*> \brief \b SSYMM
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at 
*            http://www.netlib.org/lapack/explore-html/ 
*
*  Definition:
*  ===========
*
*       SUBROUTINE SSYMM(SIDE,UPLO,M,N,ALPHA,A,LDA,B,LDB,BETA,C,LDC)
* 
*       .. Scalar Arguments ..
*       REAL ALPHA,BETA
*       INTEGER LDA,LDB,LDC,M,N
*       CHARACTER SIDE,UPLO
*       ..
*       .. Array Arguments ..
*       REAL A(LDA,*),B(LDB,*),C(LDC,*)
*       ..
*  
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> SSYMM  performs one of the matrix-matrix operations
*>
*>    C := alpha*A*B + beta*C,
*>
*> or
*>
*>    C := alpha*B*A + beta*C,
*>
*> where alpha and beta are scalars,  A is a symmetric matrix and  B and
*> C are  m by n matrices.
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] SIDE
*> \verbatim
*>          SIDE is CHARACTER*1
*>           On entry,  SIDE  specifies whether  the  symmetric matrix  A
*>           appears on the  left or right  in the  operation as follows:
*>
*>              SIDE = 'L' or 'l'   C := alpha*A*B + beta*C,
*>
*>              SIDE = 'R' or 'r'   C := alpha*B*A + beta*C,
*> \endverbatim
*>
*> \param[in] UPLO
*> \verbatim
*>          UPLO is CHARACTER*1
*>           On  entry,   UPLO  specifies  whether  the  upper  or  lower
*>           triangular  part  of  the  symmetric  matrix   A  is  to  be
*>           referenced as follows:
*>
*>              UPLO = 'U' or 'u'   Only the upper triangular part of the
*>                                  symmetric matrix is to be referenced.
*>
*>              UPLO = 'L' or 'l'   Only the lower triangular part of the
*>                                  symmetric matrix is to be referenced.
*> \endverbatim
*>
*> \param[in] M
*> \verbatim
*>          M is INTEGER
*>           On entry,  M  specifies the number of rows of the matrix  C.
*>           M  must be at least zero.
*> \endverbatim
*>
*> \param[in] N
*> \verbatim
*>          N is INTEGER
*>           On entry, N specifies the number of columns of the matrix C.
*>           N  must be at least zero.
*> \endverbatim
*>
*> \param[in] ALPHA
*> \verbatim
*>          ALPHA is REAL
*>           On entry, ALPHA specifies the scalar alpha.
*> \endverbatim
*>
*> \param[in] A
*> \verbatim
*>          A is REAL array of DIMENSION ( LDA, ka ), where ka is
*>           m  when  SIDE = 'L' or 'l'  and is  n otherwise.
*>           Before entry  with  SIDE = 'L' or 'l',  the  m by m  part of
*>           the array  A  must contain the  symmetric matrix,  such that
*>           when  UPLO = 'U' or 'u', the leading m by m 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,  and when  UPLO = 'L' or 'l',
*>           the leading  m by m  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.
*>           Before entry  with  SIDE = 'R' or 'r',  the  n by n  part of
*>           the array  A  must contain the  symmetric matrix,  such that
*>           when  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,  and when  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.
*> \endverbatim
*>
*> \param[in] LDA
*> \verbatim
*>          LDA is INTEGER
*>           On entry, LDA specifies the first dimension of A as declared
*>           in the calling (sub) program.  When  SIDE = 'L' or 'l'  then
*>           LDA must be at least  max( 1, m ), otherwise  LDA must be at
*>           least  max( 1, n ).
*> \endverbatim
*>
*> \param[in] B
*> \verbatim
*>          B is REAL array of DIMENSION ( LDB, n ).
*>           Before entry, the leading  m by n part of the array  B  must
*>           contain the matrix B.
*> \endverbatim
*>
*> \param[in] LDB
*> \verbatim
*>          LDB is INTEGER
*>           On entry, LDB specifies the first dimension of B as declared
*>           in  the  calling  (sub)  program.   LDB  must  be  at  least
*>           max( 1, m ).
