GetFEM  5.4.2
gmm_precond_ildlt.h
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63 
64 #ifndef GMM_PRECOND_ILDLT_H
65 #define GMM_PRECOND_ILDLT_H
66 
67 /**@file gmm_precond_ildlt.h
68  @author Andrew Lumsdaine <[email protected]>
69  @author Lie-Quan Lee <[email protected]>
70  @author Yves Renard <[email protected]>
71  @date June 5, 2003.
72  @brief Incomplete Level 0 ILDLT Preconditioner.
73 */
74 
75 #include "gmm_precond.h"
76 
77 namespace gmm {
78 
79  /** Incomplete Level 0 LDLT Preconditioner.
80 
81  For use with symmetric real or hermitian complex sparse matrices.
82 
83  Notes: The idea under a concrete Preconditioner such as Incomplete
84  Cholesky is to create a Preconditioner object to use in iterative
85  methods.
86 
87 
88  Y. Renard : Transformed in LDLT for stability reason.
89 
90  U=LT is stored in csr format. D is stored on the diagonal of U.
91  */
92  template <typename Matrix>
93  class ildlt_precond {
94 
95  public :
96  typedef typename linalg_traits<Matrix>::value_type value_type;
97  typedef typename number_traits<value_type>::magnitude_type magnitude_type;
98  typedef csr_matrix_ref<value_type *, size_type *, size_type *, 0> tm_type;
99 
100  tm_type U;
101 
102  protected :
103  std::vector<value_type> Tri_val;
104  std::vector<size_type> Tri_ind, Tri_ptr;
105 
106  template<typename M> void do_ildlt(const M& A, row_major);
107  void do_ildlt(const Matrix& A, col_major);
108 
109  public:
110 
111  size_type nrows(void) const { return mat_nrows(U); }
112  size_type ncols(void) const { return mat_ncols(U); }
113  value_type &D(size_type i) { return Tri_val[Tri_ptr[i]]; }
114  const value_type &D(size_type i) const { return Tri_val[Tri_ptr[i]]; }
115  ildlt_precond(void) {}
116  void build_with(const Matrix& A) {
117  Tri_ptr.resize(mat_nrows(A)+1);
118  do_ildlt(A, typename principal_orientation_type<typename
119  linalg_traits<Matrix>::sub_orientation>::potype());
120  }
121  ildlt_precond(const Matrix& A) { build_with(A); }
122  size_type memsize() const {
123  return sizeof(*this) +
124  Tri_val.size() * sizeof(value_type) +
125  (Tri_ind.size()+Tri_ptr.size()) * sizeof(size_type);
126  }
127  };
128 
129  template <typename Matrix> template<typename M>
130  void ildlt_precond<Matrix>::do_ildlt(const M& A, row_major) {
131  typedef typename linalg_traits<Matrix>::storage_type store_type;
132  typedef value_type T;
133  typedef typename number_traits<T>::magnitude_type R;
134 
135  size_type Tri_loc = 0, n = mat_nrows(A), d, g, h, i, j, k;
136  if (n == 0) return;
137  T z, zz;
138  Tri_ptr[0] = 0;
139  R prec = default_tol(R());
140  R max_pivot = gmm::abs(A(0,0)) * prec;
141 
142  for (int count = 0; count < 2; ++count) {
143  if (count) { Tri_val.resize(Tri_loc); Tri_ind.resize(Tri_loc); }
144  for (Tri_loc = 0, i = 0; i < n; ++i) {
145  typedef typename linalg_traits<M>::const_sub_row_type row_type;
146  row_type row = mat_const_row(A, i);
147  typename linalg_traits<typename org_type<row_type>::t>::const_iterator
148  it = vect_const_begin(row), ite = vect_const_end(row);
149 
150  if (count) { Tri_val[Tri_loc] = T(0); Tri_ind[Tri_loc] = i; }
151  ++Tri_loc; // diagonal element
152 
153  for (k = 0; it != ite; ++it, ++k) {
