desc.objectives.VacuumBoundaryError

class desc.objectives.VacuumBoundaryError(eq, field, target=None, bounds=None, weight=1, normalize=True, normalize_target=True, loss_function=None, deriv_mode='auto', grid=None, field_grid=None, field_fixed=False, name='Vacuum boundary error')Source

Target for free boundary conditions on LCFS for vacuum equilibrium.

Computes the residuals of the following:

𝐁ₒᵤₜ ⋅ 𝐧 = 0 𝐁ₒᵤₜ² - 𝐁ᵢₙ² = 0

Where 𝐁ᵢₙ is the total field inside the LCFS (from fixed boundary calculation) 𝐁ₒᵤₜ is the total field outside the LCFS (from coils), and 𝐧 is the outward surface normal. All residuals are weighted by the local area element ||𝐞_θ × 𝐞_ζ|| Δθ Δζ

(Technically for vacuum equilibria the second condition is redundant with the first, but including it makes things more robust).

Parameters:

• eq (Equilibrium) – Equilibrium that will be optimized to satisfy the Objective.

• field (MagneticField) – External field produced by coils or other sources outside the plasma.

• target (float, ndarray, optional) – Target value(s) of the objective. Only used if bounds is None. len(target) must be equal to Objective.dim_f

• bounds (tuple, optional) – Lower and upper bounds on the objective. Overrides target. len(bounds[0]) and len(bounds[1]) must be equal to Objective.dim_f

• weight (float, ndarray, optional) – Weighting to apply to the Objective, relative to other Objectives. len(weight) must be equal to Objective.dim_f

• normalize (bool) – Whether to compute the error in physical units or non-dimensionalize.

• normalize_target (bool) – Whether target and bounds should be normalized before comparing to computed values. If normalize is True and the target is in physical units, this should also be set to True.

• loss_function ({None, 'mean', 'min', 'max'}, optional) – Loss function to apply to the objective values once computed. This loss function is called on the raw compute value, before any shifting, scaling, or normalization.

• deriv_mode ({"auto", "fwd", "rev"}) – Specify how to compute jacobian matrix, either forward mode or reverse mode AD. “auto” selects forward or reverse mode based on the size of the input and output of the objective. Has no effect on self.grad or self.hess which always use reverse mode and forward over reverse mode respectively.

• grid (Grid, optional) – Collocation grid containing the nodes to evaluate error at. Should be at rho=1.

• field_grid (Grid, optional) – Grid used to discretize field.

• field_fixed (bool) – Whether to assume the field is fixed. For free boundary solve, should be fixed. For single stage optimization, should be False (default).

• name (str) – Name of the objective function.

Methods

build([use_jit, verbose])	Build constant arrays.
compute(eq_params[, field_params, constants])	Compute boundary force error.
compute_scalar(*args, **kwargs)	Compute the scalar form of the objective.
compute_scaled(*args, **kwargs)	Compute and apply weighting and normalization.
compute_scaled_error(*args, **kwargs)	Compute and apply the target/bounds, weighting, and normalization.
compute_unscaled(*args, **kwargs)	Compute the raw value of the objective.
copy([deepcopy])	Return a (deep)copy of this object.
equiv(other)	Compare equivalence between DESC objects.
grad(*args, **kwargs)	Compute gradient vector of self.compute_scalar wrt x.
hess(*args, **kwargs)	Compute Hessian matrix of self.compute_scalar wrt x.
jac_scaled(*args, **kwargs)	Compute Jacobian matrix of self.compute_scaled wrt x.
jac_scaled_error(*args, **kwargs)	Compute Jacobian matrix of self.compute_scaled_error wrt x.
jac_unscaled(*args, **kwargs)	Compute Jacobian matrix of self.compute_unscaled wrt x.
jit()	Apply JIT to compute methods, or re-apply after updating self.
jvp_scaled(v, x[, constants])	Compute Jacobian-vector product of self.compute_scaled.
jvp_scaled_error(v, x[, constants])	Compute Jacobian-vector product of self.compute_scaled_error.
jvp_unscaled(v, x[, constants])	Compute Jacobian-vector product of self.compute_unscaled.
load(load_from[, file_format])	Initialize from file.
print_value(*args, **kwargs)	Print the value of the objective.
save(file_name[, file_format, file_mode])	Save the object.
xs(*things)	Return a tuple of args required by this objective from optimizable things.

Attributes

bounds	Lower and upper bounds of the objective.
built	Whether the transforms have been precomputed (or not).
constants	Constant parameters such as transforms and profiles.
dim_f	Number of objective equations.
fixed	Whether the objective fixes individual parameters (or linear combo).
linear	Whether the objective is a linear function (or nonlinear).
name	Name of objective (str).
normalization	normalizing scale factor.
scalar	Whether default "compute" method is a scalar or vector.
target	Target value(s) of the objective.
things	Optimizable things that this objective is tied to.
weight	Weighting to apply to the Objective, relative to other Objectives.