# Driver

## Solver types and functions

ClimateMachine.HEVISplittingType
HEVISplitting

HEVI (horizontally explicit, vertically implicit) type method, where vertical acoustic waves are treated implicitly. All other dynamics are treated explicitly.

Note: Can potentially imagine several different types of HEVI splittings (for example, include vertical momentum and/or diffusion)

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ClimateMachine.MISSolverTypeType

Description

MISSolverType(;
splitting_type = SlowFastSplitting(),
fast_model = AtmosAcousticGravityLinearModel,
mis_method = MIS2,
fast_method = LSRK54CarpenterKennedy,
nsubsteps = 50,
)

This solver type constructs an ODE solver using a generalization of the split-explicit Runge-Kutta method. Known as the Multirate Infinitesimal Step (MIS) method, this solver solves ODEs with the partitioned form:

$$$\dot{Q} = f_{fast}(Q, t) + f_{slow}(Q, t)$$$

where the right-hand-side functions f_fast and f_slow denote fast and slow dynamics respectively, depending on the state Q.

Arguments

• splitting_type (DiscreteSplittingType): The type of discrete splitting to apply to the right-hand side. Default: SlowFastSplitting()
• fast_model (Type): The model describing fast dynamics. Default: AtmosAcousticGravityLinearModel
• mis_method (Function): Function defining the particular MIS method to be used. Default: MIS2
• fast_method (Function): Function defining the fast solver. Default: LSRK54CarpenterKennedy
• nsubsteps (Tuple): Tuple denoting the total number of times to substep the fast process. Default: (50,)
• discrete_splitting (Boolean): Boolean denoting whether a PDE level or discretized level splitting should be used. If true then the PDE is discretized in such a way that f_fast + f_slow is equivalent to discretizing the original PDE directly. Default: false

References

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ClimateMachine.MultirateSolverTypeType

Description

MultirateSolverType(;
splitting_type = SlowFastSplitting(),
fast_model = AtmosAcousticGravityLinearModel,
implicit_solver = ManyColumnLU,
slow_method = LSRK54CarpenterKennedy,
fast_method = LSRK54CarpenterKennedy,
timestep_ratio = 100,
)

This solver type constructs an ODE solver using a standard multirate Runge-Kutta implementation. This solver computes solutions to ODEs with the partitioned form:

$$$\dot{Q} = f_{fast}(Q, t) + f_{slow}(Q, t)$$$

where the right-hand-side functions f_fast and f_slow denote fast and slow dynamics respectively, depending on the state Q.

Arguments

• splitting_type (DiscreteSplittingType): The type of discrete splitting to apply to the right-hand side. Default: SlowFastSplitting()
• fast_model (Type): The model describing fast dynamics. Default: AtmosAcousticGravityLinearModel
• implicit_solver (Type): An implicit solver for inverting the implicit system of equations (if using HEVISplitting()). Default: ManyColumnLU
• implicit_solver_adjustable (Bool): A flag identifying whether or not the implicit_solver can be updated as the time-step size changes. This is particularly important when using an implicit solver within a multirate scheme. Default: false
• slow_method (Function): Function defining the particular explicit Runge-Kutta method to be used for the slow processes. Default: LSRK54CarpenterKennedy
• fast_method (Function): Function defining the fast solver. Depending on the choice of splitting_type, this can be an explicit Runge Kutta method or a 1-D IMEX (additive Runge-Kutta) method. Default: LSRK54CarpenterKennedy
• timestep_ratio (Int): Integer denoting the ratio between the slow and fast time-step sizes. Default: 100
• discrete_splitting (Boolean): Boolean denoting whether a PDE level or discretized level splitting should be used. If true then the PDE is discretized in such a way that f_fast + f_slow is equivalent to discretizing the original PDE directly.

References

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ClimateMachine.ExplicitSolverTypeType

Description

ExplicitSolverType(;
solver_method = LSRK54CarpenterKennedy,
)

This solver type constructs an ODE solver using an explicit Runge-Kutta method.

