Simulation options

Use SimulationOptions to configure numerical and analysis choices while the simulation is OPEN or ENDED. Individual assignments and options.update(**changes) use the same atomic native update. Rust checks each value locally, retains the complete requested configuration, and records what needs preparation. The effective solver fields wait until start().

This gives you room to edit related values in several calls. A schedule or step relationship can be temporarily inconsistent while you work. Reads return your requested values, including after a failed start. At start(), the solver prepares effective defaults, step coupling, flags, threads, and dependent hydraulic geometry, then installs them together if preparation succeeds.

If preparation fails, start() raises ConfigurationError with ordered diagnostics and leaves the prior effective state intact. Repair the requested values and retry. requested_threads is what you asked for; simulation.effective_threads is the prepared worker count. Assigning custom_ellipse_model while OPEN or ENDED marks configuration dirty. The next start() revalidates and atomically rebuilds affected cross sections.

Update related dates together with Simulation.update_schedule(**changes). Omitted dates keep their requested values. The setter checks that dates are finite and representable. At start(), the solver checks start/end ordering, positive duration, whether the report start falls at or after the end, and report step coupling. A report start earlier than the requested start is normalized to the effective start instead of producing a diagnostic. Direct date setters use the same operation.

from datetime import datetime, timedelta

simulation.options.update(
    routing_step=timedelta(seconds=20),
    courant_factor=1.0,
    requested_threads=2,
)
simulation.update_schedule(
    start_time=datetime(2025, 1, 1),
    report_start=datetime(2025, 1, 1, 1),
    end_time=datetime(2025, 1, 2),
)

Typed, generation-bound views over configured SWMM project objects.

All view instances retain the simulation and project generation that created them. They validate that identity before accessing native state, so retained views cannot silently address a subsequently reopened project.

CLASS	DESCRIPTION
`SimulationOptions`	Expose typed numerical and analysis policy for one Project Generation.

SimulationOptions

Expose typed numerical and analysis policy for one Project Generation.

Notes

Duration options use datetime.timedelta. Native Rust owns extraction, local validation, declaration commits, deferred preparation, lifecycle, and atomic effective-state commit. Requested values remain readable while the owner is dirty; effective normalization occurs at Simulation.start().

METHOD	DESCRIPTION
`update`	Atomically update mutable simulation policy fields.

ATTRIBUTE	DESCRIPTION
`allow_ponding`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `bool`
`antecedent_dry_duration`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `timedelta`
`courant_factor`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `float`
`custom_ellipse_model`	Hydraulic model for custom ellipses. Setter lifecycle: `OPEN`, `ENDED`. TYPE: `CustomEllipseModel`
`detailed_reporting_enabled`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `bool`
`groundwater_enabled`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `bool`
`head_tolerance`	Return the dynamic-wave head-convergence tolerance in length units. TYPE: `float`
`inertia_damping`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `InertiaDamping`
`lateral_flow_tolerance`	Return the lateral-flow continuity tolerance as a percent. TYPE: `float`
`lengthening_step`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `timedelta`
`maximum_routing_step`	Return the effective maximum routing step as a duration. TYPE: `timedelta`
`maximum_trials`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `int`
`minimum_conduit_slope`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `float`
`minimum_routing_step`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `timedelta`
`minimum_surface_area`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `float`
`normal_flow_limit`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `NormalFlowLimit`
`quality_enabled`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `bool`
`rainfall_enabled`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `bool`
`rdii_enabled`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `bool`
`report_step`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `timedelta`
`requested_threads`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `int`
`routing_enabled`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `bool`
`routing_step`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `timedelta`
`rule_step`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `timedelta`
`skip_steady_state`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `bool`
`snowmelt_enabled`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `bool`
`surcharge_method`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `SurchargeMethod`
`sweep_end`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `tuple[int, int]`
`sweep_start`	Setter lifecycle: `OPEN`, `ENDED`. TYPE: `tuple[int, int]`
`system_flow_tolerance`	Return the system-flow continuity tolerance as a percent. TYPE: `float`