NAME

sgttrs - solve one of the systems of equations  A∗X = B or A’∗X = B,

SYNOPSIS

SUBROUTINE SGTTRS( TRANS, N, NRHS, DL, D, DU, DU2, IPIV, B, LDB, INFO )

CHARACTER TRANS

INTEGER INFO, LDB, N, NRHS

INTEGER IPIV( ∗ )

REAL B( LDB, ∗ ), D( ∗ ), DL( ∗ ), DU( ∗ ), DU2( ∗ )

#include <sunperf.h>

void sgttrs(char trans, int n, int nrhs, float ∗dl, float ∗d, float ∗du, float ∗du2, int ∗ipivot, float ∗sb, int ldb, int ∗info) ;

PURPOSE

SGTTRS solves one of the systems of equations
   A∗X = B  or  A’∗X = B, with a tridiagonal matrix A using the LU factorization computed by SGTTRF.
 

ARGUMENTS

TRANS (input) CHARACTER
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.

NRHS (input) INTEGER
The number of right hand sides, i.e., the number of columns of the matrix B.  NRHS >= 0.

DL (input) REAL array, dimension (N-1)
The (n-1) multipliers that define the matrix L from the LU factorization of A.

D (input) REAL array, dimension (N)
The n diagonal elements of the upper triangular matrix U from the LU factorization of A.

DU (input) REAL array, dimension (N-1)
The (n-1) elements of the first superdiagonal of U.

DU2 (input) REAL array, dimension (N-2)
The (n-2) elements of the second superdiagonal of U.

IPIV (input) INTEGER array, dimension (N)
The pivot indices; for 1 <= i <= n, row i of the matrix was interchanged with row IPIV(i).  IPIV(i) will always be either i or i+1; IPIV(i) = i indicates a row interchange was not required.

B (input/output) REAL array, dimension (LDB,NRHS)
On entry, the right hand side matrix B. On exit, B is overwritten by 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

SunOS 5.0  —  Last change: 10 Dec 1998