Actual source code: test9.c
slepc-3.18.0 2022-10-01
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[] = "Tests multiple calls to SVDSolve with different matrix size.\n\n"
12: "The command line options are:\n"
13: " -n <n>, where <n> = matrix dimension.\n\n";
15: #include <slepcsvd.h>
17: /*
18: This example computes the singular values of an nxn Grcar matrix,
19: which is a nonsymmetric Toeplitz matrix:
21: | 1 1 1 1 |
22: | -1 1 1 1 1 |
23: | -1 1 1 1 1 |
24: | . . . . . |
25: A = | . . . . . |
26: | -1 1 1 1 1 |
27: | -1 1 1 1 |
28: | -1 1 1 |
29: | -1 1 |
31: */
33: int main(int argc,char **argv)
34: {
35: Mat A,B;
36: SVD svd;
37: PetscInt N=30,Istart,Iend,i,col[5];
38: PetscScalar value[] = { -1, 1, 1, 1, 1 };
41: SlepcInitialize(&argc,&argv,(char*)0,help);
42: PetscOptionsGetInt(NULL,NULL,"-n",&N,NULL);
43: PetscPrintf(PETSC_COMM_WORLD,"\nSingular values of a Grcar matrix, n=%" PetscInt_FMT "\n\n",N);
45: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
46: Generate the matrix of size N
47: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
49: MatCreate(PETSC_COMM_WORLD,&A);
50: MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,N);
51: MatSetFromOptions(A);
52: MatSetUp(A);
53: MatGetOwnershipRange(A,&Istart,&Iend);
54: for (i=Istart;i<Iend;i++) {
55: col[0]=i-1; col[1]=i; col[2]=i+1; col[3]=i+2; col[4]=i+3;
56: if (i==0) MatSetValues(A,1,&i,4,col+1,value+1,INSERT_VALUES);
57: else MatSetValues(A,1,&i,PetscMin(5,N-i+1),col,value,INSERT_VALUES);
58: }
59: MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
60: MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
62: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
63: Create the singular value solver, set options and solve
64: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
66: SVDCreate(PETSC_COMM_WORLD,&svd);
67: SVDSetOperators(svd,A,NULL);
68: SVDSetTolerances(svd,1e-6,1000);
69: SVDSetFromOptions(svd);
70: SVDSolve(svd);
71: SVDErrorView(svd,SVD_ERROR_RELATIVE,NULL);
73: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
74: Generate the matrix of size 2*N
75: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
77: N *= 2;
78: PetscPrintf(PETSC_COMM_WORLD,"\nSingular values of a Grcar matrix, n=%" PetscInt_FMT "\n\n",N);
80: MatCreate(PETSC_COMM_WORLD,&B);
81: MatSetSizes(B,PETSC_DECIDE,PETSC_DECIDE,N,N);
82: MatSetFromOptions(B);
83: MatSetUp(B);
84: MatGetOwnershipRange(B,&Istart,&Iend);
85: for (i=Istart;i<Iend;i++) {
86: col[0]=i-1; col[1]=i; col[2]=i+1; col[3]=i+2; col[4]=i+3;
87: if (i==0) MatSetValues(B,1,&i,4,col+1,value+1,INSERT_VALUES);
88: else MatSetValues(B,1,&i,PetscMin(5,N-i+1),col,value,INSERT_VALUES);
89: }
90: MatAssemblyBegin(B,MAT_FINAL_ASSEMBLY);
91: MatAssemblyEnd(B,MAT_FINAL_ASSEMBLY);
93: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
94: Solve again, calling SVDReset() since matrix size has changed
95: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
97: SVDReset(svd); /* if this is omitted, it will be called in SVDSetOperators() */
98: SVDSetOperators(svd,B,NULL);
99: SVDSolve(svd);
100: SVDErrorView(svd,SVD_ERROR_RELATIVE,NULL);
102: /* Free work space */
103: SVDDestroy(&svd);
104: MatDestroy(&A);
105: MatDestroy(&B);
106: SlepcFinalize();
107: return 0;
108: }
110: /*TEST
112: test:
113: suffix: 1
114: args: -svd_type {{lanczos trlanczos cross cyclic lapack randomized}} -svd_nsv 3
115: requires: double
117: TEST*/