LAPACK  3.10.1 LAPACK: Linear Algebra PACKage
chesv_aa_2stage.f
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1 *> \brief <b> CHESV_AA_2STAGE computes the solution to system of linear equations A * X = B for HE matrices</b>
2 *
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17 *
18 * Definition:
19 * ===========
20 *
21 * SUBROUTINE CHESV_AA_2STAGE( UPLO, N, NRHS, A, LDA, TB, LTB,
22 * IPIV, IPIV2, B, LDB, WORK, LWORK,
23 * INFO )
24 *
25 * .. Scalar Arguments ..
26 * CHARACTER UPLO
27 * INTEGER N, NRHS, LDA, LTB, LDB, LWORK, INFO
28 * ..
29 * .. Array Arguments ..
30 * INTEGER IPIV( * ), IPIV2( * )
31 * COMPLEX A( LDA, * ), TB( * ), B( LDB, *), WORK( * )
32 * ..
33 *
34 *> \par Purpose:
35 * =============
36 *>
37 *> \verbatim
38 *>
39 *> CHESV_AA_2STAGE computes the solution to a complex system of
40 *> linear equations
41 *> A * X = B,
42 *> where A is an N-by-N Hermitian matrix and X and B are N-by-NRHS
43 *> matrices.
44 *>
45 *> Aasen's 2-stage algorithm is used to factor A as
46 *> A = U**H * T * U, if UPLO = 'U', or
47 *> A = L * T * L**H, if UPLO = 'L',
48 *> where U (or L) is a product of permutation and unit upper (lower)
49 *> triangular matrices, and T is Hermitian and band. The matrix T is
50 *> then LU-factored with partial pivoting. The factored form of A
51 *> is then used to solve the system of equations A * X = B.
52 *>
53 *> This is the blocked version of the algorithm, calling Level 3 BLAS.
54 *> \endverbatim
55 *
56 * Arguments:
57 * ==========
58 *
59 *> \param[in] UPLO
60 *> \verbatim
61 *> UPLO is CHARACTER*1
62 *> = 'U': Upper triangle of A is stored;
63 *> = 'L': Lower triangle of A is stored.
64 *> \endverbatim
65 *>
66 *> \param[in] N
67 *> \verbatim
68 *> N is INTEGER
69 *> The order of the matrix A. N >= 0.
70 *> \endverbatim
71 *>
72 *> \param[in] NRHS
73 *> \verbatim
74 *> NRHS is INTEGER
75 *> The number of right hand sides, i.e., the number of columns
76 *> of the matrix B. NRHS >= 0.
77 *> \endverbatim
78 *>
79 *> \param[in,out] A
80 *> \verbatim
81 *> A is COMPLEX array, dimension (LDA,N)
82 *> On entry, the hermitian matrix A. If UPLO = 'U', the leading
83 *> N-by-N upper triangular part of A contains the upper
84 *> triangular part of the matrix A, and the strictly lower
85 *> triangular part of A is not referenced. If UPLO = 'L', the
86 *> leading N-by-N lower triangular part of A contains the lower
87 *> triangular part of the matrix A, and the strictly upper
88 *> triangular part of A is not referenced.
89 *>
90 *> On exit, L is stored below (or above) the subdiaonal blocks,
91 *> when UPLO is 'L' (or 'U').
92 *> \endverbatim
93 *>
94 *> \param[in] LDA
95 *> \verbatim
96 *> LDA is INTEGER
97 *> The leading dimension of the array A. LDA >= max(1,N).
98 *> \endverbatim
99 *>
100 *> \param[out] TB
101 *> \verbatim
102 *> TB is COMPLEX array, dimension (LTB)
103 *> On exit, details of the LU factorization of the band matrix.
104 *> \endverbatim
105 *>
106 *> \param[in] LTB
107 *> \verbatim
108 *> LTB is INTEGER
109 *> The size of the array TB. LTB >= 4*N, internally
110 *> used to select NB such that LTB >= (3*NB+1)*N.
111 *>
112 *> If LTB = -1, then a workspace query is assumed; the
113 *> routine only calculates the optimal size of LTB,
114 *> returns this value as the first entry of TB, and
115 *> no error message related to LTB is issued by XERBLA.
116 *> \endverbatim
117 *>
118 *> \param[out] IPIV
119 *> \verbatim
120 *> IPIV is INTEGER array, dimension (N)
121 *> On exit, it contains the details of the interchanges, i.e.,
122 *> the row and column k of A were interchanged with the
123 *> row and column IPIV(k).
124 *> \endverbatim
125 *>
126 *> \param[out] IPIV2
127 *> \verbatim
128 *> IPIV2 is INTEGER array, dimension (N)
129 *> On exit, it contains the details of the interchanges, i.e.,
130 *> the row and column k of T were interchanged with the
131 *> row and column IPIV(k).
132 *> \endverbatim
133 *>
134 *> \param[in,out] B
135 *> \verbatim
136 *> B is COMPLEX array, dimension (LDB,NRHS)
137 *> On entry, the right hand side matrix B.
138 *> On exit, the solution matrix X.
139 *> \endverbatim
140 *>
141 *> \param[in] LDB
142 *> \verbatim
143 *> LDB is INTEGER
144 *> The leading dimension of the array B. LDB >= max(1,N).
