Basic Examples

GUI Examples

Examples of using the simulation core API via the graphical user interface (sim_gui).

1) Kepler orbits in phase portrait mode

Generate Kepler style orbits in phase portrait mode.

local sim = require("libsimcore")
local N = 512
local dt = 0.05
local ctx = sim.sim_create()

sim.sim_set_timestep(ctx, dt)
sim.sim_set_visual_mode(ctx, "phase_portrait")

local field_1 = sim.sim_add_field(ctx, {N}, {
    type = "complex_double",
    fill = {0.0, 0.0}
})

local field_2 = sim.sim_add_field(ctx, {N}, {
    type = "complex_double",
    fill = {0.0, 0.0}
})

sim.sim_add_stimulus_operator(ctx, field_1, {
    type = "stimulus_sine",
    amplitude = 0.25,
    wavenumber = 0.025,
    omega = -0.3,
    phase = 0
})

sim.sim_add_stimulus_operator(ctx, field_1, {
    type = "stimulus_sine",
    amplitude = 0.25,
    wavenumber = 0.05,
    omega = -0.3,
    phase = math.pi/2,
    rotation = math.pi/4,
})

sim.sim_add_stimulus_operator(ctx, field_2, {
    type = "stimulus_spectral_lines",
    amplitude = 0.25,
    wavenumber = 0.03,
    omega = -0.2,
    phase = 0
})

sim.sim_add_mixer_operator(ctx, field_2, field_1, field_1, {
    mode = "multiply",
    lhs_gain = 0.5,
    rhs_gain = 0.5
})

local integrator = sim.sim_create_context_integrator(ctx, "euler")

sim.sim_set_integrator(ctx, integrator)

return ctx

2) Gaussian pulse

Applies a moving Gaussian pulse stimulus to a real field.

local sim = require("libsimcore")
local N = 768
local dt = 0.025

local ctx = sim.sim_create()

sim.sim_set_timestep(ctx, dt)
sim.sim_set_visual_mode(ctx, "polar")

local field = sim.sim_add_field(ctx, {N}, {
    type = "double",
    fill = {0.0}
})

sim.sim_add_zero_field_operator(ctx, field)

sim.sim_add_stimulus_operator(ctx, field, {
    type = "stimulus_gaussian_plain",
    amplitude = 0.25,
    sigma = 0.75,
    velocity = 1,
    center = math.pi,
    spacing = 0.05
})

local integrator = sim.sim_create_context_integrator(ctx, "euler", {
    initial_dt = dt
})

sim.sim_set_integrator(ctx, integrator)

return ctx

3) Simple log hook

local sim = require("libsimcore")
local N = 512
local dt = 0.01
local ctx = sim.sim_create()

sim.sim_set_timestep(ctx, dt)
sim.sim_on_step(ctx, function(c)
    local t = sim.sim_get_time(c)
    sim.log("t=%.3f", t)
end)

return ctx

Example output in log panel:

[INFO] t=0.000
[INFO] t=0.010
[INFO] t=0.020
[INFO] t=0.030
...

CLI Examples

Examples of using the simulation core API via the command-line interface (sim_cli).

1) Fixed-step sine stimulus

Applies $A\sin(kx - \omega t)$ to a real field and takes 120 integrator (RK4) steps, matching the forced oscillator

$$\dot u(t) = A\sin(kx - \omega t)$$

local sim = require("libsimcore")
local ctx = sim.sim_create()
local steps = 120
local N = 256
local dt = 0.02

sim.log("Starting simulation with %d steps and dt = %.3f", steps, dt)

local field = sim.sim_add_field(ctx, {N}, {
    type = "double",
    fill = {0}
})

sim.sim_add_stimulus_operator(ctx, field, {
    type = "stimulus_sine",
    amplitude = 0.1,
    wavenumber = 1.0,
    omega = 0.2
})

local integrator = sim.sim_create_context_integrator(ctx, "rk4", {
    initial_dt = dt
})

sim.sim_set_integrator(ctx, integrator)

for _ = 1, steps do
    sim.sim_integrator_step(ctx, integrator, dt)
    local values = field:values()
    sim.log("Field sample value: %.6f", values[1])
end

sim.sim_shutdown(ctx)

return ctx

Example output:

oak@field % ./bin/sim_cli --script fixed-step-sine.lua
[INFO] Starting simulation with 120 steps and dt = 0.020
...
[INFO] Field sample value: -0.665682
[INFO] Field sample value: -0.687690
[INFO] Field sample value: -0.710105
[INFO] Field sample value: -0.732928
[INFO] Field sample value: -0.756163
[INFO] Field sample value: -0.779813
[INFO] Field sample value: -0.803878
[INFO] Field sample value: -0.828362
...