dsyr (l) - Linux Manuals
dsyr: performs the symmetric rank 1 operation A := alpha*x*xaq + A,
NAME
DSYR - performs the symmetric rank 1 operation A := alpha*x*xaq + A,SYNOPSIS
- SUBROUTINE DSYR(UPLO,N,ALPHA,X,INCX,A,LDA)
- DOUBLE PRECISION ALPHA
- INTEGER INCX,LDA,N
- CHARACTER UPLO
- DOUBLE PRECISION A(LDA,*),X(*)
PURPOSE
DSYR performs the symmetric rank 1 operation
where alpha is a real scalar, x is an n element vector 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 = aqUaq or aquaq Only the upper triangular part of A is to be referenced.
UPLO = aqLaq or aqlaq 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 - DOUBLE PRECISION.
- On entry, ALPHA specifies the scalar alpha. Unchanged on exit.
- X - DOUBLE PRECISION 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.
- A - DOUBLE PRECISION array of DIMENSION ( LDA, n ).
- Before entry with UPLO = aqUaq or aquaq, 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. On exit, the upper triangular part of the array A is overwritten by the upper triangular part of the updated matrix. Before entry with UPLO = aqLaq or aqlaq, 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. On exit, the lower triangular part of the array A is overwritten by the lower triangular part of the updated matrix.
- 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.
FURTHER DETAILS
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.