Annotation of rpl/lapack/lapack/zpotrs.f, revision 1.18
1.9 bertrand 1: *> \brief \b ZPOTRS
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 ZPOTRS + dependencies
10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/zpotrs.f">
11: *> [TGZ]</a>
12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/zpotrs.f">
13: *> [ZIP]</a>
14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zpotrs.f">
1.9 bertrand 15: *> [TXT]</a>
1.15 bertrand 16: *> \endhtmlonly
1.9 bertrand 17: *
18: * Definition:
19: * ===========
20: *
21: * SUBROUTINE ZPOTRS( 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: *> ZPOTRS solves a system of linear equations A*X = B with a Hermitian
38: *> positive definite matrix A using the Cholesky factorization
39: *> A = U**H * U or A = L * L**H computed by ZPOTRF.
40: *> \endverbatim
41: *
42: * Arguments:
43: * ==========
44: *
45: *> \param[in] UPLO
46: *> \verbatim
47: *> UPLO is CHARACTER*1
48: *> = 'U': Upper triangle of A is stored;
49: *> = 'L': Lower triangle of A is stored.
50: *> \endverbatim
51: *>
52: *> \param[in] N
53: *> \verbatim
54: *> N is INTEGER
55: *> The order of the matrix A. N >= 0.
56: *> \endverbatim
57: *>
58: *> \param[in] NRHS
59: *> \verbatim
60: *> NRHS is INTEGER
61: *> The number of right hand sides, i.e., the number of columns
62: *> of the matrix B. NRHS >= 0.
63: *> \endverbatim
64: *>
65: *> \param[in] A
66: *> \verbatim
67: *> A is COMPLEX*16 array, dimension (LDA,N)
68: *> The triangular factor U or L from the Cholesky factorization
69: *> A = U**H * U or A = L * L**H, as computed by ZPOTRF.
70: *> \endverbatim
71: *>
72: *> \param[in] LDA
73: *> \verbatim
74: *> LDA is INTEGER
75: *> The leading dimension of the array A. LDA >= max(1,N).
76: *> \endverbatim
77: *>
78: *> \param[in,out] B
79: *> \verbatim
80: *> B is COMPLEX*16 array, dimension (LDB,NRHS)
81: *> On entry, the right hand side matrix B.
82: *> On exit, the solution matrix X.
83: *> \endverbatim
84: *>
85: *> \param[in] LDB
86: *> \verbatim
87: *> LDB is INTEGER
88: *> The leading dimension of the array B. LDB >= max(1,N).
89: *> \endverbatim
90: *>
91: *> \param[out] INFO
92: *> \verbatim
93: *> INFO is INTEGER
94: *> = 0: successful exit
95: *> < 0: if INFO = -i, the i-th argument had an illegal value
96: *> \endverbatim
97: *
98: * Authors:
99: * ========
100: *
1.15 bertrand 101: *> \author Univ. of Tennessee
102: *> \author Univ. of California Berkeley
103: *> \author Univ. of Colorado Denver
104: *> \author NAG Ltd.
1.9 bertrand 105: *
106: *> \ingroup complex16POcomputational
107: *
108: * =====================================================================
1.1 bertrand 109: SUBROUTINE ZPOTRS( UPLO, N, NRHS, A, LDA, B, LDB, INFO )
110: *
1.18 ! bertrand 111: * -- LAPACK computational routine --
1.1 bertrand 112: * -- LAPACK is a software package provided by Univ. of Tennessee, --
113: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
114: *
115: * .. Scalar Arguments ..
116: CHARACTER UPLO
117: INTEGER INFO, LDA, LDB, N, NRHS
118: * ..
119: * .. Array Arguments ..
120: COMPLEX*16 A( LDA, * ), B( LDB, * )
121: * ..
122: *
123: * =====================================================================
124: *
125: * .. Parameters ..
126: COMPLEX*16 ONE
127: PARAMETER ( ONE = ( 1.0D+0, 0.0D+0 ) )
128: * ..
129: * .. Local Scalars ..
130: LOGICAL UPPER
131: * ..
132: * .. External Functions ..
133: LOGICAL LSAME
134: EXTERNAL LSAME
135: * ..
136: * .. External Subroutines ..
137: EXTERNAL XERBLA, ZTRSM
138: * ..
139: * .. Intrinsic Functions ..
140: INTRINSIC MAX
141: * ..
142: * .. Executable Statements ..
143: *
144: * Test the input parameters.
145: *
146: INFO = 0
147: UPPER = LSAME( UPLO, 'U' )
148: IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
149: INFO = -1
150: ELSE IF( N.LT.0 ) THEN
151: INFO = -2
152: ELSE IF( NRHS.LT.0 ) THEN
153: INFO = -3
154: ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
155: INFO = -5
156: ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
157: INFO = -7
158: END IF
159: IF( INFO.NE.0 ) THEN
160: CALL XERBLA( 'ZPOTRS', -INFO )
161: RETURN
162: END IF
163: *
164: * Quick return if possible
165: *
166: IF( N.EQ.0 .OR. NRHS.EQ.0 )
167: $ RETURN
168: *
169: IF( UPPER ) THEN
170: *
1.8 bertrand 171: * Solve A*X = B where A = U**H *U.
1.1 bertrand 172: *
1.8 bertrand 173: * Solve U**H *X = B, overwriting B with X.
1.1 bertrand 174: *
175: CALL ZTRSM( 'Left', 'Upper', 'Conjugate transpose', 'Non-unit',
176: $ N, NRHS, ONE, A, LDA, B, LDB )
177: *
178: * Solve U*X = B, overwriting B with X.
179: *
180: CALL ZTRSM( 'Left', 'Upper', 'No transpose', 'Non-unit', N,
181: $ NRHS, ONE, A, LDA, B, LDB )
182: ELSE
183: *
1.8 bertrand 184: * Solve A*X = B where A = L*L**H.
1.1 bertrand 185: *
186: * Solve L*X = B, overwriting B with X.
187: *
188: CALL ZTRSM( 'Left', 'Lower', 'No transpose', 'Non-unit', N,
189: $ NRHS, ONE, A, LDA, B, LDB )
190: *
1.8 bertrand 191: * Solve L**H *X = B, overwriting B with X.
1.1 bertrand 192: *
193: CALL ZTRSM( 'Left', 'Lower', 'Conjugate transpose', 'Non-unit',
194: $ N, NRHS, ONE, A, LDA, B, LDB )
195: END IF
196: *
197: RETURN
198: *
199: * End of ZPOTRS
200: *
201: END
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