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/* sptsv.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 sptsv_(integer *n, integer *nrhs, real *d__, real *e,
real *b, integer *ldb, integer *info)
{
/* System generated locals */
integer b_dim1, b_offset, i__1;
/* Local variables */
extern /* Subroutine */ int xerbla_(char *, integer *), spttrf_(
integer *, real *, real *, integer *), spttrs_(integer *, integer
*, real *, real *, real *, integer *, integer *);
/* -- LAPACK routine (version 3.2) -- */
/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/* November 2006 */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* SPTSV computes the solution to a real system of linear equations */
/* A*X = B, where A is an N-by-N symmetric positive definite tridiagonal */
/* matrix, and X and B are N-by-NRHS matrices. */
/* A is factored as A = L*D*L**T, and the factored form of A is then */
/* used to solve the system of equations. */
/* 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. */
/* D (input/output) REAL array, dimension (N) */
/* On entry, the n diagonal elements of the tridiagonal matrix */
/* A. On exit, the n diagonal elements of the diagonal matrix */
/* D from the factorization A = L*D*L**T. */
/* E (input/output) REAL array, dimension (N-1) */
/* On entry, the (n-1) subdiagonal elements of the tridiagonal */
/* matrix A. On exit, the (n-1) subdiagonal elements of the */
/* unit bidiagonal factor L from the L*D*L**T factorization of */
/* A. (E can also be regarded as the superdiagonal of the unit */
/* bidiagonal factor U from the U**T*D*U factorization of A.) */
/* B (input/output) REAL 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, the leading minor of order i is not */
/* positive definite, and the solution has not been */
/* computed. The factorization has not been completed */
/* unless i = N. */
/* ===================================================================== */
/* .. External Subroutines .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Test the input parameters. */
/* Parameter adjustments */
--d__;
--e;
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 = -6;
}
if (*info != 0) {
i__1 = -(*info);
xerbla_("SPTSV ", &i__1);
return 0;
}
/* Compute the L*D*L' (or U'*D*U) factorization of A. */
spttrf_(n, &d__[1], &e[1], info);
if (*info == 0) {
/* Solve the system A*X = B, overwriting B with X. */
spttrs_(n, nrhs, &d__[1], &e[1], &b[b_offset], ldb, info);
}
return 0;
/* End of SPTSV */
} /* sptsv_ */
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