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/* dlagtm.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"
/* Subroutine */ int dlagtm_(char *trans, integer *n, integer *nrhs,
doublereal *alpha, doublereal *dl, doublereal *d__, doublereal *du,
doublereal *x, integer *ldx, doublereal *beta, doublereal *b, integer
*ldb)
{
/* System generated locals */
integer b_dim1, b_offset, x_dim1, x_offset, i__1, i__2;
/* Local variables */
integer i__, j;
extern logical lsame_(char *, char *);
/* -- LAPACK auxiliary routine (version 3.2) -- */
/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/* November 2006 */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* DLAGTM performs a matrix-vector product of the form */
/* B := alpha * A * X + beta * B */
/* where A is a tridiagonal matrix of order N, B and X are N by NRHS */
/* matrices, and alpha and beta are real scalars, each of which may be */
/* 0., 1., or -1. */
/* Arguments */
/* ========= */
/* TRANS (input) CHARACTER*1 */
/* Specifies the operation applied to A. */
/* = 'N': No transpose, B := alpha * A * X + beta * B */
/* = 'T': Transpose, B := alpha * A'* X + beta * B */
/* = 'C': Conjugate transpose = Transpose */
/* 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 matrices X and B. */
/* ALPHA (input) DOUBLE PRECISION */
/* The scalar alpha. ALPHA must be 0., 1., or -1.; otherwise, */
/* it is assumed to be 0. */
/* DL (input) DOUBLE PRECISION array, dimension (N-1) */
/* The (n-1) sub-diagonal elements of T. */
/* D (input) DOUBLE PRECISION array, dimension (N) */
/* The diagonal elements of T. */
/* DU (input) DOUBLE PRECISION array, dimension (N-1) */
/* The (n-1) super-diagonal elements of T. */
/* X (input) DOUBLE PRECISION array, dimension (LDX,NRHS) */
/* The N by NRHS matrix X. */
/* LDX (input) INTEGER */
/* The leading dimension of the array X. LDX >= max(N,1). */
/* BETA (input) DOUBLE PRECISION */
/* The scalar beta. BETA must be 0., 1., or -1.; otherwise, */
/* it is assumed to be 1. */
/* B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS) */
/* On entry, the N by NRHS matrix B. */
/* On exit, B is overwritten by the matrix expression */
/* B := alpha * A * X + beta * B. */
/* LDB (input) INTEGER */
/* The leading dimension of the array B. LDB >= max(N,1). */
/* ===================================================================== */
/* .. Parameters .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Parameter adjustments */
--dl;
--d__;
--du;
x_dim1 = *ldx;
x_offset = 1 + x_dim1;
x -= x_offset;
b_dim1 = *ldb;
b_offset = 1 + b_dim1;
b -= b_offset;
/* Function Body */
if (*n == 0) {
return 0;
}
/* Multiply B by BETA if BETA.NE.1. */
if (*beta == 0.) {
i__1 = *nrhs;
for (j = 1; j <= i__1; ++j) {
i__2 = *n;
for (i__ = 1; i__ <= i__2; ++i__) {
