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Commented declaremodule and modulesynopsis.


 1 2 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 3 % 4 % Copyright (c) 2003-2010 by University of Queensland 5 % Earth Systems Science Computational Center (ESSCC) 6 7 % 8 % Primary Business: Queensland, Australia 9 % Licensed under the Open Software License version 3.0 10 11 % 12 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 13 14 15 \chapter{The \linearPDEs Module} 16 17 \section{Linear Partial Differential Equations} 18 \label{SEC LinearPDE} 19 20 The \LinearPDE class is used to define a general linear, steady, second order PDE 21 for an unknown function $u$ on a given $\Omega$ defined through a \Domain object. 22 In the following $\Gamma$ denotes the boundary of the domain $\Omega$. $n$ denotes 23 the outer normal field on $\Gamma$. 24 25 For a single PDE with a solution with a single component the linear PDE is defined in the 26 following form: 27 \begin{equation}\label{LINEARPDE.SINGLE.1} 28 -(A_{jl} u_{,l})_{,j}-(B_{j} u)_{,j}+C_{l} u_{,l}+D u =-X_{j,j}+Y \; . 29 \end{equation} 30 $u_{,j}$ denotes the derivative of $u$ with respect to the $j$-th spatial direction. Einstein's summation convention, ie. summation over indexes appearing twice in a term of a sum is performed, is used. 31 The coefficients $A$, $B$, $C$, $D$, $X$ and $Y$ have to be specified through \Data objects in the 32 \Function on the PDE or objects that can be converted into such \Data objects. 33 $A$ is a \RankTwo, $B$, $C$ and $X$ are \RankOne and $D$ and $Y$ are scalar. 34 The following natural 35 boundary conditions are considered \index{boundary condition!natural} on $\Gamma$: 36 \begin{equation}\label{LINEARPDE.SINGLE.2} 37 n_{j}(A_{jl} u_{,l}+B_{j} u)+d u=n_{j}X_{j} + y \;. 38 \end{equation} 39 Notice that the coefficients $A$, $B$ and $X$ are defined in the PDE. The coefficients $d$ and $y$ are 40 each a \Scalar in the \FunctionOnBoundary. Constraints \index{constraint} for the solution prescribing the value of the 41 solution at certain locations in the domain. They have the form 42 \begin{equation}\label{LINEARPDE.SINGLE.3} 43 u=r \mbox{ where } q>0 44 \end{equation} 45 $r$ and $q$ are each \Scalar where $q$ is the characteristic function 46 \index{characteristic function} defining where the constraint is applied. 47 The constraints defined by \eqn{LINEARPDE.SINGLE.3} override any other condition set by \eqn{LINEARPDE.SINGLE.1} 48 or \eqn{LINEARPDE.SINGLE.2}. 49 50 For a system of PDEs and a solution with several components the PDE has the form 51 \begin{equation}\label{LINEARPDE.SYSTEM.1} 52 -(A_{ijkl} u_{k,l})_{,j}-(B_{ijk} u_{k})_{,j}+C_{ikl} u_{k,l}+D_{ik} u_{k} =-X_{ij,j}+Y_{i} \; . 53 \end{equation} 54 $A$ is a \RankFour, $B$ and $C$ are each a \RankThree, $D$ and $X$ are each a \RankTwo and $Y$ is a \RankOne. 55 The natural boundary conditions \index{boundary condition!natural} take the form: 56 \begin{equation}\label{LINEARPDE.SYSTEM.2} 57 n_{j}(A_{ijkl} u_{k,l}+B_{ijk} u_{k})+d_{ik} u_{k}=n_{j}X_{ij}+y_{i} \;. 58 \end{equation} 59 The coefficient $d$ is a \RankTwo and $y$ is a 60 \RankOne both in the \FunctionOnBoundary. Constraints \index{constraint} take the form 61 \begin{equation}\label{LINEARPDE.SYSTEM.3} 62 u_{i}=r_{i} \mbox{ where } q_{i}>0 63 \end{equation} 64 $r$ and $q$ are each \RankOne. Notice that not necessarily all components must 65 have a constraint at all locations. 66 67 \LinearPDE also supports solution discontinuities \index{discontinuity} over contact region $\Gamma^{contact}$ 68 in the domain $\Omega$. To specify the conditions across the discontinuity we are using the 69 generalised flux $J$\footnote{In some applications the definition of flux used here can be different from the commonly used definition. For instance, if $T$ is a temperature field the heat flux $q$ is defined as $q_{,i}=-\kappa T_{,i}$ ($\kappa$ is diffusifity) which differs from the definition used here by the sign. This needs to be kept in mind when defining natural boundary conditions.\index{boundary condition!natural}} which is in the case of a systems of PDEs and several components of the solution 70 defined as 71 \begin{equation}\label{LINEARPDE.SYSTEM.5} 72 J_{ij}=A_{ijkl}u_{k,l}+B_{ijk}u_{k}-X_{ij} 73 \end{equation} 74 For the case of single solution component and single PDE $J$ is defined 75 \begin{equation}\label{LINEARPDE.SINGLE.5} 76 J_{j}=A_{jl}u_{,l}+B_{j}u_{k}-X_{j} 77 \end{equation} 78 In the context of discontinuities \index{discontinuity} $n$ denotes the normal on the 79 discontinuity pointing from side 0 towards side 1. For a system of PDEs 80 the contact condition takes the form 81 \begin{equation}\label{LINEARPDE.SYSTEM.6} 82 n_{j} J^{0}_{ij}=n_{j} J^{1}_{ij}=y^{contact}_{i} - d^{contact}_{ik} [u]_{k} \; . 83 \end{equation} 84 where $J^{0}$ and $J^{1}$ are the fluxes on side $0$ and side $1$ of the 85 discontinuity $\Gamma^{contact}$, respectively. $[u]$, which is the difference 86 of the solution at side 1 and at side 0, denotes the jump of $u$ across $\Gamma^{contact}$. 87 The coefficient $d^{contact}$ is a \RankTwo and $y^{contact}$ is a 88 \RankOne both in the \FunctionOnContactZero or \FunctionOnContactOne. 89 In case of a single PDE and a single component solution the contact condition takes the form 90 \begin{equation}\label{LINEARPDE.SINGLE.6} 91 n_{j} J^{0}_{j}=n_{j} J^{1}_{j}=y^{contact} - d^{contact}[u] 92 \end{equation} 93 In this case the the coefficient $d^{contact}$ and $y^{contact}$ are each \Scalar 94 both in the \FunctionOnContactZero or \FunctionOnContactOne. 