Actual source code: ex25.c

slepc-3.7.0 2016-05-16
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  1: /*
  2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
  4:    Copyright (c) 2002-2016, 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[] = "Spectrum slicing on generalized symmetric eigenproblem.\n\n"
 23:   "The problem is similar to ex13.c.\n\n"
 24:   "The command line options are:\n"
 25:   "  -n <n>, where <n> = number of grid subdivisions in x dimension.\n"
 26:   "  -m <m>, where <m> = number of grid subdivisions in y dimension.\n";

 28: #include <slepceps.h>

 32: int main(int argc,char **argv)
 33: {
 34:   Mat            A,B;         /* matrices */
 35:   EPS            eps;         /* eigenproblem solver context */
 36:   ST             st;          /* spectral transformation context */
 37:   KSP            ksp;
 38:   PC             pc;
 39:   EPSType        type;
 40:   PetscInt       N,n=10,m,Istart,Iend,II,nev,i,j,*inertias,ns;
 41:   PetscReal      inta,intb,*shifts;
 42:   PetscBool      flag,show=PETSC_FALSE,terse;

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

 47:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
 48:   PetscOptionsGetInt(NULL,NULL,"-m",&m,&flag);
 49:   PetscOptionsGetBool(NULL,NULL,"-show_inertias",&show,NULL);
 50:   if (!flag) m=n;
 51:   N = n*m;
 52:   PetscPrintf(PETSC_COMM_WORLD,"\nSpectrum slicing on GHEP, N=%D (%Dx%D grid)\n\n",N,n,m);

 54:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 55:      Compute the matrices that define the eigensystem, Ax=kBx
 56:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 58:   MatCreate(PETSC_COMM_WORLD,&A);
 59:   MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,N);
 60:   MatSetFromOptions(A);
 61:   MatSetUp(A);

 63:   MatCreate(PETSC_COMM_WORLD,&B);
 64:   MatSetSizes(B,PETSC_DECIDE,PETSC_DECIDE,N,N);
 65:   MatSetFromOptions(B);
 66:   MatSetUp(B);

 68:   MatGetOwnershipRange(A,&Istart,&Iend);
 69:   for (II=Istart;II<Iend;II++) {
 70:     i = II/n; j = II-i*n;
 71:     if (i>0) { MatSetValue(A,II,II-n,-1.0,INSERT_VALUES); }
 72:     if (i<m-1) { MatSetValue(A,II,II+n,-1.0,INSERT_VALUES); }
 73:     if (j>0) { MatSetValue(A,II,II-1,-1.0,INSERT_VALUES); }
 74:     if (j<n-1) { MatSetValue(A,II,II+1,-1.0,INSERT_VALUES); }
 75:     MatSetValue(A,II,II,4.0,INSERT_VALUES);
 76:     MatSetValue(B,II,II,4.0,INSERT_VALUES);
 77:   }

 79:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
 80:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
 81:   MatAssemblyBegin(B,MAT_FINAL_ASSEMBLY);
 82:   MatAssemblyEnd(B,MAT_FINAL_ASSEMBLY);

 84:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 85:                 Create the eigensolver and set various options
 86:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 88:   /*
 89:      Create eigensolver context
 90:   */
 91:   EPSCreate(PETSC_COMM_WORLD,&eps);

 93:   /*
 94:      Set operators and set problem type
 95:   */
 96:   EPSSetOperators(eps,A,B);
 97:   EPSSetProblemType(eps,EPS_GHEP);

 99:   /*
100:      Set interval for spectrum slicing
101:   */
102:   inta = 0.1;
103:   intb = 0.2;
104:   EPSSetInterval(eps,inta,intb);
105:   EPSSetWhichEigenpairs(eps,EPS_ALL);

107:   /*
108:      Spectrum slicing requires Krylov-Schur
109:   */
110:   EPSSetType(eps,EPSKRYLOVSCHUR);

112:   /*
113:      Set shift-and-invert with Cholesky; select MUMPS if available
114:   */

