SSYMV
Purpose
SSYMV performs the matrix-vector operation
y := alpha*A*x + beta*y,
where alpha and beta are scalars, x and y are n element vectors and
A is an n by n symmetric matrix.
y := alpha*A*x + beta*y,
where alpha and beta are scalars, x and y are n element vectors and
A is an n by n symmetric matrix.
Arguments
| UPLO |
CHARACTER*1.
On entry, UPLO specifies whether the upper or lower
triangular part of the array A is to be referenced as follows: UPLO = 'U' or 'u' Only the upper triangular part of A is to be referenced. UPLO = 'L' or 'l' Only the lower triangular part of A is to be referenced. Unchanged on exit. |
| N |
INTEGER.
On entry, N specifies the order 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 with UPLO = 'U' or 'u', the leading n by n
upper triangular part of the array A must contain the upper triangular part of the symmetric matrix and the strictly lower triangular part of A is not referenced. Before entry with UPLO = 'L' or 'l', the leading n by n lower triangular part of the array A must contain the lower triangular part of the symmetric matrix and the strictly upper triangular part of A is not referenced. 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, n ). Unchanged on exit. |
| X |
REAL array of dimension at least
( 1 + ( n - 1 )*abs( INCX ) ).
Before entry, the incremented array X must contain the n element 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 + ( n - 1 )*abs( INCY ) ).
Before entry, the incremented array Y must contain the n element 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. |
Further Details
Level 2 Blas routine.
The vector and matrix arguments are not referenced when N = 0, or M = 0
Jack Dongarra, Argonne National Lab.
Jeremy Du Croz, Nag Central Office.
Sven Hammarling, Nag Central Office.
Richard Hanson, Sandia National Labs.
The vector and matrix arguments are not referenced when N = 0, or M = 0
Jack Dongarra, Argonne National Lab.
Jeremy Du Croz, Nag Central Office.
Sven Hammarling, Nag Central Office.
Richard Hanson, Sandia National Labs.