cgtsv(3P) Sun Performance Library cgtsv(3P)NAMEcgtsv - solve the equation A*X = B,
SYNOPSIS
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 *d, complex *up, com‐
plex *b, int ldb, int *info);
void cgtsv_64(long n, long nrhs, complex *low, complex *d, complex *up,
complex *b, long ldb, long *info);
PURPOSEcgtsv solves the equation
where A is an N-by-N 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) 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 factorization 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 illegal value
> 0: if INFO = i, U(i,i) is exactly zero, and the solution
has not been computed. The factorization has not been com‐
pleted unless i = N.
6 Mar 2009 cgtsv(3P)