Arguments

• solver_method (Function): Function defining the explicit Runge-Kutta solver. Default: LSRK54CarpenterKennedy
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ClimateMachine.ImplicitSolverTypeType

Description

ImplicitSolverType(;
solver_method = KenCarp4,
)

This solver type constructs an ODE solver using a fully implicit method.

Arguments

• solver_method (Function): Function defining the implicit solver. Default: KenCarp4
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ClimateMachine.SplitExplicitSolverTypeType

Description

SplitExplicitSolverType

This solver type constructs an ODE solver using the SplitExplicitLSRK2nSolver.

Arguments

• dt_slow (AbstractFloat): Time step for the slow solver
• dt_fast (AbstractFloat): Time step for the fast solver
• slow_method (Function): Function defining the explicit Runge-Kutta solver for the slow model. Default: LSRK54CarpenterKennedy
• fast_method (Function): Function defining the explicit Runge-Kutta solver for the fast model. Default: LSRK54CarpenterKennedy
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ClimateMachine.IMEXSolverTypeType

Description

IMEXSolverType(;
splitting_type = HEVISplitting(),
implicit_model = AtmosAcousticGravityLinearModel,
implicit_solver = ManyColumnLU,
solver_method = ARK2GiraldoKellyConstantinescu,
solver_storage_variant = LowStorageVariant(),
split_explicit_implicit = false,
discrete_splitting = true,
)

This solver type constructs a solver for ODEs with the additively-partitioned form. When split_explicit_implicit == false the equation is assumed to be decomposed as

$$$\dot{Q} = [l(Q, t)] + [f(Q, t) - l(Q, t)]$$$

where Q is the state, f is the full tendency and l is the chosen implicit operator.

When split_explicit_implicit == true the assumed decomposition is

$$$\dot{Q} = [l(Q, t)] + [n(Q, t)]$$$

where n is now only the nonlinear tendency.

Arguments

• splitting_type (DiscreteSplittingType): The type of discrete splitting to apply to the right-hand side. Default: HEVISplitting()
• implicit_model (Type): The model describing dynamics to be treated implicitly. Default: AtmosAcousticGravityLinearModel
• implicit_solver (Type): A solver for inverting the implicit system of equations. Default: ManyColumnLU
• implicit_solver_adjustable (Bool): A flag identifying whether or not the implicit_solver can be updated as the time-step size changes. Default: false
• solver_method (Function): Function defining the particular additive Runge-Kutta method to be used for the IMEX method. Default: ARK2GiraldoKellyConstantinescu
• solver_storage_variant (Type): Storage type for the additive Runge-Kutta method. Default: LowStorageVariant()
• split_explicit_implicit (Boolean): Whether the tendency is split in explicit and implicit parts or not.
• discrete_splitting (Boolean): Boolean denoting whether a PDE level or discretized level splitting should be used. If true then the PDE is discretized in such a way that f_fast + f_slow is equivalent to discretizing the original PDE directly.

References

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ClimateMachine.HEVISolverTypeType

Description

HEVISolverType(FT;
solver_method = ARK2ImplicitExplicitMidpoint,

linear_max_subspace_size = Int(30)
linear_atol = FT(-1.0)
linear_rtol = FT(5e-5)

nonlinear_max_iterations = Int(10)
nonlinear_rtol = FT(1e-4)
nonlinear_ϵ = FT(1.e-10)
preconditioner_update_freq = Int(50)
)

This solver type constructs a solver for ODEs with the additively horizontal explicit vertical explicit~(HEVI) partitioned form. the equation is assumed to be decomposed as

$$$\dot{Q} = [l(Q, t)] + [f(Q, t) - l(Q, t)]$$$

where Q is the state, f is the full tendency and l is the vertical implicit operator. The splitting is done automatically.

