ are provided, the next scheduled occurrence of +event+
+ # is targeted. If a subset of the event's +args+ is provided, they must
+ # all be a match with the corresponding +args+ of the scheduled event
+ # in order for the cancellation to apply, but +args+ which are not
+ # specified do not affect the target event matching.
+ def cancel(event, **args)
+ @cancel_set[event] ||= Set.new
+ @cancel_set[event].add(args.empty? ? nil : args)
+ end
+
+ # Cancel all currently scheduled events of type +event+.
+ def cancel_all(event)
+ if event
+ PriorityQueue.new.tap do |pq|
+ while (event_notice = @event_list.pop)
+ pq.push event_notice unless event_notice.event == event
+ end
+ @event_list = pq
+ end
+ end
end
# Start execution of a model. The simulation +model_time+ is initialized
# to zero and the model is initialized via the mandatory +init+ method.
- # Then loop while events are pending on the +event_list+. The event with
- # the smallest time is popped, +model_time+ is updated to the event time,
- # and the event method is invoked.
+ # Then loop while events are pending on the +event_list+. The event with the
+ # smallest time is popped, +model_time+ is updated to the event time, and
+ # the event method is invoked with the +args+, if any, set by +schedule+.
def run
@model_time = 0.0
@user_model.init
while (current_event = @event_list.pop)
+ next if should_cancel?(current_event)
@model_time = current_event.time
- @user_model.send(current_event.event, *current_event.args)
+ if current_event.args.empty?
+ @user_model.send(current_event.event)
+ else
+ @user_model.send(current_event.event, current_event.args)
+ end
end
end
@@ -77,14 +106,51 @@ module SimpleKit
def halt
@event_list.clear
end
- end
- # This is a private helper Struct for the EventScheduler class.
- # Users should never try to access this directly.
- EventNotice = Struct.new(:event, :time, *:args) do
- include Comparable
- def <=>(other)
- time <=> other.time
+ private
+
+ # Private method that returns a boolean to determine if +event_notice+
+ # represents an event subject to cancellation.
+ def should_cancel?(event_notice)
+ e = event_notice.event
+ if @cancel_set.key? e
+ if @cancel_set[e].include? nil
+ @cancel_set[e].delete nil
+ @cancel_set.delete e if @cancel_set[e].empty?
+ return true
+ else
+ for hsh in @cancel_set[e] do
+ next unless event_notice.args >= hsh
+ @cancel_set[e].delete hsh
+ @cancel_set.delete e if @cancel_set[e].empty?
+ return true
+ end
+ end
+ end
+ false
+ end
+
+ # This is a private helper class for the EventScheduler class.
+ # Users should never try to access this directly.
+ class EventNotice
+ attr_reader :event, :time, :time_stamp, :priority, :args
+
+ def initialize(event, time, delay, args)
+ @event = event
+ @time_stamp = time
+ @time = time + delay
+ @args = args
+ @priority = @args && @args.key?(:priority) ? @args.delete(:priority) : 10
+ end
+
+ include Comparable
+ # Compare EventNotice objects for ordering, first by time,
+ # breaking ties using priority.
+ def <=>(other)
+ (time <=> other.time).tap do |outcome|
+ return priority <=> other.priority if outcome == 0
+ end
+ end
end
end
end
diff --git a/simplekit.gemspec b/simplekit.gemspec
index a9516f9d93ba1bf57f17bceebcf08678d773fd31..b55126520421c292ebc4f89399d5b0d5b61463ea 100644
--- a/simplekit.gemspec
+++ b/simplekit.gemspec
@@ -1,10 +1,10 @@
# -*- ruby -*-
-_VERSION = "0.4.5"
+_VERSION = "1.0.0"
Gem::Specification.new do |s|
s.name = "simplekit"
s.version = _VERSION
- s.date = "2017-12-01"
+ s.date = "2018-07-12"
s.summary = "Discrete event simulation engine."
s.homepage = "https://gitlab.nps.edu/pjsanche/simplekit-ruby.git"
s.email = "pjs@alum.mit.edu"
@@ -14,7 +14,12 @@ Gem::Specification.new do |s|
simplekit.gemspec
lib/simplekit.rb
lib/priority_queue.rb
+ demos/MMk.rb
+ demos/MMk_reference_output.txt
+ demos/MMk_shutdown.rb
+ demos/CancelQ.rb
+ demos/sptf.rb
]
- s.required_ruby_version = '>= 1.8.1'
+ s.required_ruby_version = '>= 2.3.0'
s.license = 'MIT'
end