Actual source code: test1.c

slepc-3.18.3 2023-03-24
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  1: /*
  2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
  4:    Copyright (c) 2002-, Universitat Politecnica de Valencia, Spain

  6:    This file is part of SLEPc.
  7:    SLEPc is distributed under a 2-clause BSD license (see LICENSE).
  8:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  9: */

 11: static char help[] = "Test the solution of a SVD without calling SVDSetFromOptions (based on ex8.c).\n\n"
 12:   "The command line options are:\n"
 13:   "  -n <n>, where <n> = matrix dimension.\n"
 14:   "  -type <svd_type> = svd type to test.\n\n";

 16: #include <slepcsvd.h>

 18: /*
 19:    This example computes the singular values of an nxn Grcar matrix,
 20:    which is a nonsymmetric Toeplitz matrix:

 22:               |  1  1  1  1               |
 23:               | -1  1  1  1  1            |
 24:               |    -1  1  1  1  1         |
 25:               |       .  .  .  .  .       |
 26:           A = |          .  .  .  .  .    |
 27:               |            -1  1  1  1  1 |
 28:               |               -1  1  1  1 |
 29:               |                  -1  1  1 |
 30:               |                     -1  1 |

 32:  */

 34: int main(int argc,char **argv)
 35: {
 36:   Mat            A;               /* Grcar matrix */
 37:   SVD            svd;             /* singular value solver context */
 38:   PetscInt       N=30,Istart,Iend,i,col[5],nconv1,nconv2;
 39:   PetscScalar    value[] = { -1, 1, 1, 1, 1 };
 40:   PetscReal      sigma_1,sigma_n;
 41:   char           svdtype[30] = "cross",epstype[30] = "";
 42:   PetscBool      flg;
 43:   EPS            eps;

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

 48:   PetscOptionsGetInt(NULL,NULL,"-n",&N,NULL);
 49:   PetscOptionsGetString(NULL,NULL,"-type",svdtype,sizeof(svdtype),NULL);
 50:   PetscOptionsGetString(NULL,NULL,"-epstype",epstype,sizeof(epstype),&flg);
 51:   PetscPrintf(PETSC_COMM_WORLD,"\nEstimate the condition number of a Grcar matrix, n=%" PetscInt_FMT,N);
 52:   PetscPrintf(PETSC_COMM_WORLD,"\n\n");

 54:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 55:         Generate the matrix
 56:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

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

 63:   MatGetOwnershipRange(A,&Istart,&Iend);
 64:   for (i=Istart;i<Iend;i++) {
 65:     col[0]=i-1; col[1]=i; col[2]=i+1; col[3]=i+2; col[4]=i+3;
 66:     if (i==0) MatSetValues(A,1,&i,4,col+1,value+1,INSERT_VALUES);
 67:     else MatSetValues(A,1,&i,PetscMin(5,N-i+1),col,value,INSERT_VALUES);
 68:   }

 70:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
 71:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);

 73:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 74:          Create the singular value solver and set the solution method
 75:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 77:   /*
 78:      Create singular value context
 79:   */
 80:   SVDCreate(PETSC_COMM_WORLD,&svd);

 82:   /*
 83:      Set operator
 84:   */
 85:   SVDSetOperators(svd,A,NULL);

 87:   /*
 88:      Set solver parameters at runtime
 89:   */
 90:   SVDSetType(svd,svdtype);
 91:   if (flg) {
 92:     PetscObjectTypeCompare((PetscObject)svd,SVDCROSS,&flg);
 93:     if (flg) {
 94:       SVDCrossGetEPS(svd,&eps);
 95:       EPSSetType(eps,epstype);
 96:     }
 97:     PetscObjectTypeCompare((PetscObject)svd,SVDCYCLIC,&flg);
 98:     if (flg) {
 99:       SVDCyclicGetEPS(svd,&eps);
100:       EPSSetType(eps,epstype);
101:     }
102:   }
103:   SVDSetDimensions(svd,1,PETSC_DEFAULT,PETSC_DEFAULT);
104:   SVDSetTolerances(svd,1e-6,1000);

106:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
107:                       Compute the singular values
108:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

110:   /*
111:      First request the largest singular value
112:   */
113:   SVDSetWhichSingularTriplets(svd,SVD_LARGEST);
114:   SVDSolve(svd);
115:   /*
116:      Get number of converged singular values
117:   */
118:   SVDGetConverged(svd,&nconv1);
119:   /*
120:      Get converged singular values: largest singular value is stored in sigma_1.
121:      In this example, we are not interested in the singular vectors
122:   */
123:   if (nconv1 > 0) SVDGetSingularTriplet(svd,0,&sigma_1,NULL,NULL);
124:   else PetscPrintf(PETSC_COMM_WORLD," Unable to compute large singular value!\n\n");

126:   /*
127:      Request the smallest singular value
128:   */
129:   SVDSetWhichSingularTriplets(svd,SVD_SMALLEST);
130:   SVDSolve(svd);
131:   /*
132:      Get number of converged triplets
133:   */
134:   SVDGetConverged(svd,&nconv2);
135:   /*
136:      Get converged singular values: smallest singular value is stored in sigma_n.
137:      As before, we are not interested in the singular vectors
138:   */
139:   if (nconv2 > 0) SVDGetSingularTriplet(svd,0,&sigma_n,NULL,NULL);
140:   else PetscPrintf(PETSC_COMM_WORLD," Unable to compute small singular value!\n\n");

142:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
143:                     Display solution and clean up
144:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
145:   if (nconv1 > 0 && nconv2 > 0) {
146:     PetscPrintf(PETSC_COMM_WORLD," Computed singular values: sigma_1=%.4f, sigma_n=%.4f\n",(double)sigma_1,(double)sigma_n);
147:     PetscPrintf(PETSC_COMM_WORLD," Estimated condition number: sigma_1/sigma_n=%.4f\n\n",(double)(sigma_1/sigma_n));
148:   }

150:   /*
151:      Free work space
152:   */
153:   SVDDestroy(&svd);
154:   MatDestroy(&A);
155:   SlepcFinalize();
156:   return 0;
157: }

159: /*TEST

161:    test:
162:       suffix: 1
163:       args: -type {{lanczos trlanczos cross cyclic lapack}}

165:    test:
166:       suffix: 1_cross_gd
167:       args: -type cross -epstype gd
168:       output_file: output/test1_1.out

170:    test:
171:       suffix: 1_cyclic_gd
172:       args: -type cyclic -epstype gd
173:       output_file: output/test1_1.out
174:       requires: !single

176:    test:
177:       suffix: 1_primme
178:       args: -type primme
179:       requires: primme
180:       output_file: output/test1_1.out

182: TEST*/