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/* sgbtrs.f -- translated by f2c (version 20061008).
You must link the resulting object file with libf2c:
on Microsoft Windows system, link with libf2c.lib;
on Linux or Unix systems, link with .../path/to/libf2c.a -lm
or, if you install libf2c.a in a standard place, with -lf2c -lm
-- in that order, at the end of the command line, as in
cc *.o -lf2c -lm
Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
http://www.netlib.org/f2c/libf2c.zip
*/
#include "f2c.h"
#include "blaswrap.h"
/* Table of constant values */
static real c_b7 = -1.f;
static integer c__1 = 1;
static real c_b23 = 1.f;
/* Subroutine */ int sgbtrs_(char *trans, integer *n, integer *kl, integer *
ku, integer *nrhs, real *ab, integer *ldab, integer *ipiv, real *b,
integer *ldb, integer *info)
{
/* System generated locals */
integer ab_dim1, ab_offset, b_dim1, b_offset, i__1, i__2, i__3;
/* Local variables */
integer i__, j, l, kd, lm;
extern /* Subroutine */ int sger_(integer *, integer *, real *, real *,
integer *, real *, integer *, real *, integer *);
extern logical lsame_(char *, char *);
extern /* Subroutine */ int sgemv_(char *, integer *, integer *, real *,
real *, integer *, real *, integer *, real *, real *, integer *);
logical lnoti;
extern /* Subroutine */ int sswap_(integer *, real *, integer *, real *,
integer *), stbsv_(char *, char *, char *, integer *, integer *,
real *, integer *, real *, integer *),
xerbla_(char *, integer *);
logical notran;
/* -- LAPACK routine (version 3.2) -- */
/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/* November 2006 */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* SGBTRS solves a system of linear equations */
/* A * X = B or A' * X = B */
/* with a general band matrix A using the LU factorization computed */
/* by SGBTRF. */
/* Arguments */
/* ========= */
/* TRANS (input) CHARACTER*1 */
/* Specifies the form of the system of equations. */
/* = 'N': A * X = B (No transpose) */
/* = 'T': A'* X = B (Transpose) */
/* = 'C': A'* X = B (Conjugate transpose = Transpose) */
/* N (input) INTEGER */
/* The order of the matrix A. N >= 0. */
/* KL (input) INTEGER */
/* The number of subdiagonals within the band of A. KL >= 0. */
/* KU (input) INTEGER */
/* The number of superdiagonals within the band of A. KU >= 0. */
/* NRHS (input) INTEGER */
/* The number of right hand sides, i.e., the number of columns */
/* of the matrix B. NRHS >= 0. */
/* AB (input) REAL array, dimension (LDAB,N) */
/* Details of the LU factorization of the band matrix A, as */
/* computed by SGBTRF. U is stored as an upper triangular band */
/* matrix with KL+KU superdiagonals in rows 1 to KL+KU+1, and */
/* the multipliers used during the factorization are stored in */
/* rows KL+KU+2 to 2*KL+KU+1. */
/* LDAB (input) INTEGER */
/* The leading dimension of the array AB. LDAB >= 2*KL+KU+1. */
/* IPIV (input) INTEGER array, dimension (N) */
/* The pivot indices; for 1 <= i <= N, row i of the matrix was */
/* interchanged with row IPIV(i). */
/* B (input/output) REAL array, dimension (LDB,NRHS) */
/* On entry, the right hand side matrix B. */
/* On exit, the solution matrix X. */
/* LDB (input) INTEGER */
/* The leading dimension of the array B. LDB >= max(1,N). */
/* INFO (output) INTEGER */
/* = 0: successful exit */
/* < 0: if INFO = -i, the i-th argument had an illegal value */
/* ===================================================================== */
/* .. Parameters .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Test the input parameters. */
/* Parameter adjustments */
ab_dim1 = *ldab;
ab_offset = 1 + ab_dim1;
ab -= ab_offset;
--ipiv;
b_dim1 = *ldb;
b_offset = 1 + b_dim1;
b -= b_offset;
/* Function Body */
*info = 0;
notran = lsame_(trans, "N");
if (! notran && ! lsame_(trans, "T") && ! lsame_(
trans, "C")) {
*info = -1;
} else if (*n < 0) {
*info = -2;
} else if (*kl < 0) {
*info = -3;
} else if (*ku < 0) {
*info = -4;
} else if (*nrhs < 0) {
*info = -5;
} else if (*ldab < (*kl << 1) + *ku + 1) {
*info = -7;
} else if (*ldb < max(1,*n)) {
*info = -10;
}
if (*info != 0) {
i__1 = -(*info);
xerbla_("SGBTRS", &i__1);
return 0;
}
/* Quick return if possible */
if (*n == 0 || *nrhs == 0) {
return 0;
}
kd = *ku + *kl + 1;
lnoti = *kl > 0;
if (notran) {
/* Solve A*X = B. */
/* Solve L*X = B, overwriting B with X. */
/* L is represented as a product of permutations and unit lower */
/* triangular matrices L = P(1) * L(1) * ... * P(n-1) * L(n-1), */
/* where each transformation L(i) is a rank-one modification of */
/* the identity matrix. */
if (lnoti) {
i__1 = *n - 1;
for (j = 1; j <= i__1; ++j) {
/* Computing MIN */
i__2 = *kl, i__3 = *n - j;
lm = min(i__2,i__3);
l = ipiv[j];
if (l != j) {
sswap_(nrhs, &b[l + b_dim1], ldb, &b[j + b_dim1], ldb);
}
sger_(&lm, nrhs, &c_b7, &ab[kd + 1 + j * ab_dim1], &c__1, &b[
j + b_dim1], ldb, &b[j + 1 + b_dim1], ldb);
/* L10: */
}
}
i__1 = *nrhs;
for (i__ = 1; i__ <= i__1; ++i__) {
/* Solve U*X = B, overwriting B with X. */
i__2 = *kl + *ku;
stbsv_("Upper", "No transpose", "Non-unit", n, &i__2, &ab[
ab_offset], ldab, &b[i__ * b_dim1 + 1], &c__1);
/* L20: */
}
} else {
/* Solve A'*X = B. */
i__1 = *nrhs;
for (i__ = 1; i__ <= i__1; ++i__) {
/* Solve U'*X = B, overwriting B with X. */
i__2 = *kl + *ku;
stbsv_("Upper", "Transpose", "Non-unit", n, &i__2, &ab[ab_offset],
ldab, &b[i__ * b_dim1 + 1], &c__1);
/* L30: */
}
/* Solve L'*X = B, overwriting B with X. */
if (lnoti) {
for (j = *n - 1; j >= 1; --j) {
/* Computing MIN */
i__1 = *kl, i__2 = *n - j;
lm = min(i__1,i__2);
sgemv_("Transpose", &lm, nrhs, &c_b7, &b[j + 1 + b_dim1], ldb,
&ab[kd + 1 + j * ab_dim1], &c__1, &c_b23, &b[j +
b_dim1], ldb);
l = ipiv[j];
if (l != j) {
sswap_(nrhs, &b[l + b_dim1], ldb, &b[j + b_dim1], ldb);
}
/* L40: */
}
}
}
return 0;
/* End of SGBTRS */
} /* sgbtrs_ */
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