# sgtsv.f man page

sgtsv.f —

## Synopsis

### Functions/Subroutines

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

## Function/Subroutine Documentation

### subroutine sgtsv (integer N, integer NRHS, real, dimension( * ) DL, real, dimension( * ) D, real, dimension( * ) DU, real, dimension( ldb, * ) B, integer LDB, integer INFO)

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

**Purpose:**

SGTSV 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 REAL 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*D is REAL 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 REAL 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*B is REAL 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*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:**December 2016

Definition at line 129 of file sgtsv.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page sgtsv(3) is an alias of sgtsv.f(3).

Sat Jun 24 2017 Version 3.7.1 LAPACK