145 *> \endverbatim
146 *>
147 *> \param[out] WORK
148 *> \verbatim
149 *> WORK is COMPLEX workspace of size LWORK
150 *> \endverbatim
151 *>
152 *> \param[in] LWORK
153 *> \verbatim
154 *> LWORK is INTEGER
155 *> The size of WORK. LWORK >= N, internally used to select NB
156 *> such that LWORK >= N*NB.
157 *>
158 *> If LWORK = -1, then a workspace query is assumed; the
159 *> routine only calculates the optimal size of the WORK array,
160 *> returns this value as the first entry of the WORK array, and
161 *> no error message related to LWORK is issued by XERBLA.
162 *> \endverbatim
163 *>
164 *> \param[out] INFO
165 *> \verbatim
166 *> INFO is INTEGER
167 *> = 0: successful exit
168 *> < 0: if INFO = -i, the i-th argument had an illegal value.
169 *> > 0: if INFO = i, band LU factorization failed on i-th column
170 *> \endverbatim
171 *
172 * Authors:
173 * ========
174 *
175 *> \author Univ. of Tennessee
176 *> \author Univ. of California Berkeley
177 *> \author Univ. of Colorado Denver
178 *> \author NAG Ltd.
179 *
180 *> \ingroup complexSYcomputational
181 *
182 * =====================================================================
183  SUBROUTINE chesv_aa_2stage( UPLO, N, NRHS, A, LDA, TB, LTB,
184  \$ IPIV, IPIV2, B, LDB, WORK, LWORK,
185  \$ INFO )
186 *
187 * -- LAPACK computational routine --
188 * -- LAPACK is a software package provided by Univ. of Tennessee, --
189 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
190 *
191  IMPLICIT NONE
192 *
193 * .. Scalar Arguments ..
194  CHARACTER UPLO
195  INTEGER N, NRHS, LDA, LDB, LTB, LWORK, INFO
196 * ..
197 * .. Array Arguments ..
198  INTEGER IPIV( * ), IPIV2( * )
199  COMPLEX A( LDA, * ), B( LDB, * ), TB( * ), WORK( * )
200 * ..
201 *
202 * =====================================================================
203 *
204 * .. Local Scalars ..
205  LOGICAL UPPER, TQUERY, WQUERY
206  INTEGER LWKOPT
207 * ..
208 * .. External Functions ..
209  LOGICAL LSAME
210  EXTERNAL LSAME
211 * ..
212 * .. External Subroutines ..
214  \$ xerbla
215 * ..
216 * .. Intrinsic Functions ..
217  INTRINSIC max
218 * ..
219 * .. Executable Statements ..
220 *
221 * Test the input parameters.
222 *
223  info = 0
224  upper = lsame( uplo, 'U' )
225  wquery = ( lwork.EQ.-1 )
226  tquery = ( ltb.EQ.-1 )
227  IF( .NOT.upper .AND. .NOT.lsame( uplo, 'L' ) ) THEN
228  info = -1
229  ELSE IF( n.LT.0 ) THEN
230  info = -2
231  ELSE IF( nrhs.LT.0 ) THEN
232  info = -3
233  ELSE IF( lda.LT.max( 1, n ) ) THEN
234  info = -5
235  ELSE IF( ltb.LT.( 4*n ) .AND. .NOT.tquery ) THEN
236  info = -7
237  ELSE IF( ldb.LT.max( 1, n ) ) THEN
238  info = -11
239  ELSE IF( lwork.LT.n .AND. .NOT.wquery ) THEN
240  info = -13
241  END IF
242 *
243  IF( info.EQ.0 ) THEN
244  CALL chetrf_aa_2stage( uplo, n, a, lda, tb, -1, ipiv,
245  \$ ipiv2, work, -1, info )
246  lwkopt = int( work(1) )
247  END IF
248 *
249  IF( info.NE.0 ) THEN
250  CALL xerbla( 'CHESV_AA_2STAGE', -info )
251  RETURN
252  ELSE IF( wquery .OR. tquery ) THEN
253  RETURN
254  END IF
255 *
256 *
257 * Compute the factorization A = U**H*T*U or A = L*T*L**H.
258 *
259  CALL chetrf_aa_2stage( uplo, n, a, lda, tb, ltb, ipiv, ipiv2,
260  \$ work, lwork, info )
261  IF( info.EQ.0 ) THEN
262 *
263 * Solve the system A*X = B, overwriting B with X.
264 *
265  CALL chetrs_aa_2stage( uplo, n, nrhs, a, lda, tb, ltb, ipiv,
266  \$ ipiv2, b, ldb, info )
267 *
268  END IF
269 *
270  work( 1 ) = lwkopt
271 *
272  RETURN
273 *
274 * End of CHESV_AA_2STAGE
275 *
276  END
subroutine xerbla(SRNAME, INFO)
XERBLA
Definition: xerbla.f:60
subroutine chetrf_aa_2stage(UPLO, N, A, LDA, TB, LTB, IPIV, IPIV2, WORK, LWORK, INFO)
CHETRF_AA_2STAGE
subroutine chesv_aa_2stage(UPLO, N, NRHS, A, LDA, TB, LTB, IPIV, IPIV2, B, LDB, WORK, LWORK, INFO)
CHESV_AA_2STAGE computes the solution to system of linear equations A * X = B for HE matrices
subroutine chetrs_aa_2stage(UPLO, N, NRHS, A, LDA, TB, LTB, IPIV, IPIV2, B, LDB, INFO)
CHETRS_AA_2STAGE