dgttrs(3P) Sun Performance Library dgttrs(3P)NAMEdgttrs - solve one of the systems of equations A*X = B or A'*X = B,
SYNOPSIS
SUBROUTINE DGTTRS(TRANSA, N, NRHS, LOW, D, UP1, UP2, IPIVOT, B,
LDB, INFO)
CHARACTER * 1 TRANSA
INTEGER N, NRHS, LDB, INFO
INTEGER IPIVOT(*)
DOUBLE PRECISION LOW(*), D(*), UP1(*), UP2(*), B(LDB,*)
SUBROUTINE DGTTRS_64(TRANSA, N, NRHS, LOW, D, UP1, UP2, IPIVOT, B,
LDB, INFO)
CHARACTER * 1 TRANSA
INTEGER*8 N, NRHS, LDB, INFO
INTEGER*8 IPIVOT(*)
DOUBLE PRECISION LOW(*), D(*), UP1(*), UP2(*), B(LDB,*)
F95 INTERFACE
SUBROUTINE GTTRS([TRANSA], [N], [NRHS], LOW, D, UP1, UP2, IPIVOT,
B, [LDB], [INFO])
CHARACTER(LEN=1) :: TRANSA
INTEGER :: N, NRHS, LDB, INFO
INTEGER, DIMENSION(:) :: IPIVOT
REAL(8), DIMENSION(:) :: LOW, D, UP1, UP2
REAL(8), DIMENSION(:,:) :: B
SUBROUTINE GTTRS_64([TRANSA], [N], [NRHS], LOW, D, UP1, UP2,
IPIVOT, B, [LDB], [INFO])
CHARACTER(LEN=1) :: TRANSA
INTEGER(8) :: N, NRHS, LDB, INFO
INTEGER(8), DIMENSION(:) :: IPIVOT
REAL(8), DIMENSION(:) :: LOW, D, UP1, UP2
REAL(8), DIMENSION(:,:) :: B
C INTERFACE
#include <sunperf.h>
void dgttrs(char transa, int n, int nrhs, double *low, double *d, dou‐
ble *up1, double *up2, int *ipivot, double *b, int ldb, int
*info);
void dgttrs_64(char transa, long n, long nrhs, double *low, double *d,
double *up1, double *up2, long *ipivot, double *b, long ldb,
long *info);
PURPOSEdgttrs solves one of the systems of equations
A*X = B or A'*X = B, with a tridiagonal matrix A using the LU fac‐
torization computed by DGTTRF.
ARGUMENTS
TRANSA (input)
Specifies the form of the system of equations. = 'N': A * X
= B (No transpose)
= 'T': A'* X = B (Transpose)
= 'C': A'* X = B (Conjugate transpose = Transpose)
TRANSA is defaulted to 'N' for F95 INTERFACE.
N (input) The order of the matrix A.
NRHS (input)
The number of right hand sides, i.e., the number of columns
of the matrix B. NRHS >= 0.
LOW (input)
The (n-1) multipliers that define the matrix L from the LU
factorization of A.
D (input) The n diagonal elements of the upper triangular matrix U from
the LU factorization of A.
UP1 (input)
The (n-1) elements of the first super-diagonal of U.
UP2 (input)
The (n-2) elements of the second super-diagonal of U.
IPIVOT (input)
The pivot indices; for 1 <= i <= n, row i of the matrix was
interchanged with row IPIVOT(i). IPIVOT(i) will always be
either i or i+1; IPIVOT(i) = i indicates a row interchange
was not required.
B (input/output)
On entry, the matrix of right hand side vectors B. On exit,
B is overwritten by the solution vectors 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
6 Mar 2009 dgttrs(3P)
