.TH DSYR2 1 "November 2006" "BLAS routine" "BLAS routine" .SH NAME DSYR2 - the symmetric rank 2 operation A := alpha*x*y\(aq + alpha*y*x\(aq + A, .SH SYNOPSIS .TP 51 SUBROUTINE DSYR2(UPLO,N,ALPHA,X,INCX,Y,INCY,A,LDA) .TP 51 .ti +4 DOUBLE PRECISION ALPHA .TP 51 .ti +4 INTEGER INCX,INCY,LDA,N .TP 51 .ti +4 CHARACTER UPLO .TP 51 .ti +4 DOUBLE PRECISION A(LDA,*),X(*),Y(*) .SH PURPOSE DSYR2 performs the symmetric rank 2 operation where alpha is a scalar, x and y are n element vectors and A is an n by n symmetric matrix. .br .SH ARGUMENTS .TP 7 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 = \(aqU\(aq or \(aqu\(aq Only the upper triangular part of A is to be referenced. UPLO = \(aqL\(aq or \(aql\(aq Only the lower triangular part of A is to be referenced. Unchanged on exit. .TP 7 N - INTEGER. On entry, N specifies the order of the matrix A. N must be at least zero. Unchanged on exit. .TP 7 ALPHA - DOUBLE PRECISION. On entry, ALPHA specifies the scalar alpha. Unchanged on exit. .TP 7 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. .TP 7 INCX - INTEGER. On entry, INCX specifies the increment for the elements of X. INCX must not be zero. Unchanged on exit. .TP 7 Y - DOUBLE PRECISION array of dimension at least ( 1 + ( n - 1 )*abs( INCY ) ). Before entry, the incremented array Y must contain the n element vector y. Unchanged on exit. .TP 7 INCY - INTEGER. On entry, INCY specifies the increment for the elements of Y. INCY must not be zero. Unchanged on exit. .TP 7 A - DOUBLE PRECISION array of DIMENSION ( LDA, n ). Before entry with UPLO = \(aqU\(aq or \(aqu\(aq, 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 = \(aqL\(aq or \(aql\(aq, 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. .TP 7 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. 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.