# dgttrs.f man page

dgttrs.f —

## Synopsis

### Functions/Subroutines

subroutinedgttrs(TRANS, N, NRHS, DL, D, DU, DU2, IPIV, B, LDB, INFO)DGTTRS

## Function/Subroutine Documentation

### subroutine dgttrs (characterTRANS, integerN, integerNRHS, double precision, dimension( * )DL, double precision, dimension( * )D, double precision, dimension( * )DU, double precision, dimension( * )DU2, integer, dimension( * )IPIV, double precision, dimension( ldb, * )B, integerLDB, integerINFO)

**DGTTRS**

**Purpose:**

```
DGTTRS solves one of the systems of equations
A*X = B or A**T*X = B,
with a tridiagonal matrix A using the LU factorization computed
by DGTTRF.
```

**Parameters:**

*TRANS*

```
TRANS is CHARACTER*1
Specifies the form of the system of equations.
= 'N': A * X = B (No transpose)
= 'T': A**T* X = B (Transpose)
= 'C': A**T* X = B (Conjugate transpose = Transpose)
```

*N*

```
N is INTEGER
The order of the matrix A.
```

*NRHS*

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

*DL*

```
DL is DOUBLE PRECISION array, dimension (N-1)
The (n-1) multipliers that define the matrix L from the
LU factorization of A.
```

*D*

```
D is DOUBLE PRECISION array, dimension (N)
The n diagonal elements of the upper triangular matrix U from
the LU factorization of A.
```

*DU*

```
DU is DOUBLE PRECISION array, dimension (N-1)
The (n-1) elements of the first super-diagonal of U.
```

*DU2*

```
DU2 is DOUBLE PRECISION array, dimension (N-2)
The (n-2) elements of the second super-diagonal of U.
```

*IPIV*

```
IPIV is INTEGER array, dimension (N)
The pivot indices; for 1 <= i <= n, row i of the matrix was
interchanged with row IPIV(i). IPIV(i) will always be either
i or i+1; IPIV(i) = i indicates a row interchange was not
required.
```

*B*

```
B is DOUBLE PRECISION array, dimension (LDB,NRHS)
On entry, the matrix of right hand side vectors B.
On exit, B is overwritten by 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 = -i, the i-th argument had an illegal value
```

**Author:**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**

September 2012

Definition at line 138 of file dgttrs.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

dgttrs(3) is an alias of dgttrs.f(3).