Arguments

• solver_method (Function): Function defining the particular additive Runge-Kutta method to be used for the HEVI method. Default: ARK2ImplicitExplicitMidpoint
• linear_max_subspace_size (Int): maximal dimension of each (batched) Krylov subspace. GEMRES, a iterative linear solver is applied Default: 30
• linear_atol (FT): absolute tolerance for linear solver convergence. Default: -1.0
• linear_rtol (FT): relative tolerance for linear solver convergence. Default: 5.0e-5
• nonlinear_max_iterations (Int): max number of Newton iterations Default: 10
• nonlinear_rtol (FT): relative tolerance for nonlinear solver convergence. Default: 1e-4
• nonlinear_ϵ (FT): parameter denoting finite different step size for the Jacobian approximation. Default: 1e-10
• preconditioner_update_freq (Int): Int denoting how frequent you need to update the preconditioner -1: no preconditioner; positive number, update every freq times. Default: 50
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ClimateMachine.getdtmodelFunction
getdtmodel(ode_solver::AbstractSolverType, bl)

A function which returns a model representing the dynamics with the most restrictive time-stepping requirements.

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getdtmodel(ode_solver::AbstractSolverType, bl)

A function which returns a model representing the dynamics with the most restrictive time-stepping requirements.

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getdtmodel(ode_solver::AbstractSolverType, bl)

A function which returns a model representing the dynamics with the most restrictive time-stepping requirements.

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getdtmodel(ode_solver::IMEXSolverType, bl)

A function which returns a model representing the dynamics with the most restrictive time-stepping requirements.

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getdtmodel(ode_solver::HEVISolverType, bl)

A function which returns a model representing the dynamics with the most restrictive time-stepping requirements.

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getdtmodel(ode_solver::MultirateSolverType, bl)

A function which returns a model representing the dynamics with the most restrictive time-stepping requirements.

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getdtmodel(ode_solver::MISSolverType, bl)

A function which returns a model representing the dynamics with the most restrictive time-stepping requirements.

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getdtmodel(ode_solver::AbstractSolverType, bl)

A function which returns a model representing the dynamics with the most restrictive time-stepping requirements.

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## Configurations

ClimateMachine.InterpolationConfigurationFunction
InterpolationConfiguration(
driver_config::DriverConfiguration,
boundaries::Array,
resolution = nothing;
axes = nothing;
)

Creates an InterpolationTopology (either an InterpolationBrick or an InterpolationCubedSphere) to be used with a DiagnosticsGroup. Either resolution is specified, in which case the axes are set up with equi-distant points, or the axes may be specified directly (in lat/lon/lvl or x/y/z order).

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ClimateMachine.ConservationCheckType
ClimateMachine.ConservationCheck

Pass a tuple of these to ClimateMachine.invoke! to perform a conservation check of each varname at the specified interval. This computes Σv = weightedsum(Q.varname) and δv = (Σv - Σv₀) / Σv. invoke! throws an error if abs(δv) exceeds error_threshold. Ifshow,δv is displayed.

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## Initialize / solve

ClimateMachine.array_typeFunction
ClimateMachine.array_type()

Return the array type used by ClimateMachine. This defaults to (CPU-based) Array and is only correctly set (based on choice from the command line, from an environment variable, or from experiment code) after ClimateMachine.init() is called.

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ClimateMachine.initFunction
ClimateMachine.init(;
parse_clargs::Bool = false,
custom_clargs::Union{Nothing, ArgParseSettings} = nothing,
init_driver::Bool = true,
keyword_args...,
)

Initialize the ClimateMachine. If parse_clargs is set, parse command line arguments (additional driver-specific arguments can be added by specifying custom_clargs).

Setting init_driver = false will set up the ClimateMachine.Settings singleton values without initializing the ClimateMachine runtime. Otherwise, the runtime will be initialized (see init_runtime()).

Finally, key-value pairs can be supplied to ClimateMachine.init() to set system default settings – the final settings are decided as follows (in order of precedence):

1. Command line arguments (if parse_clargs = true).
2. Environment variables.
3. Keyword arguments to init().
4. Defaults (in ClimateMachine_Settings).

