Actual source code: test9.c
slepc-3.17.2 2022-08-09
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 };
40: SlepcInitialize(&argc,&argv,(char*)0,help);
41: PetscOptionsGetInt(NULL,NULL,"-n",&N,NULL);
42: PetscPrintf(PETSC_COMM_WORLD,"\nSingular values of a Grcar matrix, n=%" PetscInt_FMT "\n\n",N);
44: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
45: Generate the matrix of size N
46: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
48: MatCreate(PETSC_COMM_WORLD,&A);
49: MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,N);
50: MatSetFromOptions(A);
51: MatSetUp(A);
52: MatGetOwnershipRange(A,&Istart,&Iend);
53: for (i=Istart;i<Iend;i++) {
54: col[0]=i-1; col[1]=i; col[2]=i+1; col[3]=i+2; col[4]=i+3;
55: if (i==0) MatSetValues(A,1,&i,4,col+1,value+1,INSERT_VALUES);
56: else MatSetValues(A,1,&i,PetscMin(5,N-i+1),col,value,INSERT_VALUES);
57: }
58: MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
59: MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
61: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
62: Create the singular value solver, set options and solve
63: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
65: SVDCreate(PETSC_COMM_WORLD,&svd);
66: SVDSetOperators(svd,A,NULL);
67: SVDSetTolerances(svd,1e-6,1000);
68: SVDSetFromOptions(svd);
69: SVDSolve(svd);
70: SVDErrorView(svd,SVD_ERROR_RELATIVE,NULL);
72: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
73: Generate the matrix of size 2*N
74: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
76: N *= 2;
77: PetscPrintf(PETSC_COMM_WORLD,"\nSingular values of a Grcar matrix, n=%" PetscInt_FMT "\n\n",N);
79: MatCreate(PETSC_COMM_WORLD,&B);
80: MatSetSizes(B,PETSC_DECIDE,PETSC_DECIDE,N,N);
81: MatSetFromOptions(B);
82: MatSetUp(B);
83: MatGetOwnershipRange(B,&Istart,&Iend);
84: for (i=Istart;i<Iend;i++) {
85: col[0]=i-1; col[1]=i; col[2]=i+1; col[3]=i+2; col[4]=i+3;
86: if (i==0) MatSetValues(B,1,&i,4,col+1,value+1,INSERT_VALUES);
87: else MatSetValues(B,1,&i,PetscMin(5,N-i+1),col,value,INSERT_VALUES);
88: }
89: MatAssemblyBegin(B,MAT_FINAL_ASSEMBLY);
90: MatAssemblyEnd(B,MAT_FINAL_ASSEMBLY);
92: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
93: Solve again, calling SVDReset() since matrix size has changed
94: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
96: SVDReset(svd); /* if this is omitted, it will be called in SVDSetOperators() */
97: SVDSetOperators(svd,B,NULL);
98: SVDSolve(svd);
99: SVDErrorView(svd,SVD_ERROR_RELATIVE,NULL);
101: /* Free work space */
102: SVDDestroy(&svd);
103: MatDestroy(&A);
104: MatDestroy(&B);
105: SlepcFinalize();
106: return 0;
107: }
109: /*TEST
111: test:
112: suffix: 1
113: args: -svd_type {{lanczos trlanczos cross cyclic lapack randomized}} -svd_nsv 3
114: requires: double
116: TEST*/