# SPTTRS (3) - Linux Man Pages

spttrs.f -

## SYNOPSIS

### Functions/Subroutines

subroutine spttrs (N, NRHS, D, E, B, LDB, INFO)
SPTTRS

## Function/Subroutine Documentation

### subroutine spttrs (integerN, integerNRHS, real, dimension( * )D, real, dimension( * )E, real, dimension( ldb, * )B, integerLDB, integerINFO)

SPTTRS

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.
```

Parameters:

N

```          N is INTEGER
The order of the tridiagonal matrix A.  N >= 0.
```

NRHS

```          NRHS is INTEGER
The number of right hand sides, i.e., the number of columns
of the matrix B.  NRHS >= 0.
```

D

```          D is REAL array, dimension (N)
The n diagonal elements of the diagonal matrix D from the
L*D*L**T factorization of A.
```

E

```          E is 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

```          B is 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

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

INFO

```          INFO is INTEGER
= 0: successful exit
< 0: if INFO = -k, the k-th argument had an illegal value
```

Author:

Univ. of Tennessee

Univ. of California Berkeley