cptts2 (l) - Linux Manuals

cptts2: solves a tridiagonal system of the form A * X = B using the factorization A = Uaq*D*U or A = L*D*Laq computed by CPTTRF

NAME

CPTTS2 - solves a tridiagonal system of the form A * X = B using the factorization A = Uaq*D*U or A = L*D*Laq computed by CPTTRF

SYNOPSIS

SUBROUTINE CPTTS2(

IUPLO, N, NRHS, D, E, B, LDB )

    

INTEGER IUPLO, LDB, N, NRHS

    

REAL D( * )

    

COMPLEX B( LDB, * ), E( * )

PURPOSE

CPTTS2 solves a tridiagonal system of the form
A * X = B using the factorization A = Uaq*D*U or A = L*D*Laq computed by CPTTRF. D is a diagonal matrix specified in the vector D, U (or L) is a unit bidiagonal matrix whose superdiagonal (subdiagonal) is specified in the vector E, and X and B are N by NRHS matrices.

ARGUMENTS

IUPLO (input) INTEGER

Specifies the form of the factorization and whether the vector E is the superdiagonal of the upper bidiagonal factor U or the subdiagonal of the lower bidiagonal factor L. = 1: A = Uaq*D*U, E is the superdiagonal of U
= 0: A = L*D*Laq, E is the subdiagonal of L

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 A = Uaq*D*U or A = L*D*Laq.

E (input) COMPLEX array, dimension (N-1)

If IUPLO = 1, the (n-1) superdiagonal elements of the unit bidiagonal factor U from the factorization A = Uaq*D*U. If IUPLO = 0, the (n-1) subdiagonal elements of the unit bidiagonal factor L from the factorization A = L*D*Laq.

B (input/output) REAL array, dimension (LDB,NRHS)

On entry, the right hand side vectors B for the system of linear equations. On exit, the solution vectors, X.

LDB (input) INTEGER

The leading dimension of the array B. LDB >= max(1,N).