.TH SPTTRS 1 "November 2006" " LAPACK routine (version 3.1) " " LAPACK routine (version 3.1) " .SH NAME SPTTRS - a tridiagonal system of the form A * X = B using the L*D*L\(aq factorization of A computed by SPTTRF .SH SYNOPSIS .TP 19 SUBROUTINE SPTTRS( N, NRHS, D, E, B, LDB, INFO ) .TP 19 .ti +4 INTEGER INFO, LDB, N, NRHS .TP 19 .ti +4 REAL B( LDB, * ), D( * ), E( * ) .SH PURPOSE SPTTRS solves a tridiagonal system of the form A * X = B using the L*D*L\(aq factorization of A computed by SPTTRF. D is a diagonal matrix specified in the vector D, L is a unit bidiagonal matrix whose subdiagonal is specified in the vector E, and X and B are N by NRHS matrices. .br .SH ARGUMENTS .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) REAL array, dimension (N) The n diagonal elements of the diagonal matrix D from the L*D*L\(aq factorization of A. .TP 8 E (input) REAL array, dimension (N-1) The (n-1) subdiagonal elements of the unit bidiagonal factor L from the L*D*L\(aq factorization of A. E can also be regarded as the superdiagonal of the unit bidiagonal factor U from the factorization A = U\(aq*D*U. .TP 8 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. .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