*> \endverbatim
*>
*> \param[in] BETA
*> \verbatim
*>          BETA is REAL
*>           On entry,  BETA  specifies the scalar  beta.  When  BETA  is
*>           supplied as zero then C need not be set on input.
*> \endverbatim
*>
*> \param[in,out] C
*> \verbatim
*>          C is REAL array of DIMENSION ( LDC, n ).
*>           Before entry, the leading  m by n  part of the array  C must
*>           contain the matrix  C,  except when  beta  is zero, in which
*>           case C need not be set on entry.
*>           On exit, the array  C  is overwritten by the  m by n updated
*>           matrix.
*> \endverbatim
*>
*> \param[in] LDC
*> \verbatim
*>          LDC is INTEGER
*>           On entry, LDC specifies the first dimension of C as declared
*>           in  the  calling  (sub)  program.   LDC  must  be  at  least
*>           max( 1, m ).
*> \endverbatim
*
*  Authors:
*  ========
*
*> \author Univ. of Tennessee 
*> \author Univ. of California Berkeley 
*> \author Univ. of Colorado Denver 
*> \author NAG Ltd. 
*
*> \date November 2011
*
*> \ingroup single_blas_level3
*
*> \par Further Details:
*  =====================
*>
*> \verbatim
*>
*>  Level 3 Blas routine.
*>
*>  -- Written on 8-February-1989.
*>     Jack Dongarra, Argonne National Laboratory.
*>     Iain Duff, AERE Harwell.
*>     Jeremy Du Croz, Numerical Algorithms Group Ltd.
*>     Sven Hammarling, Numerical Algorithms Group Ltd.
*> \endverbatim
*>
*  =====================================================================
      SUBROUTINE SSYMM(SIDE,UPLO,M,N,ALPHA,A,LDA,B,LDB,BETA,C,LDC)
*
*  -- Reference BLAS level3 routine (version 3.4.0) --
*  -- Reference BLAS is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*     November 2011
*
*     .. Scalar Arguments ..
      REAL ALPHA,BETA
      INTEGER LDA,LDB,LDC,M,N
      CHARACTER SIDE,UPLO
*     ..
*     .. Array Arguments ..
      REAL A(LDA,*),B(LDB,*),C(LDC,*)
*     ..
*
*  =====================================================================
*
*     .. External Functions ..
      LOGICAL LSAME
      EXTERNAL LSAME
*     ..
*     .. External Subroutines ..
      EXTERNAL XERBLA
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC MAX
*     ..
*     .. Local Scalars ..
      REAL TEMP1,TEMP2
      INTEGER I,INFO,J,K,NROWA
      LOGICAL UPPER
*     ..
*     .. Parameters ..
      REAL ONE,ZERO
      PARAMETER (ONE=1.0E+0,ZERO=0.0E+0)
*     ..
*
*     Set NROWA as the number of rows of A.
*
      IF (LSAME(SIDE,'L')) THEN
          NROWA = M
      ELSE
          NROWA = N
      END IF
      UPPER = LSAME(UPLO,'U')
*
*     Test the input parameters.
*
      INFO = 0
      IF ((.NOT.LSAME(SIDE,'L')) .AND. (.NOT.LSAME(SIDE,'R'))) THEN
          INFO = 1
      ELSE IF ((.NOT.UPPER) .AND. (.NOT.LSAME(UPLO,'L'))) THEN
          INFO = 2
      ELSE IF (M.LT.0) THEN
          INFO = 3
      ELSE IF (N.LT.0) THEN
          INFO = 4
      ELSE IF (LDA.LT.MAX(1,NROWA)) THEN
          INFO = 7
      ELSE IF (LDB.LT.MAX(1,M)) THEN
          INFO = 9
      ELSE IF (LDC.LT.MAX(1,M)) THEN
          INFO = 12
      END IF
      IF (INFO.NE.0) THEN
          CALL XERBLA('SSYMM ',INFO)
          RETURN
      END IF
*
*     Quick return if possible.
