SYNOPSIS
 SUBROUTINE ZGTSV(
 N, NRHS, DL, D, DU, B, LDB, INFO )
 INTEGER INFO, LDB, N, NRHS
 COMPLEX*16 B( LDB, * ), D( * ), DL( * ), DU( * )
PURPOSE
ZGTSV solves the equation where A is an NbyN 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) COMPLEX*16 array, dimension (N1)
 On entry, DL must contain the (n1) subdiagonal elements of A. On exit, DL is overwritten by the (n2) elements of the second superdiagonal of the upper triangular matrix U from the LU factorization of A, in DL(1), ..., DL(n2).
 D (input/output) COMPLEX*16 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) COMPLEX*16 array, dimension (N1)
 On entry, DU must contain the (n1) superdiagonal elements of A. On exit, DU is overwritten by the (n1) elements of the first superdiagonal of U.
 B (input/output) COMPLEX*16 array, dimension (LDB,NRHS)
 On entry, the NbyNRHS right hand side matrix B. On exit, if INFO = 0, the NbyNRHS 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 ith 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.