.TH ZPTTRS 1 "November 2006" " LAPACK routine (version 3.1) " " LAPACK routine (version 3.1) " .SH NAME ZPTTRS - a tridiagonal system of the form A * X = B using the factorization A = U\(aq*D*U or A = L*D*L\(aq computed by ZPTTRF .SH SYNOPSIS .TP 19 SUBROUTINE ZPTTRS( UPLO, N, NRHS, D, E, B, LDB, INFO ) .TP 19 .ti +4 CHARACTER UPLO .TP 19 .ti +4 INTEGER INFO, LDB, N, NRHS .TP 19 .ti +4 DOUBLE PRECISION D( * ) .TP 19 .ti +4 COMPLEX*16 B( LDB, * ), E( * ) .SH PURPOSE ZPTTRS solves a tridiagonal system of the form A * X = B using the factorization A = U\(aq*D*U or A = L*D*L\(aq computed by ZPTTRF. 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. .br .SH ARGUMENTS .TP 8 UPLO (input) CHARACTER*1 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. = \(aqU\(aq: A = U\(aq*D*U, E is the superdiagonal of U .br = \(aqL\(aq: A = L*D*L\(aq, E is the subdiagonal of L .TP 8 N (input) INTEGER The order of the tridiagonal matrix A. N >= 0. .TP 8 NRHS (input) INTEGER The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0. .TP 8 D (input) DOUBLE PRECISION array, dimension (N) The n diagonal elements of the diagonal matrix D from the factorization A = U\(aq*D*U or A = L*D*L\(aq. .TP 8 E (input) COMPLEX*16 array, dimension (N-1) If UPLO = \(aqU\(aq, the (n-1) superdiagonal elements of the unit bidiagonal factor U from the factorization A = U\(aq*D*U. If UPLO = \(aqL\(aq, the (n-1) subdiagonal elements of the unit bidiagonal factor L from the factorization A = L*D*L\(aq. .TP 8 B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS) On entry, the right hand side vectors B for the system of linear equations. On exit, the solution vectors, X. .TP 8 LDB (input) INTEGER The leading dimension of the array B. LDB >= max(1,N). .TP 8 INFO (output) INTEGER = 0: successful exit .br < 0: if INFO = -k, the k-th argument had an illegal value