Spectral examples sequence

This page gives a reading and running order through three programs that add one concept at a time: a spectral model, simulator orchestration, and a nonlinear model with output.

Sequence

Step	Executable	New idea
1	04_diffusion_model	Subclass Model, implement initialize and step, and apply a Fourier-space operator
2	05_simulator	Add Simulator, Time, field modifiers, and lifecycle orchestration
3	12_cahn_hilliard	Add a nonlinear operator split, initial data, and VTK output

Together they mirror how a research application usually grows: first verify the physics step, then add framework-managed lifecycle and output.

Build and run

From the repository root:

cmake --build build --target \
  04_diffusion_model \
  05_simulator \
  12_cahn_hilliard

mpirun -n 1 ./build/examples/04_diffusion_model
mpirun -n 1 ./build/examples/05_simulator
mpirun -n 1 ./build/examples/12_cahn_hilliard

Begin with one rank. After all three programs exit with status zero, repeat with a rank count supported by your launcher allocation and the example dimensions. The programs do not share one mandatory success message; see Example run output.

Read the sources

File	Look for
examples/04_diffusion_model.cpp	Field allocation, Fourier-space operator construction, and forward/backward transforms
examples/05_simulator.cpp	Simulator construction, modifiers, time control, and ownership
examples/12_cahn_hilliard.cpp	Nonlinear split, initial state, and VTK write cadence

Treat these compiled examples as the code-level source of truth. This page explains their order rather than copying their implementations.

Continue by goal

Goal	Next document
Understand Domain, decomposition, and FFT first	Library basics
Build a JSON-driven application	Minimal custom application
Understand JSON-to-simulator wiring	Application pipeline
Inspect output in ParaView	VTK and ParaView workflow
Find every runnable example	Examples catalog
Look up API-focused snippets	API examples walkthrough