Contents
cgtsv - solve the equation A*X = B,
SUBROUTINE CGTSV(N, NRHS, LOW, D, UP, B, LDB, INFO)
COMPLEX LOW(*), D(*), UP(*), B(LDB,*)
INTEGER N, NRHS, LDB, INFO
SUBROUTINE CGTSV_64(N, NRHS, LOW, D, UP, B, LDB, INFO)
COMPLEX LOW(*), D(*), UP(*), B(LDB,*)
INTEGER*8 N, NRHS, LDB, INFO
F95 INTERFACE
SUBROUTINE GTSV([N], [NRHS], LOW, D, UP, B, [LDB], [INFO])
COMPLEX, DIMENSION(:) :: LOW, D, UP
COMPLEX, DIMENSION(:,:) :: B
INTEGER :: N, NRHS, LDB, INFO
SUBROUTINE GTSV_64([N], [NRHS], LOW, D, UP, B, [LDB], [INFO])
COMPLEX, DIMENSION(:) :: LOW, D, UP
COMPLEX, DIMENSION(:,:) :: B
INTEGER(8) :: N, NRHS, LDB, INFO
C INTERFACE
#include <sunperf.h>
void cgtsv(int n, int nrhs, complex *low, complex *diag,
complex *up, complex *b, int ldb, int *info);
void cgtsv_64(long n, long nrhs, complex *low, complex
*diag, complex *up, complex *b, long ldb, long
*info);
cgtsv solves the equation
where A is an N-by-N tridiagonal matrix, by Gaussian elimi-
nation with partial pivoting.
Note that the equation A'*X = B may be solved by inter-
changing the order of the arguments DU and DL.
N (input) The order of the matrix A. N >= 0.
NRHS (input)
The number of right hand sides, i.e., the number
of columns of the matrix B. NRHS >= 0.
LOW (input/output)
On entry, LOW must contain the (n-1) subdiagonal
elements of A. On exit, LOW is overwritten by the
(n-2) elements of the second superdiagonal of the
upper triangular matrix U from the LU factoriza-
tion of A, in LOW(1), ..., LOW(n-2).
D (input/output)
On entry, D must contain the diagonal elements of
A. On exit, D is overwritten by the n diagonal
elements of U.
UP (input/output)
On entry, UP must contain the (n-1) superdiagonal
elements of A. On exit, UP is overwritten by the
(n-1) elements of the first superdiagonal of U.
B (input/output)
On entry, the N-by-NRHS right hand side matrix B.
On exit, if INFO = 0, the N-by-NRHS solution
matrix X.
LDB (input)
The leading dimension of the array B. LDB >=
max(1,N).
INFO (output)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille-
gal 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.