sgbtrs(3P) Sun Performance Library sgbtrs(3P)NAMEsgbtrs - solve a system of linear equations A * X = B or A' * X = B
with a general band matrix A using the LU factorization computed by
SGBTRF
SYNOPSIS
SUBROUTINE SGBTRS(TRANSA, N, KL, KU, NRHS, A, LDA, IPIVOT, B,
LDB, INFO)
CHARACTER * 1 TRANSA
INTEGER N, KL, KU, NRHS, LDA, LDB, INFO
INTEGER IPIVOT(*)
REAL A(LDA,*), B(LDB,*)
SUBROUTINE SGBTRS_64(TRANSA, N, KL, KU, NRHS, A, LDA, IPIVOT,
B, LDB, INFO)
CHARACTER * 1 TRANSA
INTEGER*8 N, KL, KU, NRHS, LDA, LDB, INFO
INTEGER*8 IPIVOT(*)
REAL A(LDA,*), B(LDB,*)
F95 INTERFACE
SUBROUTINE GBTRS([TRANSA], [N], KL, KU, [NRHS], A, [LDA],
IPIVOT, B, [LDB], [INFO])
CHARACTER(LEN=1) :: TRANSA
INTEGER :: N, KL, KU, NRHS, LDA, LDB, INFO
INTEGER, DIMENSION(:) :: IPIVOT
REAL, DIMENSION(:,:) :: A, B
SUBROUTINE GBTRS_64([TRANSA], [N], KL, KU, [NRHS], A, [LDA],
IPIVOT, B, [LDB], [INFO])
CHARACTER(LEN=1) :: TRANSA
INTEGER(8) :: N, KL, KU, NRHS, LDA, LDB, INFO
INTEGER(8), DIMENSION(:) :: IPIVOT
REAL, DIMENSION(:,:) :: A, B
C INTERFACE
#include <sunperf.h>
void sgbtrs(char transa, int n, int kl, int ku, int nrhs, float *a, int
lda, int *ipivot, float *b, int ldb, int *info);
void sgbtrs_64(char transa, long n, long kl, long ku, long nrhs, float
*a, long lda, long *ipivot, float *b, long ldb, long *info);
PURPOSEsgbtrs solves a system of linear equations
A * X = B or A' * X = B with a general band matrix A using the LU
factorization computed by SGBTRF.
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. N >= 0.
KL (input)
The number of subdiagonals within the band of A. KL >= 0.
KU (input)
The number of superdiagonals within the band of A. KU >= 0.
NRHS (input)
The number of right hand sides, i.e., the number of columns
of the matrix B. NRHS >= 0.
A (input) Details of the LU factorization of the band matrix A, as com‐
puted by SGBTRF. U is stored as an upper triangular band
matrix with KL+KU superdiagonals in rows 1 to KL+KU+1, and
the multipliers used during the factorization are stored in
rows KL+KU+2 to 2*KL+KU+1.
LDA (input)
The leading dimension of the array A. LDA >= 2*KL+KU+1.
IPIVOT (input)
The pivot indices; for 1 <= i <= N, row i of the matrix was
interchanged with row IPIVOT(i).
B (input/output)
On entry, the right hand side matrix B. On exit, the solu‐
tion 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
6 Mar 2009 sgbtrs(3P)
