dtbmv(3P) Sun Performance Library dtbmv(3P)NAMEdtbmv - perform one of the matrix-vector operations x := A*x, or x :=
A'*x
SYNOPSIS
SUBROUTINE DTBMV(UPLO, TRANSA, DIAG, N, K, A, LDA, Y, INCY)
CHARACTER * 1 UPLO, TRANSA, DIAG
INTEGER N, K, LDA, INCY
DOUBLE PRECISION A(LDA,*), Y(*)
SUBROUTINE DTBMV_64(UPLO, TRANSA, DIAG, N, K, A, LDA, Y, INCY)
CHARACTER * 1 UPLO, TRANSA, DIAG
INTEGER*8 N, K, LDA, INCY
DOUBLE PRECISION A(LDA,*), Y(*)
F95 INTERFACE
SUBROUTINE TBMV(UPLO, [TRANSA], DIAG, [N], K, A, [LDA], Y, [INCY])
CHARACTER(LEN=1) :: UPLO, TRANSA, DIAG
INTEGER :: N, K, LDA, INCY
REAL(8), DIMENSION(:) :: Y
REAL(8), DIMENSION(:,:) :: A
SUBROUTINE TBMV_64(UPLO, [TRANSA], DIAG, [N], K, A, [LDA], Y,
[INCY])
CHARACTER(LEN=1) :: UPLO, TRANSA, DIAG
INTEGER(8) :: N, K, LDA, INCY
REAL(8), DIMENSION(:) :: Y
REAL(8), DIMENSION(:,:) :: A
C INTERFACE
#include <sunperf.h>
void dtbmv(char uplo, char transa, char diag, int n, int k, double *a,
int lda, double *y, int incy);
void dtbmv_64(char uplo, char transa, char diag, long n, long k, double
*a, long lda, double *y, long incy);
PURPOSEdtbmv performs one of the matrix-vector operations x := A*x, or x :=
A'*x, where x is an n element vector and A is an n by n unit, or non-
unit, upper or lower triangular band matrix, with ( k + 1 ) diagonals.
ARGUMENTS
UPLO (input)
On entry, UPLO specifies whether the matrix is an upper or
lower triangular matrix as follows:
UPLO = 'U' or 'u' A is an upper triangular matrix.
UPLO = 'L' or 'l' A is a lower triangular matrix.
Unchanged on exit.
TRANSA (input)
On entry, TRANSA specifies the operation to be performed as
follows:
TRANSA = 'N' or 'n' x := A*x.
TRANSA = 'T' or 't' x := A'*x.
TRANSA = 'C' or 'c' x := A'*x.
Unchanged on exit.
TRANSA is defaulted to 'N' for F95 INTERFACE.
DIAG (input)
On entry, DIAG specifies whether or not A is unit triangular
as follows:
DIAG = 'U' or 'u' A is assumed to be unit triangular.
DIAG = 'N' or 'n' A is not assumed to be unit triangular.
Unchanged on exit.
N (input)
On entry, N specifies the order of the matrix A. N >= 0.
Unchanged on exit.
K (input)
On entry with UPLO = 'U' or 'u', K specifies the number of
super-diagonals of the matrix A. On entry with UPLO = 'L' or
'l', K specifies the number of sub-diagonals of the matrix A.
K >= 0. Unchanged on exit.
A (input)
Before entry with UPLO = 'U' or 'u', the leading ( k + 1 ) by
n part of the array A must contain the upper triangular band
part of the matrix of coefficients, supplied column by col‐
umn, with the leading diagonal of the matrix in row ( k + 1 )
of the array, the first super-diagonal starting at position 2
in row k, and so on. The top left k by k triangle of the
array A is not referenced. The following program segment
will transfer an upper triangular band matrix from conven‐
tional full matrix storage to band storage:
DO 20, J = 1, N
M = K + 1 - J
DO 10, I = MAX( 1, J - K ), J
A( M + I, J ) = matrix( I, J )
10 CONTINUE
20 CONTINUE
Before entry with UPLO = 'L' or 'l', the leading ( k + 1 ) by
n part of the array A must contain the lower triangular band
part of the matrix of coefficients, supplied column by col‐
umn, with the leading diagonal of the matrix in row 1 of the
array, the first sub-diagonal starting at position 1 in row
2, and so on. The bottom right k by k triangle of the array A
is not referenced. The following program segment will trans‐
fer a lower triangular band matrix from conventional full
matrix storage to band storage:
DO 20, J = 1, N
M = 1 - J
DO 10, I = J, MIN( N, J + K )
A( M + I, J ) = matrix( I, J )
10 CONTINUE
20 CONTINUE
Note that when DIAG = 'U' or 'u' the elements of the array A
corresponding to the diagonal elements of the matrix are not
referenced, but are assumed to be unity. Unchanged on exit.
LDA (input)
On entry, LDA specifies the first dimension of A as declared
in the calling (sub) program. LDA >= ( k + 1 ). Unchanged on
exit.
Y (input/output)
( 1 + ( n - 1 )*abs( INCY ) ). Before entry, the incremented
array Y must contain the n element vector x. On exit, Y is
overwritten with the tranformed vector x.
INCY (input)
On entry, INCY specifies the increment for the elements of Y.
INCY <> 0. Unchanged on exit.
6 Mar 2009 dtbmv(3P)