95 96 The PDE is symmetrical \index{symmetrical} if 97 \begin{equation}\label{LINEARPDE.SINGLE.4} 98 A_{jl}=A_{lj} \mbox{ and } B_{j}=C_{j} 99 \end{equation} 100 The system of PDEs is symmetrical \index{symmetrical} if 101 \begin{eqnarray} 102 \label{LINEARPDE.SYSTEM.4} 103 A_{ijkl}&=&A_{klij} \\ 104 B_{ijk}&=&C_{kij} \\ 105 D_{ik}&=&D_{ki} \\ 106 d_{ik}&=&d_{ki} \\ 107 d^{contact}_{ik}&=&d^{contact}_{ki} 108 \end{eqnarray} 109 Note that in contrast with the scalar case~\eqn{LINEARPDE.SINGLE.4} now the coefficients $D$, $d$ abd $d^{contact}$ 110 have to be inspected. 111 112 The following example illustrates the typical usage of the \LinearPDE class: 113 \begin{python} 114 from esys.escript import * 115 from esys.escript.linearPDEs import LinearPDE 116 from esys.finley import Rectangle 117 mydomain = Rectangle(l0=1.,l1=1.,n0=40, n1=20) 118 mypde=LinearPDE(mydomain) 119 mypde.setSymmetryOn() 120 mypde.setValue(A=kappa*kronecker(mydomain),D=1,Y=1) 121 u=mypde.getSolution() 122 \end{python} 123 We refer to chapter~\ref{CHAP: Tutorial} for more details. 124 125 An instance of the \SolverOptions class is attached to the \LinearPDE class object. It is used to set options of the solver used to solve the PDE. In the following 126 code the \method{getSolverOptions} is used to access the \SolverOptions 127 attached to \var{mypde}: 128 \begin{python} 129 from esys.escript import * 130 from esys.escript.linearPDEs import LinearPDE, SolverOptions 131 from esys.finley import Rectangle 132 mydomain = Rectangle(l0=1.,l1=1.,n0=40, n1=20) 133 mypde=LinearPDE(mydomain) 134 mypde.setValue(A=kappa*kronecker(mydomain),D=1,Y=1) 135 mypde.getSolverOptions().setVerbosityOn() 136 mypde.getSolverOptions().setSolverMethod(SolverOptions.PCG) 137 mypde.getSolverOptions().setPreconditioner(SolverOptions.AMG) 138 mypde.getSolverOptions().setTolerance(1e-8) 139 mypde.getSolverOptions().setIterMax(1000) 140 u=mypde.getSolution() 141 \end{python} 142 In this example, the preconditioned conjugate gradient method \PCG is used 143 with preconditioner \AMG. The relative tolerance is set to $10^{-8}$ and 144 the maximum number of iteration steps to $1000$. 145 After a completed solution call, 146 the attached \SolverOptions object gives access to diagnostic informations: 147 \begin{python} 148 u=mypde.getSolution() 149 print 'Number of iteration steps =', mypde.getDiagnostics('num_iter') 150 print 'Total solution time =', mypde.getDiagnostics('time') 151 print 'Set-up time =', mypde.getDiagnostics('set_up_time') 152 print 'Net time =', mypde.getDiagnostics('net_time') 153 print 'Residual norm of returned solution =', mypde.getDiagnostics('residual_norm') 154 \end{python} 155 Typically a negative value for a diagnostic value indicates that the value is undefined. 156 157 \subsection{Classes} 158 %\declaremodule{extension}{esys.escript.linearPDEs} 159 %\modulesynopsis{Linear partial differential equation handler} 160 The module \linearPDEs provides an interface to define and solve linear partial 161 differential equations within \escript. The module \linearPDEs does not provide any 162 solver capabilities in itself but hands the PDE over to 163 the PDE solver library defined through the \Domain of the PDE, eg. \finley. 164 The general interface is provided through the \LinearPDE class. The \Poisson 165 class which is also derived form the \LinearPDE class should be used 166 to define the Poisson equation \index{Poisson}. 167 168 \subsection{\LinearPDE class} 169 This is the general class to define a linear PDE in \escript. We list a selection of the most 170 important methods of the class. For a complete list, see the reference at \ReferenceGuide. 171 172 \begin{classdesc}{LinearPDE}{domain,numEquations=0,numSolutions=0} 173 opens a linear, steady, second order PDE on the \Domain \var{domain}. The parameters \var{numEquations} 174 and \var{numSolutions} give the number of equations and the number of solution components. 175 If \var{numEquations} and \var{numSolutions} are non-positive, then the number of equations 176 and the number solutions, respectively, stay undefined until a coefficient is 177 defined. 178 \end{classdesc} 179 180 \subsubsection{\LinearPDE methods} 181 182 \begin{methoddesc}[LinearPDE]{setValue}{ 183 \optional{A}\optional{, B}, 184 \optional{, C}\optional{, D} 185 \optional{, X}\optional{, Y} 186 \optional{, d}\optional{, y} 187 \optional{, d_contact}\optional{, y_contact} 188 \optional{, q}\optional{, r}} 189 assigns new values to coefficients. By default all values are assumed to be zero\footnote{ 190 In fact it is assumed they are not present by assigning the value \code{escript.Data()}. The 191 can by used by the solver library to reduce computational costs. 192 } 193 If the new coefficient value is not a \Data object, it is converted into a \Data object in the 194 appropriate \FunctionSpace. 195 \end{methoddesc} 196 197 \begin{methoddesc}[LinearPDE]{getCoefficient}{name} 198 return the value assigned to coefficient \var{name}. If \var{name} is not a valid name 199 an exception is raised. 200 \end{methoddesc} 201 202 \begin{methoddesc}[LinearPDE]{getShapeOfCoefficient}{name} 203 returns the shape of coefficient \var{name} even if no value has been assigned to it. 204 \end{methoddesc} 205 206 \begin{methoddesc}[LinearPDE]{getFunctionSpaceForCoefficient}{name} 207 returns the \FunctionSpace of coefficient \var{name} even if no value has been assigned to it. 208 \end{methoddesc} 209 210 \begin{methoddesc}[LinearPDE]{setDebugOn}{} 211 switches on debug mode. 212 \end{methoddesc} 213 214 \begin{methoddesc}[LinearPDE]{setDebugOff}{} 215 switches off debug mode. 216 \end{methoddesc} 217 218 \begin{methoddesc}[LinearPDE]{getSolverOptions}{} 219 returns the solver options for solving the PDE. In fact the method returns 220 a \SolverOptions class object which can be used to modify the tolerance, 221 the solver or the preconditioner, see Section~\ref{SEC Solver Options} for details. 