peclet::amr::AmgBottom< Dim, Bits > Class Template Reference

The agglomerated exact bottom of the pressure multigrid (docs/amr_mg_depth.md §6.6): the coarsest level's FV Laplacian assembled as the SPD matrix S = −Vol·L, with identity rows for fully closed cells and the constant nullspace projected per connected fluid component, solved by GraphAMG-preconditioned CG to relative kTol = 1e-10 (cap kMaxIters = 100). More...

#include <amg_bottom.hpp>

Public Types
using	Poisson = AmrPoisson< Dim, Bits >
	the level operator the matrix is assembled from

Public Member Functions
void	build (const Poisson &ap, bool singular)
	Assemble S from the coarsest level's AmrPoisson and build the GraphAMG hierarchy.
bool	ready () const
	True once build() has assembled a non-empty level.
bool	onDevice () const
	Whether the per-V-cycle solve runs on the device (size() > kHostMax).
Index	size () const
	Rows of the bottom matrix = cells of the coarsest level.
Index	numIdentityRows () const
	Fully closed cells (every face openness 0), solved as identity rows with solution 0.
int	numComponents () const
	Connected fluid components; each carries its own constant nullspace mode.
int	lastIters () const
	CG iterations of the last solve (0 for a zero right-hand side).
double	lastRelResidual () const
	‖rhs − S x‖∞ / ‖rhs‖∞ of the last solve, measured on the CSR the bottom itself assembled.
void	solve (View< const double > b, View< double > x) const
	x ← the solution of L x = b on the coarsest level, i.e.

Static Public Attributes
static constexpr Index	kHostMax = 10000
	Above this many rows the per-V-cycle solve runs on the device (§5.5).

Detailed Description

template<int Dim, unsigned Bits = (Dim == 2 ? 32u : (Dim == 3 ? 21u : 16u))>
class peclet::amr::AmgBottom< Dim, Bits >

The agglomerated exact bottom of the pressure multigrid (docs/amr_mg_depth.md §6.6): the coarsest level's FV Laplacian assembled as the SPD matrix S = −Vol·L, with identity rows for fully closed cells and the constant nullspace projected per connected fluid component, solved by GraphAMG-preconditioned CG to relative kTol = 1e-10 (cap kMaxIters = 100).

Owned by Multigrid (single-rank, and therefore the replicated stage's continued ladder) and by DistributedFlowMultigrid at np = 1; selected by Multigrid::setBottom — ‘Flow.set_pressure_bottom('auto’ | 'smoother' | 'agglomerated'). It changes the preconditioner, never the converged pressure. LOCAL: no MPI anywhere in the class — a replicated tail runs one identical copy per rank. Setup is host, once perbuild(); the per-V-cycle solve is host or device by size (kHostMax`). Throws nothing of its own.

Definition at line 63 of file amg_bottom.hpp.

Member Typedef Documentation

Poisson

template<int Dim, unsigned Bits = (Dim == 2 ? 32u : (Dim == 3 ? 21u : 16u))>

using peclet::amr::AmgBottom< Dim, Bits >::Poisson = AmrPoisson<Dim, Bits>

the level operator the matrix is assembled from

Definition at line 65 of file amg_bottom.hpp.

Member Function Documentation

build()

template<int Dim, unsigned Bits = (Dim == 2 ? 32u : (Dim == 3 ? 21u : 16u))>

void peclet::amr::AmgBottom< Dim, Bits >::build ( const Poisson &  ap, bool  singular  )

inline

Assemble S from the coarsest level's AmrPoisson and build the GraphAMG hierarchy.

singular = the operator has a constant nullspace per connected fluid component (the periodic pure-Neumann pressure, which is every AmrFlow path).

Definition at line 73 of file amg_bottom.hpp.

