#include "blaswrap.h"
#include "f2c.h"
/* Subroutine */ int cgtsv_(integer *n, integer *nrhs, complex *dl, complex *
d__, complex *du, complex *b, integer *ldb, integer *info)
{
/* -- LAPACK routine (version 3.1) --
Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
November 2006
Purpose
=======
CGTSV solves the equation
A*X = B,
where A is an N-by-N tridiagonal matrix, by Gaussian elimination with
partial pivoting.
Note that the equation A'*X = B may be solved by interchanging the
order of the arguments DU and DL.
Arguments
=========
N (input) INTEGER
The order of the matrix A. N >= 0.
NRHS (input) INTEGER
The number of right hand sides, i.e., the number of columns
of the matrix B. NRHS >= 0.
DL (input/output) COMPLEX array, dimension (N-1)
On entry, DL must contain the (n-1) subdiagonal elements of
A.
On exit, DL is overwritten by the (n-2) elements of the
second superdiagonal of the upper triangular matrix U from
the LU factorization of A, in DL(1), ..., DL(n-2).
D (input/output) COMPLEX array, dimension (N)
On entry, D must contain the diagonal elements of A.
On exit, D is overwritten by the n diagonal elements of U.
DU (input/output) COMPLEX array, dimension (N-1)
On entry, DU must contain the (n-1) superdiagonal elements
of A.
On exit, DU is overwritten by the (n-1) elements of the first
superdiagonal of U.
B (input/output) COMPLEX array, dimension (LDB,NRHS)
On entry, the N-by-NRHS right hand side matrix B.
On exit, if INFO = 0, the N-by-NRHS 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
> 0: if INFO = i, U(i,i) is exactly zero, and the solution
has not been computed. The factorization has not been
completed unless i = N.
=====================================================================
Parameter adjustments */
/* System generated locals */
integer b_dim1, b_offset, i__1, i__2, i__3, i__4, i__5, i__6, i__7;
real r__1, r__2, r__3, r__4;
complex q__1, q__2, q__3, q__4, q__5;
/* Builtin functions */
double r_imag(complex *);
void c_div(complex *, complex *, complex *);
/* Local variables */
static integer j, k;
static complex temp, mult;
extern /* Subroutine */ int xerbla_(char *, integer *);
--dl;
--d__;
--du;
b_dim1 = *ldb;
b_offset = 1 + b_dim1;
b -= b_offset;
/* Function Body */
*info = 0;
if (*n < 0) {
*info = -1;
} else if (*nrhs < 0) {
*info = -2;
} else if (*ldb < max(1,*n)) {
*info = -7;
}
if (*info != 0) {
i__1 = -(*info);
xerbla_("CGTSV ", &i__1);
return 0;
}
if (*n == 0) {
return 0;
}
i__1 = *n - 1;
for (k = 1; k <= i__1; ++k) {
i__2 = k;
if (dl[i__2].r == 0.f && dl[i__2].i == 0.f) {
/* Subdiagonal is zero, no elimination is required. */
i__2 = k;
if (d__[i__2].r == 0.f && d__[i__2].i == 0.f) {
/* Diagonal is zero: set INFO = K and return; a unique
solution can not be found. */
*info = k;
return 0;
}
} else /* if(complicated condition) */ {
i__2 = k;
i__3 = k;
if ((r__1 = d__[i__2].r, dabs(r__1)) + (r__2 = r_imag(&d__[k]),
dabs(r__2)) >= (r__3 = dl[i__3].r, dabs(r__3)) + (r__4 =
r_imag(&dl[k]), dabs(r__4))) {
/* No row interchange required */
c_div(&q__1, &dl[k], &d__[k]);
mult.r = q__1.r, mult.i = q__1.i;
i__2 = k + 1;
i__3 = k + 1;
i__4 = k;