222 \end{methoddesc} 223 224 \begin{methoddesc}[LinearPDE]{setSolverOptions}{\optional{options=None}} 225 sets the solver options for solving the PDE. If argument \var{options} is present it 226 must be a \SolverOptions class object, see Section~\ref{SEC Solver Options} for details. Otherwise the solver options are reset to the default. 227 \end{methoddesc} 228 229 230 \begin{methoddesc}[LinearPDE]{isUsingLumping}{} 231 returns \True if \LUMPING is set as the solver for the system of linear equations. 232 Otherwise \False is returned. 233 \end{methoddesc} 234 235 236 \begin{methoddesc}[LinearPDE]{getDomain}{} 237 returns the \Domain of the PDE. 238 \end{methoddesc} 239 240 \begin{methoddesc}[LinearPDE]{getDim}{} 241 returns the spatial dimension of the PDE. 242 \end{methoddesc} 243 244 \begin{methoddesc}[LinearPDE]{getNumEquations}{} 245 returns the number of equations. 246 \end{methoddesc} 247 248 \begin{methoddesc}[LinearPDE]{getNumSolutions}{} 249 returns the number of components of the solution. 250 \end{methoddesc} 251 252 \begin{methoddesc}[LinearPDE]{checkSymmetry}{verbose=\False} 253 returns \True if the PDE is symmetric and \False otherwise. 254 The method is very computationally expensive and should only be 255 called for testing purposes. The symmetry flag is not altered. 256 If \var{verbose}=\True information about where symmetry is violated 257 are printed. 258 \end{methoddesc} 259 260 \begin{methoddesc}[LinearPDE]{getFlux}{u} 261 returns the flux $J_{ij}$ \index{flux} for given solution \var{u} 262 defined by \eqn{LINEARPDE.SYSTEM.5} and \eqn{LINEARPDE.SINGLE.5}, respectively. 263 \end{methoddesc} 264 265 266 \begin{methoddesc}[LinearPDE]{isSymmetric}{} 267 returns \True if the PDE has been indicated to be symmetric. 268 Otherwise \False is returned. 269 \end{methoddesc} 270 271 \begin{methoddesc}[LinearPDE]{setSymmetryOn}{} 272 indicates that the PDE is symmetric. 273 \end{methoddesc} 274 275 \begin{methoddesc}[LinearPDE]{setSymmetryOff}{} 276 indicates that the PDE is not symmetric. 277 \end{methoddesc} 278 279 \begin{methoddesc}[LinearPDE]{setReducedOrderOn}{} 280 switches on the reduction of polynomial order for the solution and equation evaluation even if 281 a quadratic or higher interpolation order is defined in the \Domain. This feature may not 282 be supported by all PDE libraries. 283 \end{methoddesc} 284 285 \begin{methoddesc}[LinearPDE]{setReducedOrderOff}{} 286 switches off the reduction of polynomial order for the solution and 287 equation evaluation. 288 \end{methoddesc} 289 290 \begin{methoddesc}[LinearPDE]{getOperator}{} 291 returns the \Operator of the PDE. 292 \end{methoddesc} 293 294 \begin{methoddesc}[LinearPDE]{getRightHandSide}{} 295 returns the right hand side of the PDE as a \Data object. If 296 \var{ignoreConstraint}=\True, then the constraints are not considered 297 when building up the right hand side. 298 \end{methoddesc} 299 300 \begin{methoddesc}[LinearPDE]{getSystem}{} 301 returns the \Operator and right hand side of the PDE. 302 \end{methoddesc} 303 304 \begin{methoddesc}[LinearPDE]{getSolution}{} 305 returns (an approximation of) the solution of the PDE. This call 306 will invoke the discretization of the PDE and the solution of the resulting 307 system of linear equations. Keep in mind that this call is typically computational 308 expensive and can - depending on the PDE and the discretiztion - take a long time to complete. 309 \end{methoddesc} 310 311 312 313 \subsection{The \Poisson Class} 314 The \Poisson class provides an easy way to define and solve the Poisson 315 equation 316 \begin{equation}\label{POISSON.1} 317 -u_{,ii}=f\; . 318 \end{equation} 319 with homogeneous boundary conditions 320 \begin{equation}\label{POISSON.2} 321 n_{i}u_{,i}=0 322 \end{equation} 323 and homogeneous constraints 324 \begin{equation}\label{POISSON.3} 325 u=0 \mbox{ where } q>0 326 \end{equation} 327 $f$ has to be a \Scalar in the \Function and $q$ must be 328 a \Scalar in the \SolutionFS. 329 330 \begin{classdesc}{Poisson}{domain} 331 opens a Poisson equation on the \Domain domain. \Poisson is derived from \LinearPDE. 332 \end{classdesc} 333 \begin{methoddesc}[Poisson]{setValue}{f=escript.Data(),q=escript.Data()} 334 assigns new values to \var{f} and \var{q}. 335 \end{methoddesc} 336 337 \subsection{The \Helmholtz Class} 338 The \Helmholtz class defines the Helmholtz problem 339 \begin{equation}\label{HZ.1} 340 \omega \; u - (k\; u_{,j})_{,j} = f 341 \end{equation} 342 with natural boundary conditions 343 \begin{equation}\label{HZ.2} 344 k\; u_{,j} n_{,j} = g- \alpha \; u 345 \end{equation} 346 and constraints: 347 \begin{equation}\label{HZ.3} 348 u=r \mbox{ where } q>0 349 \end{equation} 350 $\omega$, $k$, $f$ have to be a \Scalar in the \Function, 351 $g$ and $\alpha$ must be a \Scalar in the \FunctionOnBoundary, 352 and $q$ and $r$ must be a \Scalar in the \SolutionFS or must be mapped or interpolated into the particular \FunctionSpace. 353 354 \begin{classdesc}{Helmholtz}{domain} 355 opens a Helmholtz equation on the \Domain domain. \Helmholtz is derived from \LinearPDE. 