Advanced Usage

This page summarizes the execution-feedback options available for long-running ProcessTensors.jl workflows such as build_process_tensor, create_instruments, evaluate_process, evolve, and tebd.

Progress and verbose output

These workflows support two independent options:

progress = :auto
verbose = false

progress controls transient terminal feedback such as spinners and progress bars.
verbose controls persistent informational logs that remain after the calculation finishes.

`progress`	`verbose`	Behaviour	Recommended use
`false`	`false`	No live display or informational logs	Benchmarks, tests, parameter sweeps, and performance-sensitive runs
`false`	`true`	Persistent milestone logs without animation	Remote servers, HPC jobs, batch scripts, and redirected logs
`true`	`false`	Transient spinner and progress bars	Interactive local runs, tutorials, and demonstrations
`true`	`true`	Live progress together with persistent logs	Local debugging and development
`:auto`	`false`	Enable progress only in a suitable interactive terminal	Recommended default

A normal local run can use the defaults:

pt = build_process_tensor(
    system;
    environment=bath,
    dt=0.05,
    nsteps=100,
)

For a remote or headless calculation:

pt = build_process_tensor(
    system;
    environment=bath,
    dt=0.05,
    nsteps=100,
    progress=false,
    verbose=true,
)

For a silent, performance-oriented run:

pt = build_process_tensor(
    system;
    environment=bath,
    dt=0.05,
    nsteps=100,
    progress=false,
    verbose=false,
)

With verbose=true, the package records major algorithmic milestones without printing one message per timestep. Warnings and errors remain persistent regardless of the values of progress and verbose.

Runnable terminal demonstrations are available under scripts/terminal/ in the package repository.

Threading and dynamic progress display

When progress is enabled, a long workflow may display a transient two-line status:

◓ Building process tensor — assembling cores    Time: 0:00:08
43%|██████████            | 43/100  t=2.15  χ=128

The first line shows the current stage and elapsed time. The second may show a known-length progress bar together with compact quantities already available to the algorithm, such as simulation time or maximum bond dimension.

The display is erased when the operation finishes, after which Julia handles the returned object normally.

The spinner uses only Julia execution threads that were available when Julia started. It prefers an interactive thread when one exists (via the julia call julia -t 3,1 <script>.jl), otherwise another available Julia thread or a cooperative task.

On a single-threaded Julia session, the spinner updates whenever the numerical calculation yields control. During a long non-yielding operation, the latest spinner frame may remain visible until that operation finishes. This affects only the smoothness of the animation, not the result.

The progress backend does not change BLAS thread counts, launch external processes, alter numerical algorithms, or create additional Julia threads at runtime.

No special threading setup is required. Users already running Julia with multiple threads may see smoother animation:

julia --threads=auto --project=. script.jl

Use progress=false when all available resources should be devoted to the scientific calculation.