*
      IF ((M.EQ.0) .OR. (N.EQ.0) .OR.
     +    ((ALPHA.EQ.ZERO).AND. (BETA.EQ.ONE))) RETURN
*
*     And when  alpha.eq.zero.
*
      IF (ALPHA.EQ.ZERO) THEN
          IF (BETA.EQ.ZERO) THEN
              DO 20 J = 1,N
                  DO 10 I = 1,M
                      C(I,J) = ZERO
   10             CONTINUE
   20         CONTINUE
          ELSE
              DO 40 J = 1,N
                  DO 30 I = 1,M
                      C(I,J) = BETA*C(I,J)
   30             CONTINUE
   40         CONTINUE
          END IF
          RETURN
      END IF
*
*     Start the operations.
*
      IF (LSAME(SIDE,'L')) THEN
*
*        Form  C := alpha*A*B + beta*C.
*
          IF (UPPER) THEN
              DO 70 J = 1,N
                  DO 60 I = 1,M
                      TEMP1 = ALPHA*B(I,J)
                      TEMP2 = ZERO
                      DO 50 K = 1,I - 1
                          C(K,J) = C(K,J) + TEMP1*A(K,I)
                          TEMP2 = TEMP2 + B(K,J)*A(K,I)
   50                 CONTINUE
                      IF (BETA.EQ.ZERO) THEN
                          C(I,J) = TEMP1*A(I,I) + ALPHA*TEMP2
                      ELSE
                          C(I,J) = BETA*C(I,J) + TEMP1*A(I,I) +
     +                             ALPHA*TEMP2
                      END IF
   60             CONTINUE
   70         CONTINUE
          ELSE
              DO 100 J = 1,N
                  DO 90 I = M,1,-1
                      TEMP1 = ALPHA*B(I,J)
                      TEMP2 = ZERO
                      DO 80 K = I + 1,M
                          C(K,J) = C(K,J) + TEMP1*A(K,I)
                          TEMP2 = TEMP2 + B(K,J)*A(K,I)
   80                 CONTINUE
                      IF (BETA.EQ.ZERO) THEN
                          C(I,J) = TEMP1*A(I,I) + ALPHA*TEMP2
                      ELSE
                          C(I,J) = BETA*C(I,J) + TEMP1*A(I,I) +
     +                             ALPHA*TEMP2
                      END IF
   90             CONTINUE
  100         CONTINUE
          END IF
      ELSE
*
*        Form  C := alpha*B*A + beta*C.
*
          DO 170 J = 1,N
              TEMP1 = ALPHA*A(J,J)
              IF (BETA.EQ.ZERO) THEN
                  DO 110 I = 1,M
                      C(I,J) = TEMP1*B(I,J)
  110             CONTINUE
              ELSE
                  DO 120 I = 1,M
                      C(I,J) = BETA*C(I,J) + TEMP1*B(I,J)
  120             CONTINUE
              END IF
              DO 140 K = 1,J - 1
                  IF (UPPER) THEN
                      TEMP1 = ALPHA*A(K,J)
                  ELSE
                      TEMP1 = ALPHA*A(J,K)
                  END IF
                  DO 130 I = 1,M
                      C(I,J) = C(I,J) + TEMP1*B(I,K)
  130             CONTINUE
  140         CONTINUE
              DO 160 K = J + 1,N
                  IF (UPPER) THEN
                      TEMP1 = ALPHA*A(J,K)
                  ELSE
                      TEMP1 = ALPHA*A(K,J)
                  END IF
                  DO 150 I = 1,M
                      C(I,J) = C(I,J) + TEMP1*B(I,K)
  150             CONTINUE
  160         CONTINUE
  170     CONTINUE
      END IF
*
      RETURN
*
*     End of SSYMM .
*
      END