356 \end{classdesc} 357 \begin{methoddesc}[Helmholtz]{setValue}{ \optional{omega} \optional{, k} \optional{, f} \optional{, alpha} \optional{, g} \optional{, r} \optional{, q}} 358 assigns new values to \var{omega}, \var{k}, \var{f}, \var{alpha}, \var{g}, \var{r}, \var{q}. By default all values are set to be zero. 359 \end{methoddesc} 360 361 \subsection{The \Lame Class} 362 The \Lame class defines a Lame equation problem: 363 \begin{equation}\label{LE.1} 364 -(\mu (u_{i,j}+u_{j,i})+\lambda u_{k,k}\delta_{ij})_{j} = F_{i}-\sigma_{ij,j} 365 \end{equation} 366 with natural boundary conditions: 367 \begin{equation}\label{LE.2} 368 n_{j}(\mu \; (u_{i,j}+u_{j,i})+\lambda u_{k,k}\delta_{ij}) = f_{i}+n_{j}\sigma_{ij} 369 \end{equation} 370 and constraint 371 \begin{equation}\label{LE.3} 372 u_{i}=r_{i} \mbox{ where } q_{i}>0 373 \end{equation} 374 $\mu$, $\lambda$ have to be a \Scalar in the \Function, 375 $F$ has to be a \Vector in the \Function, 376 $\sigma$ has to be a \Tensor in the \Function, 377 $f$ must be a \Vector in the \FunctionOnBoundary, 378 and $q$ and $r$ must be a \Vector in the \SolutionFS or must be mapped or interpolated into the particular \FunctionSpace. 379 380 \begin{classdesc}{Lame}{domain} 381 opens a Lame equation on the \Domain domain. \Lame is derived from \LinearPDE. 382 \end{classdesc} 383 \begin{methoddesc}[Lame]{setValue}{ \optional{lame_lambda} \optional{, lame_mu} \optional{, F} \optional{, sigma} \optional{, f} \optional{, r} \optional{, q}} 384 assigns new values to 385 \var{lame_lambda}, 386 \var{lame_mu}, 387 \var{F}, 388 \var{sigma}, 389 \var{f}, 390 \var{r} and 391 \var{q} 392 By default all values are set to be zero. 393 \end{methoddesc} 394 395 396 397 \section{Projection} 398 %\declaremodule{extension}{esys.escript.pdetools} 399 \label{SEC Projection} 400 401 Using the \LinearPDE class provides an option to change the \FunctionSpace attribute in addition 402 to the standard interpolation mechanism\index{interpolation} as 403 discussed on in Chapter~\ref{ESCRIPT CHAP}. If one looks the 404 stripped down version 405 \begin{equation}\label{PROJ.1} 406 u = Y 407 \end{equation} 408 of the general scalar PDE~\ref{LINEARPDE.SINGLE.1} (boundary conditions are irrelevant) 409 one can see the solution $u$ of this PDE as a project of the input function $Y$ 410 which has the \Function attribute to a function with the \SolutionFS or \ReducedSolutionFS 411 attribute. In fact, the solution maps values defined at 412 element centers representing a possibly discontinuous function 413 onto a continuous function represented by its values at the nodes of the FEM mesh. 414 This mapping is called a projection\index{projection}. Projection 415 can be a useful tool but needs to be applied with some care due to the fact that 416 a potentially discontinuous function is projected onto a continuous function but it can 417 also be a desirable effect for instance to smooth a function. The projection of the 418 gradient of a function typically calculated on the element center to the 419 nodes of a FEM mesh can be evaluated on the domain boundary and so projection provides a tool to extrapolate 420 the gradient from the internal to the boundary. This is only a reasonable procedure in the absence of singularities at the boundary. 421 422 As projection is used often in simulations \escript provides an easy to use class \class{Projector} 423 which is part of the \pdetools module. The following script demonstrates 424 the usage of the class to project the piecewise constant function ($=1$ for $x_{0}\ge 0.5$ and 425 $=-1$ for $x_{0}<0.5$ ) to a function with the \ReducedSolutionFS attribute (default target) 426 \begin{python} 427 from esys.escript.pdetools import Projector 428 proj=Projector(domain) 429 x0=domain.getX() 430 jmp=1.-2.*wherePositive(x0-0.5) 431 u=proj.getValue(jmp) 432 # alternative call: 433 u=proj(jmp) 434 \end{python} 435 By default the class uses lumping to solve the PDE~\ref{PROJ.1}. This technique is faster 436 then using the standard solver techniques of PDEs. In essence it leads to using the average of 437 neighbor element values to calculate the value at each FEM node. 438 439 The following script illustrate how to evaluate the normal stress 440 on the boundary from a given displacement field \var{u}: 441 \begin{python} 442 from esys.escript.pdetools import Projector 443 u=... 444 proj=Projector(u.getDomin()) 445 e=symmetric(grad(u)) 446 stress = G*e+ (K-2./3.*G)*trace(e)*kronecker(u.getDomin()) 447 normal_stress = inner(u.getDomin().getNormal(), proj(stress)) 448 \end{python} 449 450 451 452 \begin{classdesc}{Projector}{domain\optional{, reduce=\True \optional{, fast=\True}}} 453 This class defines the projector on the domain \var{domain}. 454 If \var{reduce} is set to \True the projection will be returned 455 as a \ReducedSolutionFS \Data object. Otherwise \SolutionFS representation is returned. 456 If \var{reduce} is set to \True lumping is used when 457 the equation~\ref{PROJ.1} is solved. Otherwise the standard 458 PDE solver is used. Notice, that lumping is requires significant less 459 compute time and memory. The class is callable. 460 \end{classdesc} 461 462 \begin{methoddesc}[Projector]{getSolverOptions}{} 463 returns the solver options for solving the PDE. In fact the method returns 464 a \SolverOptions class object which can be used to modify the tolerance, 465 the solver or the preconditioner, see Section~\ref{SEC Solver Options} for details. 466 \end{methoddesc} 467 468 \begin{methoddesc}[Projector]{getValue}{input_data} 469 projects the \var{input_data}. This method is equivalent to call an instance 470 of the class with argument \var{input_data}: 471 472 \end{methoddesc} 473 474 475 % \section{Transport Problems} 476 % \label{SEC Transport} 477 478 \section{Solver Options} 479 \label{SEC Solver Options} 480 481 \begin{classdesc}{SolverOptions}{} 482 This class defines the solver options for a linear or non-linear solver. 