firedrake.slate.static_condensation package¶
Submodules¶
firedrake.slate.static_condensation.hybridization module¶

class
firedrake.slate.static_condensation.hybridization.
HybridizationPC
[source]¶ Bases:
firedrake.slate.static_condensation.sc_base.SCBase
Create a PC context suitable for PETSc.
Matrix free preconditioners should inherit from this class and implement:
apply()
applyTranspose()

backward_substitution
(pc, y)[source]¶ Perform the backwards recovery of eliminated fields.
 Parameters
pc – a Preconditioner instance.
y – a PETSc vector for placing the resulting fields.

forward_elimination
(pc, x)[source]¶ Perform the forward elimination of fields and provide the reduced righthand side for the condensed system.
 Parameters
pc – a Preconditioner instance.
x – a PETSc vector containing the incoming righthand side.

initialize
(pc)[source]¶ Set up the problem context. Take the original mixed problem and reformulate the problem as a hybridized mixed system.
A KSP is created for the Lagrange multiplier system.

needs_python_pmat
= True¶ A Slatebased python preconditioner that solves a mixed H(div)conforming problem using hybridization. Currently, this preconditioner supports the hybridization of the RT and BDM mixed methods of arbitrary degree.
The forward eliminations and backwards reconstructions are performed elementlocal using the Slate language.

sc_solve
(pc)[source]¶ Solve the condensed linear system for the condensed field.
 Parameters
pc – a Preconditioner instance.
firedrake.slate.static_condensation.la_utils module¶

class
firedrake.slate.static_condensation.la_utils.
LAContext
¶ Bases:
tuple
Context information for systems of equations after applying algebraic transformation via Slatesupported operations. This object provides the symbolic expressions for the transformed linear system of equations.
 Parameters
lhs – The resulting expression for the transformed lefthand side matrix.
rhs – The resulting expression for the transformed righthand side vector.
field_idx – An integer or iterable of integers (if the system is mixed) denoting which field(s) the resulting solution is defined on.
Create new instance of LAContext(lhs, rhs, field_idx)

property
field_idx
¶ Alias for field number 2

property
lhs
¶ Alias for field number 0

property
rhs
¶ Alias for field number 1

firedrake.slate.static_condensation.la_utils.
backward_solve
(A, b, x, reconstruct_fields)[source]¶ Returns a sequence of linear algebra contexts containing Slate expressions for backwards substitution.
 Parameters
A – a slate.Tensor corresponding to the mixed UFL operator.
b – a firedrake.Function corresponding to the righthand side.
x – a firedrake.Function corresponding to the solution.
reconstruct_fields – a tuple of indices denoting which fields to reconstruct.

firedrake.slate.static_condensation.la_utils.
condense_and_forward_eliminate
(A, b, elim_fields)[source]¶ Returns Slate expressions for the operator and righthand side vector after eliminating specified unknowns.
 Parameters
A – a slate.Tensor corresponding to the mixed UFL operator.
b – a firedrake.Function corresponding to the righthand side.
elim_fields – a tuple of indices denoting which fields to eliminate.
firedrake.slate.static_condensation.sc_base module¶

class
firedrake.slate.static_condensation.sc_base.
SCBase
[source]¶ Bases:
firedrake.preconditioners.base.PCBase
A generalpurpose base class for static condensation interfaces.
Create a PC context suitable for PETSc.
Matrix free preconditioners should inherit from this class and implement:
initialize()
update()

apply
(pc, x, y)[source]¶ Applies the static condensation preconditioner.
 Parameters
pc – a Preconditioner instance.
x – A PETSc vector containing the incoming righthand side.
y – A PETSc vector for the result.

abstract
backward_substitution
(pc, y)[source]¶ Perform the backwards recovery of eliminated fields.
 Parameters
pc – a Preconditioner instance.
y – a PETSc vector for placing the resulting fields.

firedrake.slate.static_condensation.sc_base.
timed_region
()¶ Log.Event(type cls, name, klass=None)
firedrake.slate.static_condensation.scpc module¶

class
firedrake.slate.static_condensation.scpc.
SCPC
[source]¶ Bases:
firedrake.slate.static_condensation.sc_base.SCBase
Create a PC context suitable for PETSc.
Matrix free preconditioners should inherit from this class and implement:
apply()
applyTranspose()

backward_substitution
(pc, y)[source]¶ Perform the backwards recovery of eliminated fields.
 Parameters
pc – a Preconditioner instance.
y – a PETSc vector for placing the resulting fields.

condensed_system
(A, rhs, elim_fields)[source]¶ Forms the condensed linear system by eliminating specified unknowns.
 Parameters
A – A Slate Tensor containing the mixed bilinear form.
rhs – A firedrake function for the righthand side.
elim_fields – An iterable of field indices to eliminate.

forward_elimination
(pc, x)[source]¶ Perform the forward elimination of fields and provide the reduced righthand side for the condensed system.
 Parameters
pc – a Preconditioner instance.
x – a PETSc vector containing the incoming righthand side.

initialize
(pc)[source]¶ Set up the problem context. This takes the incoming threefield system and constructs the static condensation operators using Slate expressions.
A KSP is created for the reduced system. The eliminated variables are recovered via backsubstitution.

local_solver_calls
(A, rhs, x, elim_fields)[source]¶ Provides solver callbacks for inverting local operators and reconstructing eliminated fields.
 Parameters
A – A Slate Tensor containing the mixed bilinear form.
rhs – A firedrake function for the righthand side.
x – A firedrake function for the solution.
elim_fields – An iterable of eliminated field indices to recover.

needs_python_pmat
= True¶ A Slatebased python preconditioner implementation of static condensation for problems with up to three fields.

sc_solve
(pc)[source]¶ Solve the condensed linear system for the condensed field.
 Parameters
pc – a Preconditioner instance.