LAPACK
3.5.0
LAPACK: Linear Algebra PACKage

Go to the source code of this file.
Functions/Subroutines  
subroutine  dgbmv (TRANS, M, N, KL, KU, ALPHA, A, LDA, X, INCX, BETA, Y, INCY) 
DGBMV More...  
subroutine dgbmv  (  character  TRANS, 
integer  M,  
integer  N,  
integer  KL,  
integer  KU,  
double precision  ALPHA,  
double precision, dimension(lda,*)  A,  
integer  LDA,  
double precision, dimension(*)  X,  
integer  INCX,  
double precision  BETA,  
double precision, dimension(*)  Y,  
integer  INCY  
) 
DGBMV
DGBMV performs one of the matrixvector operations y := alpha*A*x + beta*y, or y := alpha*A**T*x + beta*y, where alpha and beta are scalars, x and y are vectors and A is an m by n band matrix, with kl subdiagonals and ku superdiagonals.
[in]  TRANS  TRANS is CHARACTER*1 On entry, TRANS specifies the operation to be performed as follows: TRANS = 'N' or 'n' y := alpha*A*x + beta*y. TRANS = 'T' or 't' y := alpha*A**T*x + beta*y. TRANS = 'C' or 'c' y := alpha*A**T*x + beta*y. 
[in]  M  M is INTEGER On entry, M specifies the number of rows of the matrix A. M must be at least zero. 
[in]  N  N is INTEGER On entry, N specifies the number of columns of the matrix A. N must be at least zero. 
[in]  KL  KL is INTEGER On entry, KL specifies the number of subdiagonals of the matrix A. KL must satisfy 0 .le. KL. 
[in]  KU  KU is INTEGER On entry, KU specifies the number of superdiagonals of the matrix A. KU must satisfy 0 .le. KU. 
[in]  ALPHA  ALPHA is DOUBLE PRECISION. On entry, ALPHA specifies the scalar alpha. 
[in]  A  A is DOUBLE PRECISION array of DIMENSION ( LDA, n ). Before entry, the leading ( kl + ku + 1 ) by n part of the array A must contain the matrix of coefficients, supplied column by column, with the leading diagonal of the matrix in row ( ku + 1 ) of the array, the first superdiagonal starting at position 2 in row ku, the first subdiagonal starting at position 1 in row ( ku + 2 ), and so on. Elements in the array A that do not correspond to elements in the band matrix (such as the top left ku by ku triangle) are not referenced. The following program segment will transfer a band matrix from conventional full matrix storage to band storage: DO 20, J = 1, N K = KU + 1  J DO 10, I = MAX( 1, J  KU ), MIN( M, J + KL ) A( K + I, J ) = matrix( I, J ) 10 CONTINUE 20 CONTINUE 
[in]  LDA  LDA is INTEGER On entry, LDA specifies the first dimension of A as declared in the calling (sub) program. LDA must be at least ( kl + ku + 1 ). 
[in]  X  X is DOUBLE PRECISION array of DIMENSION at least ( 1 + ( n  1 )*abs( INCX ) ) when TRANS = 'N' or 'n' and at least ( 1 + ( m  1 )*abs( INCX ) ) otherwise. Before entry, the incremented array X must contain the vector x. 
[in]  INCX  INCX is INTEGER On entry, INCX specifies the increment for the elements of X. INCX must not be zero. 
[in]  BETA  BETA is DOUBLE PRECISION. On entry, BETA specifies the scalar beta. When BETA is supplied as zero then Y need not be set on input. 
[in,out]  Y  Y is DOUBLE PRECISION array of DIMENSION at least ( 1 + ( m  1 )*abs( INCY ) ) when TRANS = 'N' or 'n' and at least ( 1 + ( n  1 )*abs( INCY ) ) otherwise. Before entry, the incremented array Y must contain the vector y. On exit, Y is overwritten by the updated vector y. 
[in]  INCY  INCY is INTEGER On entry, INCY specifies the increment for the elements of Y. INCY must not be zero. 
Level 2 Blas routine. The vector and matrix arguments are not referenced when N = 0, or M = 0  Written on 22October1986. Jack Dongarra, Argonne National Lab. Jeremy Du Croz, Nag Central Office. Sven Hammarling, Nag Central Office. Richard Hanson, Sandia National Labs.
Definition at line 186 of file dgbmv.f.