References peclet::amr::AmrPoisson< Dim, Bits >::assembleFv(), peclet::amr::AmgBottom< Dim, Bits >::kHostMax, and peclet::amr::transferFieldGradients().

ready()

template<int Dim, unsigned Bits = (Dim == 2 ? 32u : (Dim == 3 ? 21u : 16u))>

bool peclet::amr::AmgBottom< Dim, Bits >::ready ( ) const

inline

True once build() has assembled a non-empty level.

Definition at line 126 of file amg_bottom.hpp.

onDevice()

template<int Dim, unsigned Bits = (Dim == 2 ? 32u : (Dim == 3 ? 21u : 16u))>

bool peclet::amr::AmgBottom< Dim, Bits >::onDevice ( ) const

inline

Whether the per-V-cycle solve runs on the device (size() > kHostMax).

Definition at line 128 of file amg_bottom.hpp.

size()

template<int Dim, unsigned Bits = (Dim == 2 ? 32u : (Dim == 3 ? 21u : 16u))>

Index peclet::amr::AmgBottom< Dim, Bits >::size ( ) const

inline

Rows of the bottom matrix = cells of the coarsest level.

Definition at line 130 of file amg_bottom.hpp.

numIdentityRows()

template<int Dim, unsigned Bits = (Dim == 2 ? 32u : (Dim == 3 ? 21u : 16u))>

Index peclet::amr::AmgBottom< Dim, Bits >::numIdentityRows ( ) const

inline

Fully closed cells (every face openness 0), solved as identity rows with solution 0.

Definition at line 132 of file amg_bottom.hpp.

numComponents()

template<int Dim, unsigned Bits = (Dim == 2 ? 32u : (Dim == 3 ? 21u : 16u))>

int peclet::amr::AmgBottom< Dim, Bits >::numComponents ( ) const

inline

Connected fluid components; each carries its own constant nullspace mode.

Definition at line 134 of file amg_bottom.hpp.

lastIters()

template<int Dim, unsigned Bits = (Dim == 2 ? 32u : (Dim == 3 ? 21u : 16u))>

int peclet::amr::AmgBottom< Dim, Bits >::lastIters ( ) const

inline

CG iterations of the last solve (0 for a zero right-hand side).

Definition at line 136 of file amg_bottom.hpp.

lastRelResidual()

template<int Dim, unsigned Bits = (Dim == 2 ? 32u : (Dim == 3 ? 21u : 16u))>

double peclet::amr::AmgBottom< Dim, Bits >::lastRelResidual ( ) const

inline

‖rhs − S x‖∞ / ‖rhs‖∞ of the last solve, measured on the CSR the bottom itself assembled.

The V-cycle's own FvOp check (the §6.6 consistency gate) lives in Multigrid::vcycle and is the one §10 quotes.

Definition at line 140 of file amg_bottom.hpp.

solve()

template<int Dim, unsigned Bits = (Dim == 2 ? 32u : (Dim == 3 ? 21u : 16u))>

void peclet::amr::AmgBottom< Dim, Bits >::solve ( View< const double >  b, View< double >  x  ) const

inline

x ← the solution of L x = b on the coarsest level, i.e.

S x = −b/invVol, projected onto the complement of the per-component nullspace. Device views, which may be LONGER than size() (the distributed levels carry a ghost tail); only the first size() rows are read and written, and everything runs through this class's own scratch so a subview is never needed.

Definition at line 146 of file amg_bottom.hpp.

References peclet::amr::transferFieldGradients().

Member Data Documentation

kHostMax

template<int Dim, unsigned Bits = (Dim == 2 ? 32u : (Dim == 3 ? 21u : 16u))>

constexpr Index peclet::amr::AmgBottom< Dim, Bits >::kHostMax = 10000

staticconstexpr

Above this many rows the per-V-cycle solve runs on the device (§5.5).

Definition at line 68 of file amg_bottom.hpp.

Referenced by peclet::amr::AmgBottom< Dim, Bits >::build().

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The documentation for this class was generated from the following file:

• amg_bottom.hpp