?dttrsb

Syntax

FORTRAN 77:

call sdttrsb( trans, n, nrhs, dl, d, du, b, ldb, info )

call ddttrsb( trans, n, nrhs, dl, d, du, b, ldb, info )

call cdttrsb( trans, n, nrhs, dl, d, du, b, ldb, info )

call zdttrsb( trans, n, nrhs, dl, d, du, b, ldb, info )

Include Files

The FORTRAN 77 interfaces are specified in the mkl_lapack.fi and mkl_lapack.h include files (to be used in Fortran programs) and in the mkl_lapack.h include file (to be used in C programs).

Description

The ?dttrsb routine solves the following systems of linear equations with multiple right hand sides for X:

A*X = B

if trans='N',

A^T*X = B

if trans='T',

A^H*X = B

if trans='C' (for complex matrices only).

Before calling this routine, call ?dttrfb to compute the factorization of A.

Input Parameters

trans

CHARACTER*1. Must be 'N' or 'T' or 'C'.

Indicates the form of the equations solved for X:

If trans = 'N', then A*X = B.

If trans = 'T', then A^T*X = B.

If trans = 'C', then A^H*X = B.

n

INTEGER. The order of A; n ≥ 0.

nrhs

INTEGER. The number of right-hand sides, that is, the number of columns in B; nrhs ≥ 0.

dl, d, du, b

REAL for sdttrsb

DOUBLE PRECISION for ddttrsb

COMPLEX for cdttrsb

DOUBLE COMPLEX for zdttrsb.

Arrays: dl(n -1), d(n), du(n -1), b(ldb,nrhs).

The array dl contains the (n - 1) multipliers that define the matrices L₁, L₂ from the factorization of A.

The array d contains the n diagonal elements of the upper triangular matrix U from the factorization of A.

The array du contains the (n - 1) elements of the superdiagonal of U.

The array b contains the matrix B whose columns are the right-hand sides for the systems of equations.

ldb

INTEGER. The leading dimension of b; ldb ≥ max(1, n).

Output Parameters

b

Overwritten by the solution matrix X.

info

INTEGER. If info = 0, the execution is successful.

If info = -i, the i-th parameter had an illegal value.