Actual source code: test3.c
slepc-3.7.1 2016-05-27
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[] = "Test SVD with user-provided initial vectors.\n\n"
23: "The command line options are:\n"
24: " -n <n>, where <n> = row dimension.\n"
25: " -m <m>, where <m> = column dimension.\n\n";
27: #include <slepcsvd.h>
29: /*
30: This example computes the singular values of a rectangular nxm Grcar matrix:
32: | 1 1 1 1 |
33: | -1 1 1 1 1 |
34: | -1 1 1 1 1 |
35: A = | . . . . . |
36: | . . . . . |
37: | -1 1 1 1 1 |
38: | -1 1 1 1 |
40: */
44: int main(int argc,char **argv)
45: {
46: Mat A; /* Grcar matrix */
47: SVD svd; /* singular value solver context */
48: Vec v0,w0; /* initial vectors */
49: PetscInt N=35,M=30,Istart,Iend,i,col[5];
50: PetscScalar value[] = { -1, 1, 1, 1, 1 };
53: SlepcInitialize(&argc,&argv,(char*)0,help);
54: PetscOptionsGetInt(NULL,NULL,"-n",&N,NULL);
55: PetscOptionsGetInt(NULL,NULL,"-m",&M,NULL);
56: PetscPrintf(PETSC_COMM_WORLD,"\nSVD of a rectangular Grcar matrix, %Dx%D\n\n",N,M);
58: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
59: Generate the matrix
60: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
62: MatCreate(PETSC_COMM_WORLD,&A);
63: MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,M);
64: MatSetFromOptions(A);
65: MatSetUp(A);
67: MatGetOwnershipRange(A,&Istart,&Iend);
68: for (i=Istart;i<Iend;i++) {
69: col[0]=i-1; col[1]=i; col[2]=i+1; col[3]=i+2; col[4]=i+3;
70: if (i==0) {
71: MatSetValues(A,1,&i,PetscMin(4,M-i+1),col+1,value+1,INSERT_VALUES);
72: } else {
73: MatSetValues(A,1,&i,PetscMin(5,M-i+1),col,value,INSERT_VALUES);
74: }
75: }
76: MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
77: MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
79: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
80: Create the SVD context and solve the problem
81: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
83: SVDCreate(PETSC_COMM_WORLD,&svd);
84: SVDSetOperator(svd,A);
85: SVDSetFromOptions(svd);
87: /*
88: Set the initial vectors. This is optional, if not done the initial
89: vectors are set to random values
90: */
91: MatCreateVecs(A,&v0,&w0);
92: VecSet(v0,1.0);
93: VecSet(w0,1.0);
94: SVDSetInitialSpace(svd,1,&v0);
95: SVDSetInitialSpaceLeft(svd,1,&w0);
97: /*
98: Compute solution
99: */
100: SVDSolve(svd);
101: SVDErrorView(svd,SVD_ERROR_RELATIVE,NULL);
103: /*
104: Free work space
105: */
106: VecDestroy(&v0);
107: VecDestroy(&w0);
108: SVDDestroy(&svd);
109: MatDestroy(&A);
110: SlepcFinalize();
111: return ierr;
112: }