116:   EPSGetST(eps,&st);
117:   STSetType(st,STSINVERT);
118:   
119:   STGetKSP(st,&ksp);
120:   KSPSetType(ksp,KSPPREONLY);
121:   KSPGetPC(ksp,&pc);
122:   PCSetType(pc,PCCHOLESKY);
123:     
124: #if defined(PETSC_HAVE_MUMPS)
125: #if defined(PETSC_USE_COMPLEX)
126:   SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP,"Spectrum slicing with MUMPS is not available for complex scalars");
127: #endif
128:   EPSKrylovSchurSetDetectZeros(eps,PETSC_TRUE);  /* enforce zero detection */
129:   PCFactorSetMatSolverPackage(pc,MATSOLVERMUMPS);
130:   /*
131:      Add several MUMPS options (currently there is no better way of setting this in program):
132:      '-mat_mumps_icntl_13 1': turn off ScaLAPACK for matrix inertia 
133:      '-mat_mumps_icntl_24 1': detect null pivots in factorization (for the case that a shift is equal to an eigenvalue)
134:      '-mat_mumps_cntl_3 <tol>': a tolerance used for null pivot detection (must be larger than machine epsilon)

136:      Note: depending on the interval, it may be necessary also to increase the workspace:
137:      '-mat_mumps_icntl_14 <percentage>': increase workspace with a percentage (50, 100 or more)
138:   */
139:   PetscOptionsInsertString(NULL,"-mat_mumps_icntl_13 1 -mat_mumps_icntl_24 1 -mat_mumps_cntl_3 1e-12"); 
140: #endif

142:   /*
143:      Set solver parameters at runtime
144:   */
145:   EPSSetFromOptions(eps);

147:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
148:                       Solve the eigensystem
149:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
150:   EPSSetUp(eps);
151:   if (show) {
152:     EPSKrylovSchurGetInertias(eps,&ns,&shifts,&inertias);  
153:     PetscPrintf(PETSC_COMM_WORLD,"Subintervals (after setup):\n");
154:     for (i=0;i<ns;i++) { PetscPrintf(PETSC_COMM_WORLD,"Shift %g  Inertia %D \n",shifts[i],inertias[i]); }
155:     PetscPrintf(PETSC_COMM_WORLD,"\n");
156:     PetscFree(shifts);
157:     PetscFree(inertias);
158:   }
159:   EPSSolve(eps);
160:   if (show) {
161:     EPSKrylovSchurGetInertias(eps,&ns,&shifts,&inertias);  
162:     PetscPrintf(PETSC_COMM_WORLD,"All shifts (after solve):\n");
163:     for (i=0;i<ns;i++) { PetscPrintf(PETSC_COMM_WORLD,"Shift %g  Inertia %D \n",shifts[i],inertias[i]); }
164:     PetscPrintf(PETSC_COMM_WORLD,"\n");
165:     PetscFree(shifts);
166:     PetscFree(inertias);
167:   }

169:   /*
170:      Show eigenvalues in interval and print solution
171:   */
172:   EPSGetType(eps,&type);
173:   PetscPrintf(PETSC_COMM_WORLD," Solution method: %s\n\n",type);
174:   EPSGetDimensions(eps,&nev,NULL,NULL);
175:   EPSGetInterval(eps,&inta,&intb);
176:   PetscPrintf(PETSC_COMM_WORLD," %D eigenvalues found in [%g, %g]\n",nev,(double)inta,(double)intb);

178:   /*
179:      Show detailed info unless -terse option is given by user
180:    */
181:   PetscOptionsHasName(NULL,NULL,"-terse",&terse);
182:   if (terse) {
183:     EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL);
184:   } else {
185:     PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL);
186:     EPSReasonView(eps,PETSC_VIEWER_STDOUT_WORLD);
187:     EPSErrorView(eps,EPS_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD);
188:     PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
189:   }

191:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
192:                     Clean up
193:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
194:   EPSDestroy(&eps);
195:   MatDestroy(&A);
196:   MatDestroy(&B);
197:   SlepcFinalize();
198:   return ierr;
199: }