# cgtsv.f man page

cgtsv.f —

## Synopsis

### Functions/Subroutines

subroutinecgtsv(N, NRHS, DL, D, DU, B, LDB, INFO)CGTSV computes the solution to system of linear equations A * X = B for GT matrices

## Function/Subroutine Documentation

### subroutine cgtsv (integerN, integerNRHS, complex, dimension( * )DL, complex, dimension( * )D, complex, dimension( * )DU, complex, dimension( ldb, * )B, integerLDB, integerINFO)

**CGTSV computes the solution to system of linear equations A * X = B for GT matrices**

**Purpose:**

```
CGTSV solves the equation
A*X = B,
where A is an N-by-N tridiagonal matrix, by Gaussian elimination with
partial pivoting.
Note that the equation A**T *X = B may be solved by interchanging the
order of the arguments DU and DL.
```

**Parameters:**

*N*

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

*DL*

```
DL is COMPLEX array, dimension (N-1)
On entry, DL must contain the (n-1) subdiagonal elements of
A.
On exit, DL is overwritten by the (n-2) elements of the
second superdiagonal of the upper triangular matrix U from
the LU factorization of A, in DL(1), ..., DL(n-2).
```

*D*

```
D is COMPLEX array, dimension (N)
On entry, D must contain the diagonal elements of A.
On exit, D is overwritten by the n diagonal elements of U.
```

*DU*

```
DU is COMPLEX array, dimension (N-1)
On entry, DU must contain the (n-1) superdiagonal elements
of A.
On exit, DU is overwritten by the (n-1) elements of the first
superdiagonal of U.
```

*B*

```
B is COMPLEX array, dimension (LDB,NRHS)
On entry, the N-by-NRHS right hand side matrix B.
On exit, if INFO = 0, the N-by-NRHS solution matrix 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
> 0: if INFO = i, U(i,i) is exactly zero, and the solution
has not been computed. The factorization has not been
completed unless i = N.
```

**Author:**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**

September 2012

Definition at line 125 of file cgtsv.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

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

Sat Nov 16 2013 Version 3.4.2 LAPACK