.TH SSPR2 1 "November 2006" "BLAS routine" "BLAS routine" .SH NAME SSPR2 - the symmetric rank 2 operation A := alpha*x*y\(aq + alpha*y*x\(aq + A, .SH SYNOPSIS .TP 48 SUBROUTINE SSPR2(UPLO,N,ALPHA,X,INCX,Y,INCY,AP) .TP 48 .ti +4 REAL ALPHA .TP 48 .ti +4 INTEGER INCX,INCY,N .TP 48 .ti +4 CHARACTER UPLO .TP 48 .ti +4 REAL AP(*),X(*),Y(*) .SH PURPOSE SSPR2 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, supplied in packed form. .br .SH ARGUMENTS .TP 7 UPLO - CHARACTER*1. On entry, UPLO specifies whether the upper or lower triangular part of the matrix A is supplied in the packed array AP as follows: UPLO = \(aqU\(aq or \(aqu\(aq The upper triangular part of A is supplied in AP. UPLO = \(aqL\(aq or \(aql\(aq The lower triangular part of A is supplied in AP. 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 - REAL . On entry, ALPHA specifies the scalar alpha. Unchanged on exit. .TP 7 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. .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 - REAL 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 AP - REAL array of DIMENSION at least ( ( n*( n + 1 ) )/2 ). Before entry with UPLO = \(aqU\(aq or \(aqu\(aq, the array AP must contain the upper triangular part of the symmetric matrix packed sequentially, column by column, so that AP( 1 ) contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 1, 2 ) and a( 2, 2 ) respectively, and so on. On exit, the array AP is overwritten by the upper triangular part of the updated matrix. Before entry with UPLO = \(aqL\(aq or \(aql\(aq, the array AP must contain the lower triangular part of the symmetric matrix packed sequentially, column by column, so that AP( 1 ) contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 2, 1 ) and a( 3, 1 ) respectively, and so on. On exit, the array AP is overwritten by the lower triangular part of the updated matrix. 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.