483 The option also supports the handling of diagnostic informations. 484 \end{classdesc} 485 486 \begin{methoddesc}[SolverOptions]{getSummary}{} 487 Returns a string reporting the current settings 488 \end{methoddesc} 489 490 \begin{methoddesc}[SolverOptions]{getName}{key} 491 Returns the name as a string of a given key 492 \end{methoddesc} 493 494 \begin{methoddesc}[SolverOptions]{setSolverMethod}{\optional{method=SolverOptions.DEFAULT}} 495 Sets the solver method to be used. Use \var{method}=\member{SolverOptions.DIRECT} to indicate that a direct rather than an iterative solver should be used and use \var{method}=\member{SolverOptions.ITERATIVE} to indicate that an iterative rather than a direct solver should be used. 496 The value of \var{method} must be one of the constants:\\ 497 \member{SolverOptions.DEFAULT}\\ \member{SolverOptions.DIRECT}\\ \member{SolverOptions.CHOLEVSKY}\\ 498 \member{SolverOptions.PCG}\\\member{SolverOptions.CR}\\ \member{SolverOptions.CGS}\\ \member{SolverOptions.BICGSTAB}\\ 499 \member{SolverOptions.SSOR}\\ 500 \member{SolverOptions.GMRES}\\ \member{SolverOptions.PRES20}\\ \member{SolverOptions.LUMPING}\\ \member{SolverOptions.ITERATIVE}\\ 501 \member{SolverOptions.NONLINEAR_GMRES}\\ \member{SolverOptions.TFQMR}\\ \member{SolverOptions.MINRES}\\ 502 \member{SolverOptions.GAUSS_SEIDEL}.\\ 503 Not all packages support all solvers. It can be assumed that a package makes a reasonable choice if it encounters. See Table~\ref{TAB FINLEY SOLVER OPTIONS 1} for the solvers supported by \finley. 504 \end{methoddesc} 505 506 \begin{methoddesc}[SolverOptions]{getSolverMethod}{} 507 Returns key of the solver method to be used. 508 \end{methoddesc} 509 510 \begin{methoddesc}[SolverOptions]{setPreconditioner}{\optional{preconditioner=SolverOptions.JACOBI}} 511 Sets the preconditioner to be used. 512 The value of \var{preconditioner} must be one of the constants:\\ 513 \member{SolverOptions.ILU0}\\ \member{SolverOptions.ILUT}\\ \member{SolverOptions.JACOBI}\\ 514 \member{SolverOptions.AMG}\\ \member{SolverOptions.REC_ILU}\\ \member{SolverOptions.GAUSS_SEIDEL}\\ \member{SolverOptions.RILU}\\ 515 \member{SolverOptions.NO_PRECONDITIONER}.\\ 516 Not all packages support all preconditioner. It can be assumed that a package makes a reasonable choice if it encounters 517 an unknown preconditioner. See Table~\ref{TAB FINLEY SOLVER OPTIONS 2} for the solvers supported by \finley. 518 \end{methoddesc} 519 520 \begin{methoddesc}[SolverOptions]{getPreconditioner}{} 521 Returns key of the preconditioner to be used. 522 \end{methoddesc} 523 524 \begin{methoddesc}[SolverOptions]{setPackage}{\optional{package=SolverOptions.DEFAULT}} 525 Sets the solver package to be used as a solver. 526 The value of \var{method} must be one of the constants:\\ 527 \member{SolverOptions.DEFAULT}\\ 528 \member{SolverOptions.PASO}\\ 529 \member{SolverOptions.SUPER_LU}\\ 530 \member{SolverOptions.PASTIX}\\ 531 \member{SolverOptions.MKL}\\ 532 \member{SolverOptions.UMFPACK}\\ 533 \member{SolverOptions.TRILINOS}.\\ 534 Not all packages are supported on all implementation. An exception may be thrown on some platforms if a particular package is requested. Currently \finley supports \member{SolverOptions.PASO} (as default) 535 and, if available, \member{SolverOptions.MKL} 536 \footnote{If the stiffness matrix is non-regular \MKL may return without 537 returning a proper error code. If you observe suspicious solutions when using MKL, this may cause by a non-invertible operator. } 538 and \member{SolverOptions.UMFPACK} 539 540 \end{methoddesc} 541 542 \begin{methoddesc}[SolverOptions]{getPackage}{} 543 Returns the solver package key 544 \end{methoddesc} 545 546 547 \begin{methoddesc}[SolverOptions]{resetDiagnostics}{\optional{all=False}} 548 resets the diagnostics. If \var{all} is \True all diagnostics including accumulative counters are reset. 549 \end{methoddesc} 550 551 \begin{methoddesc}[SolverOptions]{getDiagnostics}{\optional{ name}} 552 Returns the diagnostic information \var{name}. The following keywords are 553 supported: 554 \begin{itemize} 555 \item "num_iter": the number of iteration steps 556 \item "cum_num_iter": the cumulative number of iteration steps 557 \item "num_level": the number of level in multi level solver 558 \item "num_inner_iter": the number of inner iteration steps 559 \item"cum_num_inner_iter": the cumulative number of inner iteration steps 560 \item"time": execution time 561 \item "cum_time": cumulative execution time 562 \item "set_up_time": time to set up of the solver, typically this includes factorization and reordering 563 \item "cum_set_up_time": cumulative time to set up of the solver 564 \item "net_time": net execution time, excluding setup time for the solver and execution time for preconditioner 565 \item "cum_net_time": cumulative net execution time 566 \item "residual_norm": norm of the final residual 567 \item "converged": status of convergence 568 \item "preconditioner_size": size of precondtioner in Mbytes. 569 \end{itemize} 570 \end{methoddesc} 571 572 573 \begin{methoddesc}[SolverOptions]{hasConverged}{} 574 Returns \True if the last solver call has been finalized successfully. 575 If an exception has been thrown by the solver the status of this flag is undefined. 576 \end{methoddesc} 577 578 \begin{methoddesc}[SolverOptions]{setCoarsening}{\optional{method=SolverOptions.DEFAULT}} 579 Sets the key of the coarsening method to be applied in \AMG. 580 The value of \var{method} must be one of the constants:\\ 581 \member{SolverOptions.DEFAULT}\\ 582 \member{SolverOptions.STANDARD_COARSENING}\\ 583 \member{SolverOptions.YAIR_SHAPIRA_COARSENING}, \\ 584 \member{SolverOptions.RUGE_STUEBEN_COARSENING}~\footnote{The Ruge-Stueben and aggregation coarsening algorithms used for measuring the strength of connection only, but splitting is done with greedy algorithm.