Construction and Simulation of a Simple Model
In this tutorial, we will simulate a very simple model consisting of a generator and a writer as shown in the block diagram shown below.
Model Simulation
Let us construct the model first. See Model Construction for more detailed information about model construction.
using Causal
# Describe the model
@defmodel model begin
@nodes begin
gen = SinewaveGenerator()
writer = Writer()
end
@branches begin
gen => writer
end
end
In this simple model
, we have a single output sinusoidal wave generator gen
and a writer
. In the script above, we constructed the components, connected them together and constructed the model.
We can specify simulation settings such as whether a simulation log file is be to constructed, model components are to be saved in a file, etc.
simdir = "/tmp"
logtofile = true
reportsim = true
At this point, the model is ready for simulation.
t0 = 0. # Start time
dt = 0.01 # Sampling interval
tf = 10. # Final time
sim = simulate!(model, t0, dt, tf, simdir=simdir, logtofile=logtofile, reportsim=reportsim)
Simulation(state:done, retcode:success, path:/tmp/Simulation-37085bb8-c723-4249-9751-206da508dbc3)
Investigation of Simulation
First, let us observe Simulation
instance sim
. We start with the directory in which all simulation files are saved.
foreach(println, readlines(`ls -al $(sim.path)`))
total 80 drwxr-xr-x 2 juliateam juliateam 4096 May 10 17:06 . drwxrwxrwt 1 root root 28672 May 10 17:06 .. -rw-r--r-- 1 juliateam juliateam 15332 May 10 17:06 e673eb9e-6814-44e9-8ce5-e140cea88326.jld2 -rw-r--r-- 1 juliateam juliateam 21490 May 10 17:06 report.jld2 -rw-r--r-- 1 juliateam juliateam 1160 May 10 17:06 simlog.log
The simulation directory includes a log file simlog.log
which helps the user monitor simulation steps.
# Print the contents of log file
open(joinpath(sim.path, "simlog.log"), "r") do file
for line in readlines(file)
println(line)
end
end
┌ Info: 2021-05-10T17:06:31.089 Started simulation... └ @ Causal /juliateam/.julia/packages/Causal/vOCIT/src/utilities/utils.jl:5 ┌ Info: 2021-05-10T17:06:31.152 Inspecting model... └ @ Causal /juliateam/.julia/packages/Causal/vOCIT/src/utilities/utils.jl:5 ┌ Info: 2021-05-10T17:06:31.165 Done. └ @ Causal /juliateam/.julia/packages/Causal/vOCIT/src/utilities/utils.jl:5 ┌ Info: 2021-05-10T17:06:31.165 Initializing the model... └ @ Causal /juliateam/.julia/packages/Causal/vOCIT/src/utilities/utils.jl:5 ┌ Info: 2021-05-10T17:06:31.369 Done... └ @ Causal /juliateam/.julia/packages/Causal/vOCIT/src/utilities/utils.jl:5 ┌ Info: 2021-05-10T17:06:31.369 Running the simulation... └ @ Causal /juliateam/.julia/packages/Causal/vOCIT/src/utilities/utils.jl:5 ┌ Info: 2021-05-10T17:06:31.436 Done... └ @ Causal /juliateam/.julia/packages/Causal/vOCIT/src/utilities/utils.jl:5 ┌ Info: 2021-05-10T17:06:31.436 Terminating the simulation... └ @ Causal /juliateam/.julia/packages/Causal/vOCIT/src/utilities/utils.jl:5 ┌ Info: 2021-05-10T17:06:31.453 Done. └ @ Causal /juliateam/.julia/packages/Causal/vOCIT/src/utilities/utils.jl:5
report.jld2
file, which includes the information about the simulation and model components, can be read back after the simulation.
julia> using FileIO, JLD2
julia> filecontent = load(joinpath(sim.path, "report.jld2"))
Dict{String, Any} with 9 entries:
"retcode" => :success
"name" => "Simulation-37085bb8-c723-4249-9751-206da508dbc3"
"model/callbacks" => nothing
"model/name" => ""
"clock" => Clock(gen:0.0:0.01:10.0, paused:false)
"model/id" => "9ebc8cc3-02fb-4037-9cb4-c793276583bc"
"components/" => SinewaveGenerator(amp:1.0, freq:1.0, phase:0.0, offset:0…
"path" => "/tmp/Simulation-37085bb8-c723-4249-9751-206da508dbc3"
"state" => :done
julia> clock = filecontent["model/clock"]
ERROR: KeyError: key "model/clock" not found
Analysis of Simulation Data
After the simulation, the data saved in simulation data files, i.e. in the files of writers, can be read back any offline data analysis can be performed.
# Read the simulation data
t, x = read(getnode(model, :writer).component)
# Plot the data
using Plots
plot(t, x, xlabel="t", ylabel="x", label="")
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-juliateam' QPainter::begin: Paint device returned engine == 0, type: 3 QPainter::setCompositionMode: Painter not active QWidget::paintEngine: Should no longer be called QPainter::begin: Paint device returned engine == 0, type: 1
A Larger Model Simulation
Consider a larger model whose block diagram is given below
The script below illustrates the construction and simulation of this model
using Causal
using Plots
# Construct the model
@defmodel model begin
@nodes begin
gen1 = SinewaveGenerator(frequency=2.)
gain1 = Gain()
adder1 = Adder(signs=(+,+))
gen2 = SinewaveGenerator(frequency=3.)
adder2 = Adder(signs=(+,+,-))
gain2 = Gain()
writer = Writer()
gain3 = Gain()
end
@branches begin
gen1[1] => gain1[1]
gain1[1] => adder1[1]
adder1[1] => adder2[1]
gen2[1] => adder1[2]
gen2[1] => adder2[2]
adder2[1] => gain2[1]
gain2[1] => writer[1]
gain2[1] => gain3[1]
gain3[1] => adder2[3]
end
end
# Simulation of the model
simulate!(model, withbar=false)
# Reading and plotting the simulation data
t, x = read(getnode(model, :writer).component)
plot(t, x)
savefig("larger_model_plot.svg"); nothing # hide