q__2.r = mult.r * du[i__4].r - mult.i * du[i__4].i, q__2.i =
mult.r * du[i__4].i + mult.i * du[i__4].r;
q__1.r = d__[i__3].r - q__2.r, q__1.i = d__[i__3].i - q__2.i;
d__[i__2].r = q__1.r, d__[i__2].i = q__1.i;
i__2 = *nrhs;
for (j = 1; j <= i__2; ++j) {
i__3 = k + 1 + j * b_dim1;
i__4 = k + 1 + j * b_dim1;
i__5 = k + j * b_dim1;
q__2.r = mult.r * b[i__5].r - mult.i * b[i__5].i, q__2.i =
mult.r * b[i__5].i + mult.i * b[i__5].r;
q__1.r = b[i__4].r - q__2.r, q__1.i = b[i__4].i - q__2.i;
b[i__3].r = q__1.r, b[i__3].i = q__1.i;
/* L10: */
}
if (k < *n - 1) {
i__2 = k;
dl[i__2].r = 0.f, dl[i__2].i = 0.f;
}
} else {
/* Interchange rows K and K+1 */
c_div(&q__1, &d__[k], &dl[k]);
mult.r = q__1.r, mult.i = q__1.i;
i__2 = k;
i__3 = k;
d__[i__2].r = dl[i__3].r, d__[i__2].i = dl[i__3].i;
i__2 = k + 1;
temp.r = d__[i__2].r, temp.i = d__[i__2].i;
i__2 = k + 1;
i__3 = k;
q__2.r = mult.r * temp.r - mult.i * temp.i, q__2.i = mult.r *
temp.i + mult.i * temp.r;
q__1.r = du[i__3].r - q__2.r, q__1.i = du[i__3].i - q__2.i;
d__[i__2].r = q__1.r, d__[i__2].i = q__1.i;
if (k < *n - 1) {
i__2 = k;
i__3 = k + 1;
dl[i__2].r = du[i__3].r, dl[i__2].i = du[i__3].i;
i__2 = k + 1;
q__2.r = -mult.r, q__2.i = -mult.i;
i__3 = k;
q__1.r = q__2.r * dl[i__3].r - q__2.i * dl[i__3].i,
q__1.i = q__2.r * dl[i__3].i + q__2.i * dl[i__3]
.r;
du[i__2].r = q__1.r, du[i__2].i = q__1.i;
}
i__2 = k;
du[i__2].r = temp.r, du[i__2].i = temp.i;
i__2 = *nrhs;
for (j = 1; j <= i__2; ++j) {
i__3 = k + j * b_dim1;
temp.r = b[i__3].r, temp.i = b[i__3].i;
i__3 = k + j * b_dim1;
i__4 = k + 1 + j * b_dim1;
b[i__3].r = b[i__4].r, b[i__3].i = b[i__4].i;
i__3 = k + 1 + j * b_dim1;
i__4 = k + 1 + j * b_dim1;
q__2.r = mult.r * b[i__4].r - mult.i * b[i__4].i, q__2.i =
mult.r * b[i__4].i + mult.i * b[i__4].r;
q__1.r = temp.r - q__2.r, q__1.i = temp.i - q__2.i;
b[i__3].r = q__1.r, b[i__3].i = q__1.i;
/* L20: */
}
}
}
/* L30: */
}
i__1 = *n;
if (d__[i__1].r == 0.f && d__[i__1].i == 0.f) {
*info = *n;
return 0;
}
/* Back solve with the matrix U from the factorization. */
i__1 = *nrhs;
for (j = 1; j <= i__1; ++j) {
i__2 = *n + j * b_dim1;
c_div(&q__1, &b[*n + j * b_dim1], &d__[*n]);
b[i__2].r = q__1.r, b[i__2].i = q__1.i;
if (*n > 1) {
i__2 = *n - 1 + j * b_dim1;
i__3 = *n - 1 + j * b_dim1;
i__4 = *n - 1;
i__5 = *n + j * b_dim1;
q__3.r = du[i__4].r * b[i__5].r - du[i__4].i * b[i__5].i, q__3.i =
du[i__4].r * b[i__5].i + du[i__4].i * b[i__5].r;
q__2.r = b[i__3].r - q__3.r, q__2.i = b[i__3].i - q__3.i;
c_div(&q__1, &q__2, &d__[*n - 1]);
b[i__2].r = q__1.r, b[i__2].i = q__1.i;
}
for (k = *n - 2; k >= 1; --k) {
i__2 = k + j * b_dim1;
i__3 = k + j * b_dim1;
i__4 = k;
i__5 = k + 1 + j * b_dim1;
q__4.r = du[i__4].r * b[i__5].r - du[i__4].i * b[i__5].i, q__4.i =
du[i__4].r * b[i__5].i + du[i__4].i * b[i__5].r;
q__3.r = b[i__3].r - q__4.r, q__3.i = b[i__3].i - q__4.i;
i__6 = k;
i__7 = k + 2 + j * b_dim1;
q__5.r = dl[i__6].r * b[i__7].r - dl[i__6].i * b[i__7].i, q__5.i =
dl[i__6].r * b[i__7].i + dl[i__6].i * b[i__7].r;
q__2.r = q__3.r - q__5.r, q__2.i = q__3.i - q__5.i;
c_div(&q__1, &q__2, &d__[k]);
b[i__2].r = q__1.r, b[i__2].i = q__1.i;
/* L40: */
}
/* L50: */
}
return 0;
/* End of CGTSV */
} /* cgtsv_ */