NAME

zpttrs - solve a system of linear equations A ∗ X = B with a Hermitian positive definite tridiagonal matrix A using the factorization A = U∗∗H∗D∗U or A = L∗D∗L∗∗H computed by ZPTTRF

SYNOPSIS

SUBROUTINE ZPTTRS( UPLO, N, NRHS, D, E, B, LDB, INFO )

CHARACTER UPLO

INTEGER INFO, LDB, N, NRHS

DOUBLE PRECISION D( ∗ )

COMPLEX∗16 B( LDB, ∗ ), E( ∗ )

#include <sunperf.h>

void zpttrs(char uplo, int n, int nrhs, double ∗d, doublecomplex ∗e, doublecomplex ∗zb, int ldb, int ∗info) ;

PURPOSE

ZPTTRS solves a system of linear equations A ∗ X = B with a Hermitian positive definite tridiagonal matrix A using the factorization A = U∗∗H∗D∗U or A = L∗D∗L∗∗H computed by ZPTTRF. 
 

ARGUMENTS

UPLO (input) CHARACTER∗1
Specifies whether the superdiagonal or the subdiagonal of the tridiagonal matrix A is stored and the form of the factorization:
= ’U’:  E is the superdiagonal of U, and A = U’∗D∗U;
= ’L’:  E is the subdiagonal of L, and A = L∗D∗L’. (The two forms are equivalent if A is real.)

N (input) INTEGER
The order of the tridiagonal 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) DOUBLE PRECISION array, dimension (N)
The n diagonal elements of the diagonal matrix D from the factorization computed by ZPTTRF.

E (input) COMPLEX∗16 array, dimension (N-1)
The (n-1) off-diagonal elements of the unit bidiagonal factor U or L from the factorization computed by ZPTTRF (see UPLO).

B (input/output) DOUBLE PRECISION 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

SunOS 5.0  —  Last change: 10 Dec 1998