cgtsv-f(3)

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 (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 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 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 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 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 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

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