NAME

cpttrs - 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 CPTTRF

SYNOPSIS

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

void cpttrs(char uplo, long int n, long int nrhs, float ∗d,
complex ∗e, complex ∗cb, long int ldb, long int ∗info)

CHARACTER UPLO

INTEGER INFO, LDB, N, NRHS

REAL D( ∗ )

COMPLEX B( LDB, ∗ ), E( ∗ )

PURPOSE

CPTTRS 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 CPTTRF. 
 

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) REAL array, dimension (N)
The n diagonal elements of the diagonal matrix D from the factorization computed by CPTTRF.

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

B       (input/output) REAL 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

Sun, Inc.  —  Last change: 20 Sep 1996