Actual source code: ex10.c

slepc-3.5.2 2014-10-10
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  1: /*
  2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
  4:    Copyright (c) 2002-2014, Universitat Politecnica de Valencia, Spain

  6:    This file is part of SLEPc.

  8:    SLEPc is free software: you can redistribute it and/or modify it under  the
  9:    terms of version 3 of the GNU Lesser General Public License as published by
 10:    the Free Software Foundation.

 12:    SLEPc  is  distributed in the hope that it will be useful, but WITHOUT  ANY
 13:    WARRANTY;  without even the implied warranty of MERCHANTABILITY or  FITNESS
 14:    FOR  A  PARTICULAR PURPOSE. See the GNU Lesser General Public  License  for
 15:    more details.

 17:    You  should have received a copy of the GNU Lesser General  Public  License
 18:    along with SLEPc. If not, see <http://www.gnu.org/licenses/>.
 19:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 20: */

 22: static char help[] = "Illustrates the use of shell spectral transformations. "
 23:   "The problem to be solved is the same as ex1.c and"
 24:   "corresponds to the Laplacian operator in 1 dimension.\n\n"
 25:   "The command line options are:\n"
 26:   "  -n <n>, where <n> = number of grid subdivisions = matrix dimension.\n\n";

 28: #include <slepceps.h>

 30: /* Define context for user-provided spectral transformation */
 31: typedef struct {
 32:   KSP        ksp;
 33: } SampleShellST;

 35: /* Declare routines for user-provided spectral transformation */
 36: PetscErrorCode STCreate_User(SampleShellST**);
 37: PetscErrorCode STSetUp_User(SampleShellST*,ST);
 38: PetscErrorCode STApply_User(ST,Vec,Vec);
 39: PetscErrorCode STBackTransform_User(ST,PetscInt,PetscScalar*,PetscScalar*);
 40: PetscErrorCode STDestroy_User(SampleShellST*);

 44: int main (int argc,char **argv)
 45: {
 46:   Mat            A;               /* operator matrix */
 47:   EPS            eps;             /* eigenproblem solver context */
 48:   ST             st;              /* spectral transformation context */
 49:   SampleShellST  *shell;          /* user-defined spectral transform context */
 50:   EPSType        type;
 51:   PetscScalar    value[3];
 52:   PetscInt       n=30,i,col[3],Istart,Iend,FirstBlock=0,LastBlock=0,nev;
 53:   PetscBool      isShell;

 56:   SlepcInitialize(&argc,&argv,(char*)0,help);

 58:   PetscOptionsGetInt(NULL,"-n",&n,NULL);
 59:   PetscPrintf(PETSC_COMM_WORLD,"\n1-D Laplacian Eigenproblem (shell-enabled), n=%D\n\n",n);

 61:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 62:      Compute the operator matrix that defines the eigensystem, Ax=kx
 63:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 65:   MatCreate(PETSC_COMM_WORLD,&A);
 66:   MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n);
 67:   MatSetFromOptions(A);
 68:   MatSetUp(A);

 70:   MatGetOwnershipRange(A,&Istart,&Iend);
 71:   if (Istart==0) FirstBlock=PETSC_TRUE;
 72:   if (Iend==n) LastBlock=PETSC_TRUE;
 73:   value[0]=-1.0; value[1]=2.0; value[2]=-1.0;
 74:   for (i=(FirstBlock? Istart+1: Istart); i<(LastBlock? Iend-1: Iend); i++) {
 75:     col[0]=i-1; col[1]=i; col[2]=i+1;
 76:     MatSetValues(A,1,&i,3,col,value,INSERT_VALUES);
 77:   }
 78:   if (LastBlock) {
 79:     i=n-1; col[0]=n-2; col[1]=n-1;
 80:     MatSetValues(A,1,&i,2,col,value,INSERT_VALUES);
 81:   }
 82:   if (FirstBlock) {
 83:     i=0; col[0]=0; col[1]=1; value[0]=2.0; value[1]=-1.0;
 84:     MatSetValues(A,1,&i,2,col,value,INSERT_VALUES);
 85:   }

 87:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
 88:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);

 90:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 91:                 Create the eigensolver and set various options
 92:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 94:   /*
 95:      Create eigensolver context
 96:   */
 97:   EPSCreate(PETSC_COMM_WORLD,&eps);

 99:   /*
100:      Set operators. In this case, it is a standard eigenvalue problem
101:   */
102:   EPSSetOperators(eps,A,NULL);
103:   EPSSetProblemType(eps,EPS_HEP);

105:   /*
106:      Set solver parameters at runtime
107:   */
108:   EPSSetFromOptions(eps);

110:   /*
111:      Initialize shell spectral transformation if selected by user
112:   */
113:   EPSGetST(eps,&st);
114:   PetscObjectTypeCompare((PetscObject)st,STSHELL,&isShell);
115:   if (isShell) {
116:     /* Change sorting criterion since this ST example computes values
117:        closest to 0 */
118:     EPSSetWhichEigenpairs(eps,EPS_SMALLEST_REAL);

120:     /* (Optional) Create a context for the user-defined spectral tranform;
121:        this context can be defined to contain any application-specific data. */
122:     STCreate_User(&shell);