}, \\ \member{SolverOptions.AGGREGATION_COARSENING}. 585 \end{methoddesc} 586 587 \begin{methoddesc}[SolverOptions]{getCoarsening}{} 588 Returns the key of the coarsening algorithm to be applied \AMG. 589 \end{methoddesc} 590 591 \begin{methoddesc}[SolverOptions]{setReordering}{\optional{ordering=SolverOptions.DEFAULT_REORDERING}} 592 Sets the key of the reordering method to be applied if supported by the solver. Some direct solvers support reordering to optimize compute time and storage use during elimination. The value of \var{ordering} must be one of the constants 593 \member{SolverOptions.NO_REORDERING}, \member{SolverOptions.MINIMUM_FILL_IN}, 594 \member{SolverOptions.NESTED_DISSECTION}, or \member{SolverOptions.DEFAULT_REORDERING}. 595 \end{methoddesc} 596 597 \begin{methoddesc}[SolverOptions]{getReordering}{} 598 Returns the key of the reordering method to be applied if supported by the solver. 599 \end{methoddesc} 600 601 \begin{methoddesc}[SolverOptions]{setRestart}{\optional{restart=None}} 602 Sets the number of iterations steps after which \GMRES is performing a restart. 603 If \var{restart} is equal to \var{None} no restart is performed. 604 \end{methoddesc} 605 606 607 \begin{methoddesc}[SolverOptions]{getRestart}{} 608 Returns the number of iterations steps after which \GMRES is performing a restart. 609 \end{methoddesc} 610 611 \begin{methoddesc}[SolverOptions]{setTruncation}{\optional{truncation=20}} 612 Sets the number of residuals in \GMRES to be stored for orthogonalization. The more residuals are stored the faster \GMRES converges but 613 \end{methoddesc} 614 615 \begin{methoddesc}[SolverOptions]{getTruncation}{} 616 Returns the number of residuals in \GMRES to be stored for orthogonalization 617 \end{methoddesc} 618 619 620 \begin{methoddesc}[SolverOptions]{setIterMax}{\optional{iter_max=10000}} 621 Sets the maximum number of iteration steps 622 \end{methoddesc} 623 624 \begin{methoddesc}[SolverOptions]{getIterMax}{} 625 Returns maximum number of iteration steps 626 \end{methoddesc} 627 628 \begin{methoddesc}[SolverOptions]{setLevelMax}{\optional{level_max=10}} 629 Sets the maximum number of coarsening levels to be used in the \AMG solver or preconditioner. 630 \end{methoddesc} 631 632 \begin{methoddesc}[SolverOptions]{getLevelMax}{} 633 Returns the maximum number of coarsening levels to be used in an algebraic multi level solver or preconditioner 634 \end{methoddesc} 635 636 \begin{methoddesc}[SolverOptions]{setCoarseningThreshold}{\optional{theta=0.25}} 637 Sets the threshold for coarsening in the \AMG solver or preconditioner 638 \end{methoddesc} 639 640 \begin{methoddesc}[SolverOptions]{getCoarseningThreshold}{} 641 Returns the threshold for coarsening in the \AMG solver or preconditioner 642 \end{methoddesc} 643 644 \begin{methoddesc}[SolverOptions]{setMinCoarseMatrixSize}{\optional{size=500}} 645 Sets the minumum size of the coarsest level matrix in \AMG. 646 \end{methoddesc} 647 648 \begin{methoddesc}[SolverOptions]{getMinCoarseMatrixSize}{} 649 Returns the minumum size of the coarsest level matrix in \AMG. 650 \end{methoddesc} 651 652 \begin{methoddesc}[SolverOptions]{setSmoother}{\optional{smoother=\GAUSSSEIDEL}} 653 Sets the \JACOBI or \GAUSSSEIDEL smoother to be used in \AMG. 654 \end{methoddesc} 655 656 \begin{methoddesc}[SolverOptions]{getSmoother}{} 657 Returns the key for \JACOBI or \GAUSSSEIDEL smoother used in \AMG. 658 \end{methoddesc} 659 660 \begin{methoddesc}[SolverOptions]{setNumSweeps}{\optional{sweeps=2}} 661 Sets the number of sweeps in a \JACOBI or \GAUSSSEIDEL preconditioner. 662 \end{methoddesc} 663 664 \begin{methoddesc}[SolverOptions]{getNumSweeps}{} 665 Returns the number of sweeps in a \JACOBI or \GAUSSSEIDEL preconditioner. 666 \end{methoddesc} 667 668 \begin{methoddesc}[SolverOptions]{setNumPreSweeps}{\optional{sweeps=2}} 669 Sets the number of sweeps in the pre-smoothing step of \AMG 670 \end{methoddesc} 671 672 \begin{methoddesc}[SolverOptions]{getNumPreSweeps}{} 673 Returns the number of sweeps in the pre-smoothing step of \AMG 674 \end{methoddesc} 675 676 \begin{methoddesc}[SolverOptions]{setNumPostSweeps}{\optional{sweeps=2}} 677 Sets the number of sweeps in the post-smoothing step of \AMG 678 \end{methoddesc} 679 680 \begin{methoddesc}[SolverOptions]{getNumPostSweeps}{} 681 Returns he number of sweeps sweeps in the post-smoothing step of \AMG 682 \end{methoddesc} 683 684 \begin{methoddesc}[SolverOptions]{setTolerance}{\optional{rtol=1.e-8}} 685 Sets the relative tolerance for the solver. The actually meaning of tolerance depends 686 on the underlying PDE library. In most cases, the tolerance 687 will only consider the error from solving the discrete problem but will 688 not consider any discretization error. 689 \end{methoddesc} 690 691 \begin{methoddesc}[SolverOptions]{getTolerance}{} 692 Returns the relative tolerance for the solver 693 \end{methoddesc} 694 695 \begin{methoddesc}[SolverOptions]{setAbsoluteTolerance}{\optional{atol=0.}} 696 Sets the absolute tolerance for the solver. The actually meaning of tolerance depends 697 on the underlying PDE library. In most cases, the tolerance 698 will only consider the error from solving the discrete problem but will 699 not consider any discretization error. 700 \end{methoddesc} 701 702 \begin{methoddesc}[SolverOptions]{getAbsoluteTolerance}{} 703 Returns the absolute tolerance for the solver 704 \end{methoddesc} 705 706 707 \begin{methoddesc}[SolverOptions]{setInnerTolerance}{\optional{rtol=0.9}} 708 Sets the relative tolerance for an inner iteration scheme for instance 709 on the coarsest level in a multi-level scheme. 