2 choleski.cc -- implement Choleski_decomposition
4 source file of the Flower Library
6 (c) 1997 Han-Wen Nienhuys <hanwen@stack.nl>
10 const Real EPS = 1e-7; // so sue me. Hard coded
12 // for testing new Matrix_storage.
16 Choleski_decomposition::solve(Vector rhs)const
22 // forward substitution
23 for (int i=0; i < n; i++) {
25 for (int j=0; j < i; j++)
27 y(i) = (rhs(i) - sum)/L(i,i);
29 for (int i=0; i < n; i++)
33 Vector &x(rhs); // using input as return val.
34 for (int i=n-1; i >= 0; i--) {
36 for (int j=i+1; j < n; j++)
38 x(i) = (y(i) - sum)/L(i,i);
44 Choleski_decomposition::full_matrix_decompose(Matrix const & P)
49 for (int k= 0; k < n; k++) {
50 for (int j = 0; j < k; j++){
52 for (int l=0; l < j; l++)
53 sum += L(k,l)*L(j,l)*D(l);
54 L(k,j) = (P(k,j) - sum)/D(j);
58 for (int l=0; l < k; l++)
59 sum += sqr(L(k,l))*D(l);
60 Real d = P(k,k) - sum;
67 Choleski_decomposition::band_matrix_decompose(Matrix const &P)
73 for (int i= 0; i < n; i++) {
74 for (int j = 0 >? i - b; j < i; j++){
76 for (int l=0 >? i - b; l < j; l++)
77 sum += L(i,l)*L(j,l)*D(l);
78 L(i,j) = (P(i,j) - sum)/D(j);
82 for (int l=0 >? i - b; l < i; l++)
83 sum += sqr(L(i,l))*D(l);
84 Real d = P(i,i) - sum;
88 assert ( L.band_i() == P.band_i());
95 Standard matrix algorithm.
98 Choleski_decomposition::Choleski_decomposition(Matrix const & P)
99 : L(P.dim()), D(P.dim())
102 assert((P-P.transposed()).norm()/P.norm() < EPS);
105 band_matrix_decompose(P);
107 full_matrix_decompose(P);
111 assert((original()-P).norm() / P.norm() < EPS);
116 Choleski_decomposition::original() const
120 return L*T*L.transposed();
124 Choleski_decomposition::inverse() const
129 for (int i = 0; i < n; i++) {
131 Vector inv(solve(e_i));
132 for (int j = 0 ; j<n; j++)
137 Matrix I1(n), I2(original());
139 assert((I1-I2*invm).norm()/I2.norm() < EPS);