# cgtsv.f - Man Page

SRC/cgtsv.f

## Synopsis

### Functions/Subroutines

subroutine **cgtsv** (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 (integer n, integer nrhs, complex, dimension( * ) dl, complex, dimension( * ) d, complex, dimension( * ) du, complex, dimension( ldb, * ) b, integer ldb, integer info)

**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.

Definition at line **123** of file **cgtsv.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

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

Tue Nov 28 2023 12:08:41 Version 3.12.0 LAPACK