zhangliye / DiscreteEvents.jl

A Julia package for discrete event generation and simulation

DiscreteEvents.jl

A Julia package for discrete event generation and simulation.

DiscreteEvents.jl provides three schemes for modeling and simulating discrete event systems (DES): 1) event scheduling, 2) interacting processes and 3) continuous sampling. It introduces a clock and allows to schedule arbitrary Julia functions or expressions as events, processes or sampling operations on the clock's timeline. Thus it provides simplicity and flexibility in building models and performance in simulation.

A first example

A server takes something from its input and puts it out modified after some time. We implement that in a function, create input and output channels and some "foo" and "bar" processes operating reciprocally on the channels:

using DiscreteEvents, Printf, Random

function simple(c::Clock, input::Channel, output::Channel, name, id, op)
    token = take!(input)         # take something from the input
    now!(c, SF(println, @sprintf("%5.2f: %s %d took token %d", tau(c), name, id, token)))
    d = delay!(c, rand())        # after a delay
    put!(output, op(token, id))  # put it out with some op applied
end

clk = Clock()      # create a clock
Random.seed!(123)  # seed the random number generator

ch1 = Channel(32)  # create two channels
ch2 = Channel(32)

for i in 1:2:8     # create and register 8 SimProcesses SP
    process!(clk, SP(i, simple, ch1, ch2, "foo", i, +))
    process!(clk, SP(i+1, simple, ch2, ch1, "bar", i+1, *))
end

put!(ch1, 1)       # put first token into channel 1
yield()            # let the first task take it
run!(clk, 10)      # and run for 10 time units

If we source this program, it runs a simulation:

julia> include("docs/examples/channels.jl")
 0.00: foo 1 took token 1
 0.77: bar 2 took token 2
 1.71: foo 3 took token 4
 2.38: bar 4 took token 7
 2.78: foo 5 took token 28
 3.09: bar 6 took token 33
 ...
 ...
 7.64: foo 1 took token 631016
 7.91: bar 2 took token 631017
 8.36: foo 3 took token 1262034
 8.94: bar 4 took token 1262037
 9.20: foo 5 took token 5048148
 9.91: bar 6 took token 5048153
"run! finished with 43 clock events, 0 sample steps, simulation time: 10.0"

For further examples see the documentation, or the companion package DiscreteEventsCompanion.

Installation

The development (and sometimes not so stable) version can be installed with:

pkg> add https://github.com/pbayer/DiscreteEvents.jl

The stable, registered version is installed with:

pkg> add DiscreteEvents

Please use, test and help to develop DiscreteEvents.jl! 😄

Author: Paul Bayer