710 \end{methoddesc} 711 712 \begin{methoddesc}[SolverOptions]{getInnerTolerance}{} 713 Returns the relative tolerance for an inner iteration scheme 714 \end{methoddesc} 715 716 \begin{methoddesc}[SolverOptions]{setDropTolerance}{\optional{drop_tol=0.01}} 717 Sets the relative drop tolerance in ILUT 718 \end{methoddesc} 719 720 \begin{methoddesc}[SolverOptions]{getDropTolerance}{} 721 Returns the relative drop tolerance in \ILUT 722 \end{methoddesc} 723 724 725 \begin{methoddesc}[SolverOptions]{setDropStorage}{\optional{storage=2.}} 726 Sets the maximum allowed increase in storage for \ILUT. \var{storage}=2 would mean that a doubling of the storage needed for the coefficient matrix is allowed in the \ILUT factorization. 727 \end{methoddesc} 728 729 \begin{methoddesc}[SolverOptions]{getDropStorage}{} 730 Returns the maximum allowed increase in storage for \ILUT 731 \end{methoddesc} 732 733 \begin{methoddesc}[SolverOptions]{setRelaxationFactor}{\optional{factor=0.3}} 734 Sets the relaxation factor used to add dropped elements in \RILU to the main diagonal. 735 \end{methoddesc} 736 737 \begin{methoddesc}[SolverOptions]{getRelaxationFactor}{} 738 Returns the relaxation factor used to add dropped elements in RILU to the main diagonal. 739 \end{methoddesc} 740 741 \begin{methoddesc}[SolverOptions]{isSymmetric}{} 742 Returns \True is the descrete system is indicated as symmetric. 743 \end{methoddesc} 744 745 \begin{methoddesc}[SolverOptions]{setSymmetryOn}{} 746 Sets the symmetry flag to indicate that the coefficient matrix is symmetric. 747 \end{methoddesc} 748 749 \begin{methoddesc}[SolverOptions]{setSymmetryOff}{} 750 Clears the symmetry flag for the coefficient matrix. 751 \end{methoddesc} 752 753 \begin{methoddesc}[SolverOptions]{isVerbose}{} 754 Returns \True if the solver is expected to be verbose. 755 \end{methoddesc} 756 757 758 \begin{methoddesc}[SolverOptions]{setVerbosityOn}{} 759 Switches the verbosity of the solver on. 760 \end{methoddesc} 761 762 763 \begin{methoddesc}[SolverOptions]{setVerbosityOff}{} 764 Switches the verbosity of the solver off. 765 \end{methoddesc} 766 767 768 \begin{methoddesc}[SolverOptions]{adaptInnerTolerance}{} 769 Returns \True if the tolerance of the inner solver is selected automatically. 770 Otherwise the inner tolerance set by \member{setInnerTolerance} is used. 771 \end{methoddesc} 772 773 \begin{methoddesc}[SolverOptions]{setInnerToleranceAdaptionOn}{} 774 Switches the automatic selection of inner tolerance on 775 \end{methoddesc} 776 777 \begin{methoddesc}[SolverOptions]{setInnerToleranceAdaptionOff}{} 778 Switches the automatic selection of inner tolerance off. 779 \end{methoddesc} 780 781 \begin{methoddesc}[SolverOptions]{setInnerIterMax}{\optional{iter_max=10}} 782 Sets the maximum number of iteration steps for the inner iteration. 783 \end{methoddesc} 784 785 \begin{methoddesc}[SolverOptions]{getInnerIterMax}{} 786 Returns maximum number of inner iteration steps. 787 \end{methoddesc} 788 789 \begin{methoddesc}[SolverOptions]{acceptConvergenceFailure}{} 790 Returns \True if a failure to meet the stopping criteria within the 791 given number of iteration steps is not raising in exception. This is useful 792 if a solver is used in a non-linear context where the non-linear solver can 793 continue even if the returned the solution does not necessarily meet the 794 stopping criteria. One can use the \member{hasConverged} method to check if the 795 last call to the solver was successful. 796 \end{methoddesc} 797 798 \begin{methoddesc}[SolverOptions]{setAcceptanceConvergenceFailureOn}{} 799 Switches the acceptance of a failure of convergence on. 800 \end{methoddesc} 801 802 \begin{methoddesc}[SolverOptions]{setAcceptanceConvergenceFailureOff}{} 803 Switches the acceptance of a failure of convergence off. 804 \end{methoddesc} 805 806 \begin{memberdesc}[SolverOptions]{DEFAULT} 807 default method, preconditioner or package to be used to solve the PDE. An appropriate method should be 808 chosen by the used PDE solver library. 809 \end{memberdesc} 810 811 \begin{memberdesc}[SolverOptions]{MKL} 812 the \MKL library by Intel,~\Ref{MKL}\footnote{The \MKL library will only be available when the Intel compilation environment is used.}. 813 \end{memberdesc} 814 815 \begin{memberdesc}[SolverOptions]{UMFPACK} 816 the \UMFPACK,~\Ref{UMFPACK}. Remark: \UMFPACK is not parallelized. 817 \end{memberdesc} 818 819 \begin{memberdesc}[SolverOptions]{PASO} 820 \PASO is the solver library of \finley, see \Sec{CHAPTER ON FINLEY}. 821 \end{memberdesc} 822 823 \begin{memberdesc}[SolverOptions]{ITERATIVE} 824 the default iterative method and preconditioner. The actually used method depends on the PDE solver library and the solver package been chosen. Typically, \PCG is used for symmetric PDEsand \BiCGStab otherwise, both with \JACOBI preconditioner. 825 \end{memberdesc} 826 827 \begin{memberdesc}[SolverOptions]{DIRECT} 828 the default direct linear solver. 829 \end{memberdesc} 830 831 \begin{memberdesc}[SolverOptions]{CHOLEVSKY} 832 direct solver based on Cholevsky factorization (or similar), see~\Ref{Saad}. The solver will require a symmetric PDE. 833 \end{memberdesc} 834 835 \begin{memberdesc}[SolverOptions]{PCG} 836 preconditioned conjugate gradient method, see~\Ref{WEISS}\index{linear solver!PCG}\index{PCG}. The solver will require a symmetric PDE. 837 \end{memberdesc} 838 839 \begin{memberdesc}[SolverOptions]{TFQMR} 840 transpose-free quasi-minimal residual method, see~\Ref{WEISS}\index{linear solver!TFQMR}\index{TFQMR}. \end{memberdesc} 841 842 \begin{memberdesc}[SolverOptions]{GMRES} 843 the GMRES method, see~\Ref{WEISS}\index{linear solver!GMRES}\index{GMRES}. Truncation and restart are controlled by the parameters 844 \var{truncation} and \var{restart} of \method{getSolution}. 