2329
|
1 SUBROUTINE ZGETRS( TRANS, N, NRHS, A, LDA, IPIV, B, LDB, INFO ) |
|
2 * |
7034
|
3 * -- LAPACK routine (version 3.1) -- |
|
4 * Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. |
|
5 * November 2006 |
2329
|
6 * |
|
7 * .. Scalar Arguments .. |
|
8 CHARACTER TRANS |
|
9 INTEGER INFO, LDA, LDB, N, NRHS |
|
10 * .. |
|
11 * .. Array Arguments .. |
|
12 INTEGER IPIV( * ) |
|
13 COMPLEX*16 A( LDA, * ), B( LDB, * ) |
|
14 * .. |
|
15 * |
|
16 * Purpose |
|
17 * ======= |
|
18 * |
|
19 * ZGETRS solves a system of linear equations |
|
20 * A * X = B, A**T * X = B, or A**H * X = B |
|
21 * with a general N-by-N matrix A using the LU factorization computed |
|
22 * by ZGETRF. |
|
23 * |
|
24 * Arguments |
|
25 * ========= |
|
26 * |
|
27 * TRANS (input) CHARACTER*1 |
|
28 * Specifies the form of the system of equations: |
|
29 * = 'N': A * X = B (No transpose) |
|
30 * = 'T': A**T * X = B (Transpose) |
|
31 * = 'C': A**H * X = B (Conjugate transpose) |
|
32 * |
|
33 * N (input) INTEGER |
|
34 * The order of the matrix A. N >= 0. |
|
35 * |
|
36 * NRHS (input) INTEGER |
|
37 * The number of right hand sides, i.e., the number of columns |
|
38 * of the matrix B. NRHS >= 0. |
|
39 * |
|
40 * A (input) COMPLEX*16 array, dimension (LDA,N) |
|
41 * The factors L and U from the factorization A = P*L*U |
|
42 * as computed by ZGETRF. |
|
43 * |
|
44 * LDA (input) INTEGER |
|
45 * The leading dimension of the array A. LDA >= max(1,N). |
|
46 * |
|
47 * IPIV (input) INTEGER array, dimension (N) |
|
48 * The pivot indices from ZGETRF; for 1<=i<=N, row i of the |
|
49 * matrix was interchanged with row IPIV(i). |
|
50 * |
|
51 * B (input/output) COMPLEX*16 array, dimension (LDB,NRHS) |
|
52 * On entry, the right hand side matrix B. |
|
53 * On exit, the solution matrix X. |
|
54 * |
|
55 * LDB (input) INTEGER |
|
56 * The leading dimension of the array B. LDB >= max(1,N). |
|
57 * |
|
58 * INFO (output) INTEGER |
|
59 * = 0: successful exit |
|
60 * < 0: if INFO = -i, the i-th argument had an illegal value |
|
61 * |
|
62 * ===================================================================== |
|
63 * |
|
64 * .. Parameters .. |
|
65 COMPLEX*16 ONE |
|
66 PARAMETER ( ONE = ( 1.0D+0, 0.0D+0 ) ) |
|
67 * .. |
|
68 * .. Local Scalars .. |
|
69 LOGICAL NOTRAN |
|
70 * .. |
|
71 * .. External Functions .. |
|
72 LOGICAL LSAME |
|
73 EXTERNAL LSAME |
|
74 * .. |
|
75 * .. External Subroutines .. |
|
76 EXTERNAL XERBLA, ZLASWP, ZTRSM |
|
77 * .. |
|
78 * .. Intrinsic Functions .. |
|
79 INTRINSIC MAX |
|
80 * .. |
|
81 * .. Executable Statements .. |
|
82 * |
|
83 * Test the input parameters. |
|
84 * |
|
85 INFO = 0 |
|
86 NOTRAN = LSAME( TRANS, 'N' ) |
|
87 IF( .NOT.NOTRAN .AND. .NOT.LSAME( TRANS, 'T' ) .AND. .NOT. |
|
88 $ LSAME( TRANS, 'C' ) ) THEN |
|
89 INFO = -1 |
|
90 ELSE IF( N.LT.0 ) THEN |
|
91 INFO = -2 |
|
92 ELSE IF( NRHS.LT.0 ) THEN |
|
93 INFO = -3 |
|
94 ELSE IF( LDA.LT.MAX( 1, N ) ) THEN |
|
95 INFO = -5 |
|
96 ELSE IF( LDB.LT.MAX( 1, N ) ) THEN |
|
97 INFO = -8 |
|
98 END IF |
|
99 IF( INFO.NE.0 ) THEN |
|
100 CALL XERBLA( 'ZGETRS', -INFO ) |
|
101 RETURN |
|
102 END IF |
|
103 * |
|
104 * Quick return if possible |
|
105 * |
|
106 IF( N.EQ.0 .OR. NRHS.EQ.0 ) |
|
107 $ RETURN |
|
108 * |
|
109 IF( NOTRAN ) THEN |
|
110 * |
|
111 * Solve A * X = B. |
|
112 * |
|
113 * Apply row interchanges to the right hand sides. |
|
114 * |
|
115 CALL ZLASWP( NRHS, B, LDB, 1, N, IPIV, 1 ) |
|
116 * |
|
117 * Solve L*X = B, overwriting B with X. |
|
118 * |
|
119 CALL ZTRSM( 'Left', 'Lower', 'No transpose', 'Unit', N, NRHS, |
|
120 $ ONE, A, LDA, B, LDB ) |
|
121 * |
|
122 * Solve U*X = B, overwriting B with X. |
|
123 * |
|
124 CALL ZTRSM( 'Left', 'Upper', 'No transpose', 'Non-unit', N, |
|
125 $ NRHS, ONE, A, LDA, B, LDB ) |
|
126 ELSE |
|
127 * |
|
128 * Solve A**T * X = B or A**H * X = B. |
|
129 * |
|
130 * Solve U'*X = B, overwriting B with X. |
|
131 * |
|
132 CALL ZTRSM( 'Left', 'Upper', TRANS, 'Non-unit', N, NRHS, ONE, |
|
133 $ A, LDA, B, LDB ) |
|
134 * |
|
135 * Solve L'*X = B, overwriting B with X. |
|
136 * |
|
137 CALL ZTRSM( 'Left', 'Lower', TRANS, 'Unit', N, NRHS, ONE, A, |
|
138 $ LDA, B, LDB ) |
|
139 * |
|
140 * Apply row interchanges to the solution vectors. |
|
141 * |
|
142 CALL ZLASWP( NRHS, B, LDB, 1, N, IPIV, -1 ) |
|
143 END IF |
|
144 * |
|
145 RETURN |
|
146 * |
|
147 * End of ZGETRS |
|
148 * |
|
149 END |