124:     /* (Required) Set the user-defined routine for applying the operator */
125:     STShellSetApply(st,STApply_User);
126:     STShellSetContext(st,shell);

128:     /* (Optional) Set the user-defined routine for back-transformation */
129:     STShellSetBackTransform(st,STBackTransform_User);

131:     /* (Optional) Set a name for the transformation, used for STView() */
132:     PetscObjectSetName((PetscObject)st,"MyTransformation");

134:     /* (Optional) Do any setup required for the new transformation */
135:     STSetUp_User(shell,st);
136:   }

138:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
139:                       Solve the eigensystem
140:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

142:   EPSSolve(eps);

144:   /*
145:      Optional: Get some information from the solver and display it
146:   */
147:   EPSGetType(eps,&type);
148:   PetscPrintf(PETSC_COMM_WORLD," Solution method: %s\n\n",type);
149:   EPSGetDimensions(eps,&nev,NULL,NULL);
150:   PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %D\n",nev);

152:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
153:                     Display solution and clean up
154:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

156:   EPSPrintSolution(eps,NULL);
157:   if (isShell) {
158:     STDestroy_User(shell);
159:   }
160:   EPSDestroy(&eps);
161:   MatDestroy(&A);
162:   SlepcFinalize();
163:   return 0;
164: }

166: /***********************************************************************/
167: /*     Routines for a user-defined shell spectral transformation       */
168: /***********************************************************************/

172: /*
173:    STCreate_User - This routine creates a user-defined
174:    spectral transformation context.

176:    Output Parameter:
177: .  shell - user-defined spectral transformation context
178: */
179: PetscErrorCode STCreate_User(SampleShellST **shell)
180: {
181:   SampleShellST  *newctx;

185:   PetscNew(&newctx);
186:   KSPCreate(PETSC_COMM_WORLD,&newctx->ksp);
187:   KSPAppendOptionsPrefix(newctx->ksp,"st_");
188:   *shell = newctx;
189:   return(0);
190: }
191: /* ------------------------------------------------------------------- */
194: /*
195:    STSetUp_User - This routine sets up a user-defined
196:    spectral transformation context.

198:    Input Parameters:
199: .  shell - user-defined spectral transformation context
200: .  st    - spectral transformation context containing the operator matrices

202:    Output Parameter:
203: .  shell - fully set up user-defined transformation context

205:    Notes:
206:    In this example, the user-defined transformation is simply OP=A^-1.
207:    Therefore, the eigenpairs converge in reversed order. The KSP object
208:    used for the solution of linear systems with A is handled via the
209:    user-defined context SampleShellST.
210: */
211: PetscErrorCode STSetUp_User(SampleShellST *shell,ST st)
212: {
213:   Mat            A;

217:   STGetOperators(st,0,&A);
218:   KSPSetOperators(shell->ksp,A,A);
219:   KSPSetFromOptions(shell->ksp);
220:   return(0);
221: }
222: /* ------------------------------------------------------------------- */
225: /*
226:    STApply_User - This routine demonstrates the use of a
227:    user-provided spectral transformation.

229:    Input Parameters:
230: .  ctx - optional user-defined context, as set by STShellSetContext()
231: .  x - input vector

233:    Output Parameter:
234: .  y - output vector

236:    Notes:
237:    The transformation implemented in this code is just OP=A^-1 and
238:    therefore it is of little use, merely as an example of working with
239:    a STSHELL.
240: */
241: PetscErrorCode STApply_User(ST st,Vec x,Vec y)
242: {
243:   SampleShellST  *shell;

247:   STShellGetContext(st,(void**)&shell);
248:   KSPSolve(shell->ksp,x,y);
249:   return(0);
250: }
251: /* ------------------------------------------------------------------- */
254: /*
255:    STBackTransform_User - This routine demonstrates the use of a
256:    user-provided spectral transformation.

258:    Input Parameters:
259: +  ctx  - optional user-defined context, as set by STShellSetContext()
260: .  eigr - pointer to real part of eigenvalues
261: -  eigi - pointer to imaginary part of eigenvalues

263:    Output Parameters:
264: +  eigr - modified real part of eigenvalues
265: -  eigi - modified imaginary part of eigenvalues

267:    Notes:
268:    This code implements the back transformation of eigenvalues in
269:    order to retrieve the eigenvalues of the original problem. In this
270:    example, simply set k_i = 1/k_i.
271: */
272: PetscErrorCode STBackTransform_User(ST st,PetscInt n,PetscScalar *eigr,PetscScalar *eigi)
273: {
274:   PetscInt j;

277:   for (j=0;j<n;j++) {
278:     eigr[j] = 1.0 / eigr[j];
279:   }
280:   return(0);
281: }
282: /* ------------------------------------------------------------------- */
285: /*
286:    STDestroy_User - This routine destroys a user-defined
287:    spectral transformation context.

289:    Input Parameter:
290: .  shell - user-defined spectral transformation context
291: */
292: PetscErrorCode STDestroy_User(SampleShellST *shell)
293: {

297:   KSPDestroy(&shell->ksp);
298:   PetscFree(shell);
299:   return(0);
300: }