Add support for specifying number of CPU cores

[AsymmetryChou]

Introduce an option to specify the number of CPU cores for parallel self-energy calculations. Update the relevant functions and examples to utilize this new parameter, enhancing performance and flexibility.

[Copilot]

Pull request overview

This PR adds a new n_cpus option to control how many CPU cores are used for parallel lead self-energy calculations in the NEGF runner, and updates the atomic chain CLI example to demonstrate its usage.

Changes:

• Add n_cpus to NEGF task options validation and pass it through the NEGF runner into the self-energy parallelization logic.
• Update self-energy worker selection to use n_cpus (when provided) instead of always relying on os.cpu_count().
• Update the atomic chain CLI example input (and notebook outputs) to use n_cpus=2.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
dpnegf/utils/argcheck.py	Adds n_cpus to NEGF task option schema.
dpnegf/runner/NEGF.py	Accepts/stores n_cpus and forwards it into self-energy computation.
dpnegf/negf/lead_property.py	Uses n_cpus to cap worker count and threads it through self-energy computation helpers.
examples/atomic_chain_cli/input_files/negf_chain_new.json	Demonstrates n_cpus: 2 in example configuration.
examples/atomic_chain_cli/run.ipynb	Updates example run outputs reflecting the new parallel self-energy behavior.

Comments suppressed due to low confidence (2)

dpnegf/negf/lead_property.py:546

• If the user passes an invalid n_cpus value (e.g., 0 or negative), this branch will trigger but the warning message claims os.cpu_count() returned an invalid value. Consider validating n_cpus explicitly (raise or clamp to 1) and adjusting the warning to reflect whether the invalid value came from user input vs os.cpu_count().

    cpu_count = n_cpus if n_cpus is not None else os.cpu_count()
    if cpu_count is None or cpu_count < 1:
        cpu_count = 1
        log.warning("os.cpu_count() returned None or invalid value. Defaulting to 1 CPU core.")

dpnegf/negf/lead_property.py:524

• _get_safe_n_jobs now takes n_cpus but the docstring parameters list doesn’t mention it. Please document n_cpus (and expected values, e.g., positive int) so callers understand the override behavior.

def _get_safe_n_jobs(lead_L, lead_R, requested_n_jobs=-1, max_memory_fraction=0.7, min_workers=1, kpoint=None, n_cpus=None):
    """
    Calculate safe number of parallel workers based on available system memory.

    Parameters

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