Annotation of rpl/lapack/lapack/zposv.f, revision 1.18
1.9 bertrand 1: *> \brief <b> ZPOSV computes the solution to system of linear equations A * X = B for PO matrices</b>
2: *
3: * =========== DOCUMENTATION ===========
4: *
1.15 bertrand 5: * Online html documentation available at
6: * http://www.netlib.org/lapack/explore-html/
1.9 bertrand 7: *
8: *> \htmlonly
1.15 bertrand 9: *> Download ZPOSV + dependencies
10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/zposv.f">
11: *> [TGZ]</a>
12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/zposv.f">
13: *> [ZIP]</a>
14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zposv.f">
1.9 bertrand 15: *> [TXT]</a>
1.15 bertrand 16: *> \endhtmlonly
1.9 bertrand 17: *
18: * Definition:
19: * ===========
20: *
21: * SUBROUTINE ZPOSV( UPLO, N, NRHS, A, LDA, B, LDB, INFO )
1.15 bertrand 22: *
1.9 bertrand 23: * .. Scalar Arguments ..
24: * CHARACTER UPLO
25: * INTEGER INFO, LDA, LDB, N, NRHS
26: * ..
27: * .. Array Arguments ..
28: * COMPLEX*16 A( LDA, * ), B( LDB, * )
29: * ..
1.15 bertrand 30: *
1.9 bertrand 31: *
32: *> \par Purpose:
33: * =============
34: *>
35: *> \verbatim
36: *>
37: *> ZPOSV computes the solution to a complex system of linear equations
38: *> A * X = B,
39: *> where A is an N-by-N Hermitian positive definite matrix and X and B
40: *> are N-by-NRHS matrices.
41: *>
42: *> The Cholesky decomposition is used to factor A as
43: *> A = U**H* U, if UPLO = 'U', or
44: *> A = L * L**H, if UPLO = 'L',
45: *> where U is an upper triangular matrix and L is a lower triangular
46: *> matrix. The factored form of A is then used to solve the system of
47: *> equations A * X = B.
48: *> \endverbatim
49: *
50: * Arguments:
51: * ==========
52: *
53: *> \param[in] UPLO
54: *> \verbatim
55: *> UPLO is CHARACTER*1
56: *> = 'U': Upper triangle of A is stored;
57: *> = 'L': Lower triangle of A is stored.
58: *> \endverbatim
59: *>
60: *> \param[in] N
61: *> \verbatim
62: *> N is INTEGER
63: *> The number of linear equations, i.e., the order of the
64: *> matrix A. N >= 0.
65: *> \endverbatim
66: *>
67: *> \param[in] NRHS
68: *> \verbatim
69: *> NRHS is INTEGER
70: *> The number of right hand sides, i.e., the number of columns
71: *> of the matrix B. NRHS >= 0.
72: *> \endverbatim
73: *>
74: *> \param[in,out] A
75: *> \verbatim
76: *> A is COMPLEX*16 array, dimension (LDA,N)
77: *> On entry, the Hermitian matrix A. If UPLO = 'U', the leading
78: *> N-by-N upper triangular part of A contains the upper
79: *> triangular part of the matrix A, and the strictly lower
80: *> triangular part of A is not referenced. If UPLO = 'L', the
81: *> leading N-by-N lower triangular part of A contains the lower
82: *> triangular part of the matrix A, and the strictly upper
83: *> triangular part of A is not referenced.
84: *>
85: *> On exit, if INFO = 0, the factor U or L from the Cholesky
86: *> factorization A = U**H *U or A = L*L**H.
87: *> \endverbatim
88: *>
89: *> \param[in] LDA
90: *> \verbatim
91: *> LDA is INTEGER
92: *> The leading dimension of the array A. LDA >= max(1,N).
93: *> \endverbatim
94: *>
95: *> \param[in,out] B
96: *> \verbatim
97: *> B is COMPLEX*16 array, dimension (LDB,NRHS)
98: *> On entry, the N-by-NRHS right hand side matrix B.
99: *> On exit, if INFO = 0, the N-by-NRHS solution matrix X.
100: *> \endverbatim
101: *>
102: *> \param[in] LDB
103: *> \verbatim
104: *> LDB is INTEGER
105: *> The leading dimension of the array B. LDB >= max(1,N).
106: *> \endverbatim
107: *>
108: *> \param[out] INFO
109: *> \verbatim
110: *> INFO is INTEGER
111: *> = 0: successful exit
112: *> < 0: if INFO = -i, the i-th argument had an illegal value
113: *> > 0: if INFO = i, the leading minor of order i of A is not
114: *> positive definite, so the factorization could not be
115: *> completed, and the solution has not been computed.
116: *> \endverbatim
117: *
118: * Authors:
119: * ========
120: *
1.15 bertrand 121: *> \author Univ. of Tennessee
122: *> \author Univ. of California Berkeley
123: *> \author Univ. of Colorado Denver
124: *> \author NAG Ltd.
1.9 bertrand 125: *
126: *> \ingroup complex16POsolve
127: *
128: * =====================================================================
1.1 bertrand 129: SUBROUTINE ZPOSV( UPLO, N, NRHS, A, LDA, B, LDB, INFO )
130: *
1.18 ! bertrand 131: * -- LAPACK driver routine --
1.1 bertrand 132: * -- LAPACK is a software package provided by Univ. of Tennessee, --
133: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
134: *
135: * .. Scalar Arguments ..
136: CHARACTER UPLO
137: INTEGER INFO, LDA, LDB, N, NRHS
138: * ..
139: * .. Array Arguments ..
140: COMPLEX*16 A( LDA, * ), B( LDB, * )
141: * ..
142: *
143: * =====================================================================
144: *
145: * .. External Functions ..
146: LOGICAL LSAME
147: EXTERNAL LSAME
148: * ..
149: * .. External Subroutines ..
150: EXTERNAL XERBLA, ZPOTRF, ZPOTRS
151: * ..
152: * .. Intrinsic Functions ..
153: INTRINSIC MAX
154: * ..
155: * .. Executable Statements ..
156: *
157: * Test the input parameters.
158: *
159: INFO = 0
160: IF( .NOT.LSAME( UPLO, 'U' ) .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
161: INFO = -1
162: ELSE IF( N.LT.0 ) THEN
163: INFO = -2
164: ELSE IF( NRHS.LT.0 ) THEN
165: INFO = -3
166: ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
167: INFO = -5
168: ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
169: INFO = -7
170: END IF
171: IF( INFO.NE.0 ) THEN
172: CALL XERBLA( 'ZPOSV ', -INFO )
173: RETURN
174: END IF
175: *
1.8 bertrand 176: * Compute the Cholesky factorization A = U**H *U or A = L*L**H.
1.1 bertrand 177: *
178: CALL ZPOTRF( UPLO, N, A, LDA, INFO )
179: IF( INFO.EQ.0 ) THEN
180: *
181: * Solve the system A*X = B, overwriting B with X.
182: *
183: CALL ZPOTRS( UPLO, N, NRHS, A, LDA, B, LDB, INFO )
184: *
185: END IF
186: RETURN
187: *
188: * End of ZPOSV
189: *
190: END
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