Provided by: liblapack-doc_3.3.1-1_all

**NAME**

LAPACK-3 - solves a tridiagonal system of the form A * X = B using the L*D*L**T factorization of A computed by SPTTRF

**SYNOPSIS**

SUBROUTINE SPTTRS( N, NRHS, D, E, B, LDB, INFO ) INTEGER INFO, LDB, N, NRHS REAL B( LDB, * ), D( * ), E( * )

**PURPOSE**

SPTTRS solves a tridiagonal system of the form A * X = B using the L*D*L**T 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.

**ARGUMENTS**

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 L*D*L**T factorization of A. E (input) REAL array, dimension (N-1) The (n-1) subdiagonal elements of the unit bidiagonal factor L from the L*D*L**T factorization of A. E can also be regarded as the superdiagonal of the unit bidiagonal factor U from the factorization A = U**T*D*U. 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). INFO (output) INTEGER = 0: successful exit < 0: if INFO = -k, the k-th argument had an illegal value LAPACK routine (version 3.3.1) April 2011 SPTTRS(3lapack)