JumpSystem

System Constructors

ModelingToolkit.JumpSystem — Type

struct JumpSystem{U<:RecursiveArrayTools.ArrayPartition} <: ModelingToolkit.AbstractSystem

A system of jump processes.

Fields

eqs
The jumps of the system. Allowable types are ConstantRateJump, VariableRateJump, MassActionJump.

iv
The independent variable, usually time.
states
The dependent variables, representing the state of the system.
ps
The parameters of the system.
observed
name
The name of the system.
systems
The internal systems.
default_u0
default_u0: The default initial conditions to use when initial conditions are not supplied in ODEProblem.

default_p
default_p: The default parameters to use when parameters are not supplied in ODEProblem.

Example

using ModelingToolkit

@parameters β γ t
@variables S I R
rate₁   = β*S*I
affect₁ = [S ~ S - 1, I ~ I + 1]
rate₂   = γ*I
affect₂ = [I ~ I - 1, R ~ R + 1]
j₁      = ConstantRateJump(rate₁,affect₁)
j₂      = ConstantRateJump(rate₂,affect₂)
j₃      = MassActionJump(2*β+γ, [R => 1], [S => 1, R => -1])
js      = JumpSystem([j₁,j₂,j₃], t, [S,I,R], [β,γ])

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Composition and Accessor Functions

sys.eqs or equations(sys): The equations that define the jump system.
sys.states or states(sys): The set of states in the jump system.
sys.parameters or parameters(sys): The parameters of the jump system.
sys.iv or independent_variable(sys): The independent variable of the jump system.

Problem Constructors

SciMLBase.DiscreteProblem — Type

function DiffEqBase.DiscreteProblem(sys::JumpSystem, u0map, tspan,
                                    parammap=DiffEqBase.NullParameters; kwargs...)

Generates a blank DiscreteProblem for a pure jump JumpSystem to utilize as its prob.prob. This is used in the case where there are no ODEs and no SDEs associated with the system.

Continuing the example from the JumpSystem definition:

using DiffEqBase, DiffEqJump
u₀map = [S => 999, I => 1, R => 0]
parammap = [β => .1/1000, γ => .01]
tspan = (0.0, 250.0)
dprob = DiscreteProblem(js, u₀map, tspan, parammap)

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DiffEqJump.JumpProblem — Type

function DiffEqBase.JumpProblem(js::JumpSystem, prob, aggregator; kwargs...)

Generates a JumpProblem from a JumpSystem.

Continuing the example from the DiscreteProblem definition:

jprob = JumpProblem(js, dprob, Direct())
sol = solve(jprob, SSAStepper())

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