NAME¶
SGEMV - perform one of the matrix-vector operations y := alpha*A*x + beta*y, or
y := alpha*A'*x + beta*y,
SYNOPSIS¶
- SUBROUTINE SGEMV
- ( TRANS, M, N, ALPHA, A, LDA, X, INCX, BETA, Y, INCY )
- REAL
- ALPHA, BETA
- INTEGER
- INCX, INCY, LDA, M, N
- CHARACTER*1
- TRANS
- REAL
- A( LDA, * ), X( * ), Y( * )
PURPOSE¶
SGEMV performs one of the matrix-vector operations
where alpha and beta are scalars, x and y are vectors and A is an m by n matrix.
PARAMETERS¶
- TRANS - 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'*x + beta*y.
TRANS = 'C' or 'c' y := alpha*A'*x + beta*y.
Unchanged on exit.
- M - INTEGER.
- On entry, M specifies the number of rows of the matrix A. M
must be at least zero. Unchanged on exit.
- N - INTEGER.
- On entry, N specifies the number of columns of the matrix
A. N must be at least zero. Unchanged on exit.
- ALPHA - REAL .
- On entry, ALPHA specifies the scalar alpha. Unchanged on
exit.
- A - REAL array of DIMENSION ( LDA, n ).
- Before entry, the leading m by n part of the array A must
contain the matrix of coefficients. Unchanged on exit.
- LDA - 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 ).
Unchanged on exit.
- X - REAL 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. Unchanged on exit.
- INCX - INTEGER.
- On entry, INCX specifies the increment for the elements of
X. INCX must not be zero. Unchanged on exit.
- BETA - REAL .
- On entry, BETA specifies the scalar beta. When BETA is
supplied as zero then Y need not be set on input. Unchanged on exit.
- Y - REAL 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.
- INCY - INTEGER.
- On entry, INCY specifies the increment for the elements of
Y. INCY must not be zero. Unchanged on exit.
Level 2 Blas routine.
-- 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.