b[i__ + j * b_dim1] = 0.;
/* L10: */
}
/* L20: */
}
} else if (*beta == -1.) {
i__1 = *nrhs;
for (j = 1; j <= i__1; ++j) {
i__2 = *n;
for (i__ = 1; i__ <= i__2; ++i__) {
b[i__ + j * b_dim1] = -b[i__ + j * b_dim1];
/* L30: */
}
/* L40: */
}
}
if (*alpha == 1.) {
if (lsame_(trans, "N")) {
/* Compute B := B + A*X */
i__1 = *nrhs;
for (j = 1; j <= i__1; ++j) {
if (*n == 1) {
b[j * b_dim1 + 1] += d__[1] * x[j * x_dim1 + 1];
} else {
b[j * b_dim1 + 1] = b[j * b_dim1 + 1] + d__[1] * x[j *
x_dim1 + 1] + du[1] * x[j * x_dim1 + 2];
b[*n + j * b_dim1] = b[*n + j * b_dim1] + dl[*n - 1] * x[*
n - 1 + j * x_dim1] + d__[*n] * x[*n + j * x_dim1]
;
i__2 = *n - 1;
for (i__ = 2; i__ <= i__2; ++i__) {
b[i__ + j * b_dim1] = b[i__ + j * b_dim1] + dl[i__ -
1] * x[i__ - 1 + j * x_dim1] + d__[i__] * x[
i__ + j * x_dim1] + du[i__] * x[i__ + 1 + j *
x_dim1];
/* L50: */
}
}
/* L60: */
}
} else {
/* Compute B := B + A'*X */
i__1 = *nrhs;
for (j = 1; j <= i__1; ++j) {
if (*n == 1) {
b[j * b_dim1 + 1] += d__[1] * x[j * x_dim1 + 1];
} else {
b[j * b_dim1 + 1] = b[j * b_dim1 + 1] + d__[1] * x[j *
x_dim1 + 1] + dl[1] * x[j * x_dim1 + 2];
b[*n + j * b_dim1] = b[*n + j * b_dim1] + du[*n - 1] * x[*
n - 1 + j * x_dim1] + d__[*n] * x[*n + j * x_dim1]
;
i__2 = *n - 1;
for (i__ = 2; i__ <= i__2; ++i__) {
b[i__ + j * b_dim1] = b[i__ + j * b_dim1] + du[i__ -
1] * x[i__ - 1 + j * x_dim1] + d__[i__] * x[
i__ + j * x_dim1] + dl[i__] * x[i__ + 1 + j *
x_dim1];
/* L70: */
}
}
/* L80: */
}
}
} else if (*alpha == -1.) {
if (lsame_(trans, "N")) {
/* Compute B := B - A*X */
i__1 = *nrhs;
for (j = 1; j <= i__1; ++j) {
if (*n == 1) {
b[j * b_dim1 + 1] -= d__[1] * x[j * x_dim1 + 1];
} else {
b[j * b_dim1 + 1] = b[j * b_dim1 + 1] - d__[1] * x[j *
x_dim1 + 1] - du[1] * x[j * x_dim1 + 2];
b[*n + j * b_dim1] = b[*n + j * b_dim1] - dl[*n - 1] * x[*
n - 1 + j * x_dim1] - d__[*n] * x[*n + j * x_dim1]
;
i__2 = *n - 1;
for (i__ = 2; i__ <= i__2; ++i__) {
b[i__ + j * b_dim1] = b[i__ + j * b_dim1] - dl[i__ -
1] * x[i__ - 1 + j * x_dim1] - d__[i__] * x[
i__ + j * x_dim1] - du[i__] * x[i__ + 1 + j *
x_dim1];
/* L90: */
}
}
/* L100: */
}
} else {
/* Compute B := B - A'*X */
i__1 = *nrhs;
for (j = 1; j <= i__1; ++j) {
if (*n == 1) {
b[j * b_dim1 + 1] -= d__[1] * x[j * x_dim1 + 1];
} else {
b[j * b_dim1 + 1] = b[j * b_dim1 + 1] - d__[1] * x[j *
x_dim1 + 1] - dl[1] * x[j * x_dim1 + 2];
b[*n + j * b_dim1] = b[*n + j * b_dim1] - du[*n - 1] * x[*
n - 1 + j * x_dim1] - d__[*n] * x[*n + j * x_dim1]
;
i__2 = *n - 1;
for (i__ = 2; i__ <= i__2; ++i__) {
b[i__ + j * b_dim1] = b[i__ + j * b_dim1] - du[i__ -
1] * x[i__ - 1 + j * x_dim1] - d__[i__] * x[
i__ + j * x_dim1] - dl[i__] * x[i__ + 1 + j *
x_dim1];
/* L110: */
}
}
/* L120: */
}
}
}
return 0;
/* End of DLAGTM */
} /* dlagtm_ */
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