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SUBROUTINE <a name="DSYR2.1"></a><a href="dsyr2.f.html#DSYR2.1">DSYR2</a>(UPLO,N,ALPHA,X,INCX,Y,INCY,A,LDA)
<span class="comment">*</span><span class="comment"> .. Scalar Arguments ..
</span> DOUBLE PRECISION ALPHA
INTEGER INCX,INCY,LDA,N
CHARACTER UPLO
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Array Arguments ..
</span> DOUBLE PRECISION A(LDA,*),X(*),Y(*)
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Purpose
</span><span class="comment">*</span><span class="comment"> =======
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> <a name="DSYR2.14"></a><a href="dsyr2.f.html#DSYR2.1">DSYR2</a> performs the symmetric rank 2 operation
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> A := alpha*x*y' + alpha*y*x' + A,
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> where alpha is a scalar, x and y are n element vectors and A is an n
</span><span class="comment">*</span><span class="comment"> by n symmetric matrix.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Arguments
</span><span class="comment">*</span><span class="comment"> ==========
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> UPLO - CHARACTER*1.
</span><span class="comment">*</span><span class="comment"> On entry, UPLO specifies whether the upper or lower
</span><span class="comment">*</span><span class="comment"> triangular part of the array A is to be referenced as
</span><span class="comment">*</span><span class="comment"> follows:
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> UPLO = 'U' or 'u' Only the upper triangular part of A
</span><span class="comment">*</span><span class="comment"> is to be referenced.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> UPLO = 'L' or 'l' Only the lower triangular part of A
</span><span class="comment">*</span><span class="comment"> is to be referenced.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Unchanged on exit.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> N - INTEGER.
</span><span class="comment">*</span><span class="comment"> On entry, N specifies the order of the matrix A.
</span><span class="comment">*</span><span class="comment"> N must be at least zero.
</span><span class="comment">*</span><span class="comment"> Unchanged on exit.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> ALPHA - DOUBLE PRECISION.
</span><span class="comment">*</span><span class="comment"> On entry, ALPHA specifies the scalar alpha.
</span><span class="comment">*</span><span class="comment"> Unchanged on exit.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> X - DOUBLE PRECISION array of dimension at least
</span><span class="comment">*</span><span class="comment"> ( 1 + ( n - 1 )*abs( INCX ) ).
</span><span class="comment">*</span><span class="comment"> Before entry, the incremented array X must contain the n
</span><span class="comment">*</span><span class="comment"> element vector x.
</span><span class="comment">*</span><span class="comment"> Unchanged on exit.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> INCX - INTEGER.
</span><span class="comment">*</span><span class="comment"> On entry, INCX specifies the increment for the elements of
</span><span class="comment">*</span><span class="comment"> X. INCX must not be zero.
</span><span class="comment">*</span><span class="comment"> Unchanged on exit.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Y - DOUBLE PRECISION array of dimension at least
</span><span class="comment">*</span><span class="comment"> ( 1 + ( n - 1 )*abs( INCY ) ).
</span><span class="comment">*</span><span class="comment"> Before entry, the incremented array Y must contain the n
</span><span class="comment">*</span><span class="comment"> element vector y.
</span><span class="comment">*</span><span class="comment"> Unchanged on exit.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> INCY - INTEGER.
</span><span class="comment">*</span><span class="comment"> On entry, INCY specifies the increment for the elements of
</span><span class="comment">*</span><span class="comment"> Y. INCY must not be zero.
</span><span class="comment">*</span><span class="comment"> Unchanged on exit.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> A - DOUBLE PRECISION array of DIMENSION ( LDA, n ).
</span><span class="comment">*</span><span class="comment"> Before entry with UPLO = 'U' or 'u', the leading n by n
</span><span class="comment">*</span><span class="comment"> upper triangular part of the array A must contain the upper
</span><span class="comment">*</span><span class="comment"> triangular part of the symmetric matrix and the strictly
</span><span class="comment">*</span><span class="comment"> lower triangular part of A is not referenced. On exit, the
</span><span class="comment">*</span><span class="comment"> upper triangular part of the array A is overwritten by the
</span><span class="comment">*</span><span class="comment"> upper triangular part of the updated matrix.
</span><span class="comment">*</span><span class="comment"> Before entry with UPLO = 'L' or 'l', the leading n by n
</span><span class="comment">*</span><span class="comment"> lower triangular part of the array A must contain the lower
</span><span class="comment">*</span><span class="comment"> triangular part of the symmetric matrix and the strictly
</span><span class="comment">*</span><span class="comment"> upper triangular part of A is not referenced. On exit, the
</span><span class="comment">*</span><span class="comment"> lower triangular part of the array A is overwritten by the
</span><span class="comment">*</span><span class="comment"> lower triangular part of the updated matrix.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> LDA - INTEGER.
</span><span class="comment">*</span><span class="comment"> On entry, LDA specifies the first dimension of A as declared
</span><span class="comment">*</span><span class="comment"> in the calling (sub) program. LDA must be at least
</span><span class="comment">*</span><span class="comment"> max( 1, n ).
</span><span class="comment">*</span><span class="comment"> Unchanged on exit.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Level 2 Blas routine.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> -- Written on 22-October-1986.
</span><span class="comment">*</span><span class="comment"> Jack Dongarra, Argonne National Lab.
</span><span class="comment">*</span><span class="comment"> Jeremy Du Croz, Nag Central Office.
</span><span class="comment">*</span><span class="comment"> Sven Hammarling, Nag Central Office.
</span><span class="comment">*</span><span class="comment"> Richard Hanson, Sandia National Labs.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> .. Parameters ..
</span> DOUBLE PRECISION ZERO
PARAMETER (ZERO=0.0D+0)
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Local Scalars ..
</span> DOUBLE PRECISION TEMP1,TEMP2
INTEGER I,INFO,IX,IY,J,JX,JY,KX,KY
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. External Functions ..
</span> LOGICAL <a name="LSAME.107"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
EXTERNAL <a name="LSAME.108"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
<span class="comment">*</span><span class="comment"> ..
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