1 /* ./src_f77/cpbsv.f -- translated by f2c (version 20030320).
2 You must link the resulting object file with the libraries:
3 -lf2c -lm (in that order)
4 */
5
6 #include <punc/vf2c.h>
7
cpbsv_(char * uplo,integer * n,integer * kd,integer * nrhs,complex * ab,integer * ldab,complex * b,integer * ldb,integer * info,ftnlen uplo_len)8 /* Subroutine */ int cpbsv_(char *uplo, integer *n, integer *kd, integer *
9 nrhs, complex *ab, integer *ldab, complex *b, integer *ldb, integer *
10 info, ftnlen uplo_len)
11 {
12 /* System generated locals */
13 integer ab_dim1, ab_offset, b_dim1, b_offset, i__1;
14
15 /* Local variables */
16 extern logical lsame_(char *, char *, ftnlen, ftnlen);
17 extern /* Subroutine */ int xerbla_(char *, integer *, ftnlen), cpbtrf_(
18 char *, integer *, integer *, complex *, integer *, integer *,
19 ftnlen), cpbtrs_(char *, integer *, integer *, integer *, complex
20 *, integer *, complex *, integer *, integer *, ftnlen);
21
22
23 /* -- LAPACK driver routine (version 3.0) -- */
24 /* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., */
25 /* Courant Institute, Argonne National Lab, and Rice University */
26 /* March 31, 1993 */
27
28 /* .. Scalar Arguments .. */
29 /* .. */
30 /* .. Array Arguments .. */
31 /* .. */
32
33 /* Purpose */
34 /* ======= */
35
36 /* CPBSV computes the solution to a complex system of linear equations */
37 /* A * X = B, */
38 /* where A is an N-by-N Hermitian positive definite band matrix and X */
39 /* and B are N-by-NRHS matrices. */
40
41 /* The Cholesky decomposition is used to factor A as */
42 /* A = U**H * U, if UPLO = 'U', or */
43 /* A = L * L**H, if UPLO = 'L', */
44 /* where U is an upper triangular band matrix, and L is a lower */
45 /* triangular band matrix, with the same number of superdiagonals or */
46 /* subdiagonals as A. The factored form of A is then used to solve the */
47 /* system of equations A * X = B. */
48
49 /* Arguments */
50 /* ========= */
51
52 /* UPLO (input) CHARACTER*1 */
53 /* = 'U': Upper triangle of A is stored; */
54 /* = 'L': Lower triangle of A is stored. */
55
56 /* N (input) INTEGER */
57 /* The number of linear equations, i.e., the order of the */
58 /* matrix A. N >= 0. */
59
60 /* KD (input) INTEGER */
61 /* The number of superdiagonals of the matrix A if UPLO = 'U', */
62 /* or the number of subdiagonals if UPLO = 'L'. KD >= 0. */
63
64 /* NRHS (input) INTEGER */
65 /* The number of right hand sides, i.e., the number of columns */
66 /* of the matrix B. NRHS >= 0. */
67
68 /* AB (input/output) COMPLEX array, dimension (LDAB,N) */
69 /* On entry, the upper or lower triangle of the Hermitian band */
70 /* matrix A, stored in the first KD+1 rows of the array. The */
71 /* j-th column of A is stored in the j-th column of the array AB */
72 /* as follows: */
73 /* if UPLO = 'U', AB(KD+1+i-j,j) = A(i,j) for max(1,j-KD)<=i<=j; */
74 /* if UPLO = 'L', AB(1+i-j,j) = A(i,j) for j<=i<=min(N,j+KD). */
75 /* See below for further details. */
76
77 /* On exit, if INFO = 0, the triangular factor U or L from the */
78 /* Cholesky factorization A = U**H*U or A = L*L**H of the band */
79 /* matrix A, in the same storage format as A. */
80
81 /* LDAB (input) INTEGER */
82 /* The leading dimension of the array AB. LDAB >= KD+1. */
83
84 /* B (input/output) COMPLEX array, dimension (LDB,NRHS) */
85 /* On entry, the N-by-NRHS right hand side matrix B. */
86 /* On exit, if INFO = 0, the N-by-NRHS solution matrix X. */
87
88 /* LDB (input) INTEGER */
89 /* The leading dimension of the array B. LDB >= max(1,N). */
90
91 /* INFO (output) INTEGER */
92 /* = 0: successful exit */
93 /* < 0: if INFO = -i, the i-th argument had an illegal value */
94 /* > 0: if INFO = i, the leading minor of order i of A is not */
95 /* positive definite, so the factorization could not be */
96 /* completed, and the solution has not been computed. */
97
98 /* Further Details */
99 /* =============== */
100
101 /* The band storage scheme is illustrated by the following example, when */
102 /* N = 6, KD = 2, and UPLO = 'U': */
103
104 /* On entry: On exit: */
105
106 /* * * a13 a24 a35 a46 * * u13 u24 u35 u46 */
107 /* * a12 a23 a34 a45 a56 * u12 u23 u34 u45 u56 */
108 /* a11 a22 a33 a44 a55 a66 u11 u22 u33 u44 u55 u66 */
109
110 /* Similarly, if UPLO = 'L' the format of A is as follows: */
111
112 /* On entry: On exit: */
113
114 /* a11 a22 a33 a44 a55 a66 l11 l22 l33 l44 l55 l66 */
115 /* a21 a32 a43 a54 a65 * l21 l32 l43 l54 l65 * */
116 /* a31 a42 a53 a64 * * l31 l42 l53 l64 * * */
117
118 /* Array elements marked * are not used by the routine. */
119
120 /* ===================================================================== */
121
122 /* .. External Functions .. */
123 /* .. */
124 /* .. External Subroutines .. */
125 /* .. */
126 /* .. Intrinsic Functions .. */
127 /* .. */
128 /* .. Executable Statements .. */
129
130 /* Test the input parameters. */
131
132 /* Parameter adjustments */
133 ab_dim1 = *ldab;
134 ab_offset = 1 + ab_dim1;
135 ab -= ab_offset;
136 b_dim1 = *ldb;
137 b_offset = 1 + b_dim1;
138 b -= b_offset;
139
140 /* Function Body */
141 *info = 0;
142 if (! lsame_(uplo, "U", (ftnlen)1, (ftnlen)1) && ! lsame_(uplo, "L", (
143 ftnlen)1, (ftnlen)1)) {
144 *info = -1;
145 } else if (*n < 0) {
146 *info = -2;
147 } else if (*kd < 0) {
148 *info = -3;
149 } else if (*nrhs < 0) {
150 *info = -4;
151 } else if (*ldab < *kd + 1) {
152 *info = -6;
153 } else if (*ldb < max(1,*n)) {
154 *info = -8;
155 }
156 if (*info != 0) {
157 i__1 = -(*info);
158 xerbla_("CPBSV ", &i__1, (ftnlen)6);
159 return 0;
160 }
161
162 /* Compute the Cholesky factorization A = U'*U or A = L*L'. */
163
164 cpbtrf_(uplo, n, kd, &ab[ab_offset], ldab, info, (ftnlen)1);
165 if (*info == 0) {
166
167 /* Solve the system A*X = B, overwriting B with X. */
168
169 cpbtrs_(uplo, n, kd, nrhs, &ab[ab_offset], ldab, &b[b_offset], ldb,
170 info, (ftnlen)1);
171
172 }
173 return 0;
174
175 /* End of CPBSV */
176
177 } /* cpbsv_ */
178
179