154  j = index_of_it(it, k, store_type());
155  if (i == j) {
156  if (count) Tri_val[Tri_loc-1] = *it;
157  }
158  else if (j > i) {
159  if (count) { Tri_val[Tri_loc] = *it; Tri_ind[Tri_loc]=j; }
160  ++Tri_loc;
161  }
162  }
163  Tri_ptr[i+1] = Tri_loc;
164  }
165  }
166 
167  if (A(0,0) == T(0)) {
168  Tri_val[Tri_ptr[0]] = T(1);
169  GMM_WARNING2("pivot 0 is too small");
170  }
171 
172  for (k = 0; k < n; k++) {
173  d = Tri_ptr[k];
174  z = T(gmm::real(Tri_val[d])); Tri_val[d] = z;
175  if (gmm::abs(z) <= max_pivot) {
176  Tri_val[d] = z = T(1);
177  GMM_WARNING2("pivot " << k << " is too small [" << gmm::abs(z) << "]");
178  }
179  max_pivot = std::max(max_pivot, std::min(gmm::abs(z) * prec, R(1)));
180 
181  for (i = d + 1; i < Tri_ptr[k+1]; ++i) Tri_val[i] /= z;
182  for (i = d + 1; i < Tri_ptr[k+1]; ++i) {
183  zz = gmm::conj(Tri_val[i] * z);
184  h = Tri_ind[i];
185  g = i;
186 
187  for (j = Tri_ptr[h] ; j < Tri_ptr[h+1]; ++j)
188  for ( ; g < Tri_ptr[k+1] && Tri_ind[g] <= Tri_ind[j]; ++g)
189  if (Tri_ind[g] == Tri_ind[j])
190  Tri_val[j] -= zz * Tri_val[g];
191  }
192  }
193  U = tm_type(&(Tri_val[0]), &(Tri_ind[0]), &(Tri_ptr[0]),
194  n, mat_ncols(A));
195  }
196 
197  template <typename Matrix>
198  void ildlt_precond<Matrix>::do_ildlt(const Matrix& A, col_major)
199  { do_ildlt(gmm::conjugated(A), row_major()); }
200 
201  template <typename Matrix, typename V1, typename V2> inline
202  void mult(const ildlt_precond<Matrix>& P, const V1 &v1, V2 &v2) {
203  gmm::copy(v1, v2);
204  gmm::lower_tri_solve(gmm::conjugated(P.U), v2, true);
205  for (size_type i = 0; i < mat_nrows(P.U); ++i) v2[i] /= P.D(i);
206  gmm::upper_tri_solve(P.U, v2, true);
207  }
208 
209  template <typename Matrix, typename V1, typename V2> inline
210  void transposed_mult(const ildlt_precond<Matrix>& P,const V1 &v1,V2 &v2)
211  { mult(P, v1, v2); }
212 
213  template <typename Matrix, typename V1, typename V2> inline
214  void left_mult(const ildlt_precond<Matrix>& P, const V1 &v1, V2 &v2) {
215  copy(v1, v2);
216  gmm::lower_tri_solve(gmm::conjugated(P.U), v2, true);
217  for (size_type i = 0; i < mat_nrows(P.U); ++i) v2[i] /= P.D(i);
218  }
219 
220  template <typename Matrix, typename V1, typename V2> inline
221  void right_mult(const ildlt_precond<Matrix>& P, const V1 &v1, V2 &v2)
222  { copy(v1, v2); gmm::upper_tri_solve(P.U, v2, true); }
223 
224  template <typename Matrix, typename V1, typename V2> inline
225  void transposed_left_mult(const ildlt_precond<Matrix>& P, const V1 &v1,
226  V2 &v2) {
227  copy(v1, v2);
228  gmm::upper_tri_solve(P.U, v2, true);
229  for (size_type i = 0; i < mat_nrows(P.U); ++i) v2[i] /= P.D(i);
230  }
231 
232  template <typename Matrix, typename V1, typename V2> inline
233  void transposed_right_mult(const ildlt_precond<Matrix>& P, const V1 &v1,
234  V2 &v2)
235  { copy(v1, v2); gmm::lower_tri_solve(gmm::conjugated(P.U), v2, true); }
236 
237 
238 }
239 
240 #endif
241 
gmm::ildlt_precond
Incomplete Level 0 LDLT Preconditioner.
Definition: gmm_precond_ildlt.h:93
bgeot::size_type
size_t size_type
used as the common size type in the library
Definition: bgeot_poly.h:49
gmm_precond.h
gmm preconditioners.
gmm::copy
void copy(const L1 &l1, L2 &l2)
*‍/
Definition: gmm_blas.h:977