845 \end{memberdesc} 846 847 \begin{memberdesc}[SolverOptions]{MINRES} 848 minimal residual method method, \index{linear solver!MINRES}\index{MINRES} \end{memberdesc} 849 850 \begin{memberdesc}[SolverOptions]{LUMPING} 851 uses lumping to solve the system of linear equations~\index{linear solver!lumping}\index{lumping}. This solver technique 852 condenses the stiffness matrix to a diagonal matrix so the solution of the linear systems becomes very cheap. It can be used when 853 only \var{D} is present but in any case has to applied with care. The difference in the solutions with and without lumping can be significant 854 but is expected to converge to zero when the mesh gets finer. 855 Lumping does not use the linear system solver library. 856 \end{memberdesc} 857 858 \begin{memberdesc}[SolverOptions]{PRES20} 859 the GMRES method with truncation after five residuals and 860 restart after 20 steps, see~\Ref{WEISS}. 861 \end{memberdesc} 862 863 \begin{memberdesc}[SolverOptions]{CGS} 864 conjugate gradient squared method, see~\Ref{WEISS}. 865 \end{memberdesc} 866 867 \begin{memberdesc}[SolverOptions]{BICGSTAB} 868 stabilized bi-conjugate gradients methods, see~\Ref{WEISS}. 869 \end{memberdesc} 870 871 \begin{memberdesc}[SolverOptions]{SSOR} 872 symmetric successive over-relaxation method, see~\Ref{WEISS}. Typically used as preconditioner but some linear solver libraries support 873 this as a solver. 874 \end{memberdesc} 875 876 \begin{memberdesc}[SolverOptions]{ILU0} 877 the incomplete LU factorization preconditioner with no fill-in, see~\Ref{Saad}. 878 \end{memberdesc} 879 880 \begin{memberdesc}[SolverOptions]{ILUT} 881 the incomplete LU factorization preconditioner with fill-in, see~\Ref{Saad}. During the LU-factorization element with 882 relative size less then \member{getDropTolerance} are dropped. Moreover, the size of the LU-factorization is restricted to the 883 \member{getDropStorage}-fold of the stiffness matrix. \member{getDropTolerance} and \member{getDropStorage} are both set in the 884 \method{getSolution} call. 885 \end{memberdesc} 886 887 \begin{memberdesc}[SolverOptions]{JACOBI} 888 the Jacobi preconditioner, see~\Ref{Saad}. 889 \end{memberdesc} 890 891 892 \begin{memberdesc}[SolverOptions]{AMG} 893 the algebraic--multi grid method, see~\Ref{AMG}. This method can be used as linear solver method but is more robust when used 894 in a preconditioner. 895 \end{memberdesc} 896 897 \begin{memberdesc}[SolverOptions]{GAUSS_SEIDEL} 898 the symmetric Gauss-Seidel preconditioner, see~\Ref{Saad}. 899 \member{getNumSweeps()} is the number of sweeps used. 900 \end{memberdesc} 901 902 \begin{memberdesc}[SolverOptions]{RILU} 903 relaxed incomplete LU factorization preconditioner, see~\Ref{RELAXILU}. This method is similar to the one used for \ILU but dropped elements are added to the main diagonal 904 with the relaxation factor \member{getRelaxationFactor}. 905 \end{memberdesc} 906 907 \begin{memberdesc}[SolverOptions]{REC_ILU} 908 recursive incomplete LU factorization preconditioner, see~\Ref{RILU}. This method is similar to the one used for \ILU but applies reordering during the factorization. 909 \end{memberdesc} 910 911 \begin{memberdesc}[SolverOptions]{NO_REORDERING} 912 no ordering is used during factorization. 913 \end{memberdesc} 914 915 \begin{memberdesc}[SolverOptions]{DEFAULT_REORDERING} 916 the default reordering method during factorization. 917 \end{memberdesc} 918 919 \begin{memberdesc}[SolverOptions]{MINIMUM_FILL_IN} 920 applies reordering before factorization using a fill-in minimization strategy. You have to check with the particular solver library or 921 linear solver package if this is supported. In any case, it is advisable to apply reordering on the mesh to minimize fill-in. 922 \end{memberdesc} 923 924 \begin{memberdesc}[SolverOptions]{NESTED_DISSECTION} 925 applies reordering before factorization using a nested dissection strategy. You have to check with the particular solver library or 926 linear solver package if this is supported. In any case, it is advisable to apply reordering on the mesh to minimize fill-in. 927 \end{memberdesc} 928 929 \begin{memberdesc}[SolverOptions]{TRILINOS} 930 the Trilinos library is used as a solver~\Ref{TRILINOS} 931 \end{memberdesc} 932 933 \begin{memberdesc}[SolverOptions]{SUPER_LU} 934 the SuperLU library is used as a solver~\Ref{SuperLU} 935 \end{memberdesc} 936 937 \begin{memberdesc}[SolverOptions]{PASTIX} 938 the Pastix library is used as a solver~\Ref{PASTIX} 939 \end{memberdesc} 940 941 942 \begin{memberdesc}[SolverOptions]{STANDARD_COARSENING} 943 \AMG coarsening method by Ruge and Stueben using measure of importance principle~\cite{Multigrid}. 944 \end{memberdesc} 945 946 \begin{memberdesc}[SolverOptions]{YAIR_SHAPIRA_COARSENING} 947 \AMG coarsening method by Yair-Shapira 948 \end{memberdesc} 949 950 \begin{memberdesc}[SolverOptions]{RUGE_STUEBEN_COARSENING} \AMG coarsening method by Ruge and Stueben using greedy algorithm for splitting. 951 \end{memberdesc} 952 953 \begin{memberdesc}[SolverOptions]{AGGREGATION_COARSENING} \AMG coarsening using (symmetric) aggregation using greedy algorithm for splitting. 954 \end{memberdesc} 955 956 \begin{memberdesc}[SolverOptions]{NO_PRECONDITIONER} 957 no preconditioner is applied. 958 \end{memberdesc} 959

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