Recognized keyword arguments are:

• disable_gpu::Bool = false: do not use the GPU
• show_updates::String = "60secs": interval at which to show simulation updates
• start_datetime::DateTime = DateTime(2000, 1, 1, 12): date/time at which the simulation starts
• diagnostics::String = "never": interval at which to collect diagnostics"
• no_overwrite::Bool = false: throw an error if an output file would be overwritten
• vtk::String = "never": interval at which to write simulation vtk output
• vtk-number-sample-points::Int = 0: the number of sampling points in each element for VTK output
• monitor_timestep_duration::String = "never": interval in time-steps at which to output wall-clock time per time-step
• monitor_courant_numbers::String = "never": interval at which to output acoustic, advective, and diffusive Courant numbers
• adapt-timestep::String = "never": interval at which to update the timestep
• checkpoint::String = "never": interval at which to write a checkpoint
• checkpoint_keep_one::Bool = true: (interval) keep all checkpoints (instead of just the most recent)
• checkpoint_at_end::Bool = false: create a checkpoint at the end of the simulation
• checkpoint_on_crash::Bool = false: create a checkpoint on a kernel crash (hurts performance!)
• checkpoint_dir::String = "checkpoint": absolute or relative path to checkpoint directory
• restart_from_num::Int = -1: checkpoint number from which to restart (in checkpoint_dir)
• fix_rng_seed::Bool = false: set RNG seed to a fixed value for reproducibility
• log_level::String = "INFO": log level for ClimateMachine global default runtime logger
• disable_custom_logger::String = false: disable using a global custom logger for ClimateMachine
• output_dir::String = "output": (path) absolute or relative path to output data directory
• debug_init::Bool = false: fill state arrays with NaNs and dump them post-initialization
• integration_testing::Bool = false: enable integration_testing
• sim_time::Float64 = NaN: run for the specified time (in simulation seconds)
• fixed_number_of_steps::Int = -1: if ≥0 perform specified number of steps
• degree::NTuple{2, Int} = (-1, -1): tuple of horizontal and vertical polynomial degrees for spatial discretization order
• cutoff_degree::NTuple{2, Int} = (-1, -1): tuple of horizontal and vertical polynomial degrees for cutoff filter
• nelems::NTuple{3, Int} = (-1, -1, -1): tuple of number of elements in each direction: 3 for Ocean, 2 for GCM or 1 for single-stack
• domain_height::Float64 = -1: domain height (in meters) for GCM or single-stack configurations
• resolution::NTuple{3, Float64} = (-1, -1, -1): tuple of three element resolutions (in meters) for LES and MultiColumnLandModel configurations
• domain_min::NTuple{3, Float64} = (-1, -1, -1): tuple of three minima for the domain size (in meters) for LES and MultiColumnLandModel configurations
• domain_max::NTuple{3, Float64} = (-1, -1, -1): tuple of three maxima for the domain size (in meters) for LES and MultiColumnLandModel configurations

Returns nothing, or if parse_clargs = true, returns parsed command line arguments.

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ClimateMachine.invoke!Function
ClimateMachine.invoke!(
solver_config::SolverConfiguration;
diagnostics_config = nothing,
user_callbacks = (),
user_info_callback = () -> nothing,
check_cons = (),
check_euclidean_distance = false,
)

Run the simulation defined by solver_config.

Keyword Arguments:

The value of 'adjustfinalstepis passed to the ODE solver; see [solve!](@ref ODESolvers.solve!).

The user_callbacks are passed to the ODE solver as callback functions; see solve!.

The function user_info_callback is called after the default info callback (which is called every Settings.show_updates interval). The single input argument init is true when the callback is called for initialization (before time stepping begins) and false when called during the actual ODE solve; see GenericCallbacks and solve!.

If conservation checks are to be performed, check_cons must be a tuple of ConservationCheck.

If check_euclidean_distance is true, then the Euclidean distance between the final solution and initial condition function evaluated withsolver_config.timeend` is reported.

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