SUBROUTINECSYRF(UPLO,N,ALPHA,X,INCX,A,LDA)
*
*--LAPACKauxiliaryroutine(version3.1)--
*Univ.ofTennessee,Univ.ofCaliforniaBerkeleyandNAGLtd..
*November2006
*
*..ScalarArguments..
CHARACTERUPLO
INTEGERINCX,LDA,N
COMPLEXALPHA
*..
*..ArrayArguments..
COMPLEXA(LDA,*),X(*)
*..
*
*Purpose
*=======
*
*CSYRperformsthesymmetricrank1operation
*
*A:=alpha*x*(x' ) + A,
*
* where alpha is a complex scalar, x is an n element vector and A is an
* n by n symmetric matrix.
*
* Arguments
* ==========
*
* UPLO (input) 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 (input) INTEGER
* On entry, N specifies the order of the matrix A.
* N must be at least zero.
* Unchanged on exit.
*
* ALPHA (input) COMPLEX
* On entry, ALPHA specifies the scalar alpha.
* Unchanged on exit.
*
* X (input) COMPLEX array, 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 (input) INTEGER
* On entry, INCX specifies the increment for the elements of
* X. INCX must not be zero.
* Unchanged on exit.
*
* A (input/output) COMPLEX array, 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. 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 = '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. On exit, the
* lower triangular part of the array A is overwritten by the
* lower triangular part of the updated matrix.
*
* LDA (input) 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.
*
* =====================================================================
*
* .. Parameters ..
 COMPLEX ZERO
 PARAMETER ( ZERO = ( 0.0E+0, 0.0E+0 ) )
* ..
* .. Local Scalars ..
 INTEGER I, INFO, IX, J, JX, KX
 COMPLEX TEMP
* ..
* .. External Functions ..
 LOGICAL LSAME
 EXTERNAL LSAME
* ..
* .. External Subroutines ..
 EXTERNAL XERBLA
* ..
* .. Intrinsic Functions ..
 INTRINSIC MAX
* ..
* .. Executable Statements ..
*
* Test the input parameters.
*
 INFO = 0
 IF( .NOT.LSAME( UPLO, 'U' ) .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
 INFO = 1
 ELSE IF( N.LT.0 ) THEN
 INFO = 2
 ELSE IF( INCX.EQ.0 ) THEN
 INFO = 5
 ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
 INFO = 7
 END IF
 IF( INFO.NE.0 ) THEN
 CALL XERBLA( 'CSYR', INFO )
 RETURN
 END IF
*
* Quick return if possible.
*
 IF( ( N.EQ.0 ) .OR. ( ALPHA.EQ.ZERO ) )
 $ RETURN
*
* Set the start point in X if the increment is not unity.
*
 IF( INCX.LE.0 ) THEN
 KX = 1 - ( N-1 )*INCX
 ELSE IF( INCX.NE.1 ) THEN
 KX = 1
 END IF
*
* Start the operations. In this version the elements of A are
* accessed sequentially with one pass through the triangular part
* of A.
*
 IF( LSAME( UPLO, 'U' ) ) THEN
*
* Form A when A is stored in upper triangle.
*
 IF( INCX.EQ.1 ) THEN
 DO 20 J = 1, N
 IF( X( J ).NE.ZERO ) THEN
 TEMP = ALPHA*X( J )
 DO 10 I = 1, J
 A( I, J ) = A( I, J ) + X( I )*TEMP
 10 CONTINUE
 END IF
 20 CONTINUE
 ELSE
 JX = KX
 DO 40 J = 1, N
 IF( X( JX ).NE.ZERO ) THEN
 TEMP = ALPHA*X( JX )
 IX = KX
 DO 30 I = 1, J
 A( I, J ) = A( I, J ) + X( IX )*TEMP
 IX = IX + INCX
 30 CONTINUE
 END IF
 JX = JX + INCX
 40 CONTINUE
 END IF
 ELSE
*
* Form A when A is stored in lower triangle.
*
 IF( INCX.EQ.1 ) THEN
 DO 60 J = 1, N
 IF( X( J ).NE.ZERO ) THEN
 TEMP = ALPHA*X( J )
 DO 50 I = J, N
 A( I, J ) = A( I, J ) + X( I )*TEMP
 50 CONTINUE
 END IF
 60 CONTINUE
 ELSE
 JX = KX
 DO 80 J = 1, N
 IF( X( JX ).NE.ZERO ) THEN
 TEMP = ALPHA*X( JX )
 IX = JX
 DO 70 I = J, N
 A( I, J ) = A( I, J ) + X( IX )*TEMP
 IX = IX + INCX
 70 CONTINUE
 END IF
 JX = JX + INCX
 80 CONTINUE
 END IF
 END IF
*
 RETURN
*
* End of CSYR
*
 END