dgtsv man page on Scientific

```DGTSV(1)		 LAPACK routine (version 3.2)		      DGTSV(1)

NAME
DGTSV - solves the equation   A*X = B,

SYNOPSIS
SUBROUTINE DGTSV( N, NRHS, DL, D, DU, B, LDB, INFO )

INTEGER	 INFO, LDB, N, NRHS

DOUBLE	 PRECISION B( LDB, * ), D( * ), DL( * ), DU( * )

PURPOSE
DGTSV   solves the equation where A is an n by n tridiagonal matrix, by
Gaussian elimination with partial pivoting.
Note that the equation  A'*X = B	 may be solved	by  interchanging  the
order of the arguments DU and DL.

ARGUMENTS
N       (input) INTEGER
The order of the 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.

DL      (input/output) DOUBLE PRECISION array, dimension (N-1)
On entry, DL must contain the (n-1) sub-diagonal elements of A.
On  exit, DL is overwritten by the (n-2) elements of the second
super-diagonal of the upper triangular matrix  U	 from  the  LU
factorization of A, in DL(1), ..., DL(n-2).

D       (input/output) DOUBLE PRECISION 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      (input/output) DOUBLE PRECISION array, dimension (N-1)
On entry, DU must contain the (n-1) super-diagonal elements  of
A.   On	exit,  DU  is overwritten by the (n-1) elements of the
first super-diagonal of U.

B       (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
On entry, the N by NRHS matrix of right hand side matrix B.  On
exit, if INFO = 0, the N by NRHS solution matrix X.

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

INFO    (output) 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.

LAPACK routine (version 3.2)	 November 2008			      DGTSV(1)
```
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