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LAPACK
3.7.0
LAPACK: Linear Algebra PACKage
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subroutine dgemv | ( | character | TRANS, |
integer | M, | ||
integer | N, | ||
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 | ||
) |
DGEMV
DGEMV performs one of the matrix-vector 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 matrix.
[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] | 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 m by n part of the array A must contain the matrix of coefficients. |
[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 max( 1, m ). |
[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 with BETA non-zero, 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 22-October-1986. Jack Dongarra, Argonne National Lab. Jeremy Du Croz, Nag Central Office. Sven Hammarling, Nag Central Office. Richard Hanson, Sandia National Labs.
Definition at line 158 of file dgemv.f.