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    1: *> \brief \b DGER
    2: *
    3: *  =========== DOCUMENTATION ===========
    4: *
    5: * Online html documentation available at
    6: *            http://www.netlib.org/lapack/explore-html/
    7: *
    8: *  Definition:
    9: *  ===========
   10: *
   11: *       SUBROUTINE DGER(M,N,ALPHA,X,INCX,Y,INCY,A,LDA)
   12: *
   13: *       .. Scalar Arguments ..
   14: *       DOUBLE PRECISION ALPHA
   15: *       INTEGER INCX,INCY,LDA,M,N
   16: *       ..
   17: *       .. Array Arguments ..
   18: *       DOUBLE PRECISION A(LDA,*),X(*),Y(*)
   19: *       ..
   20: *
   21: *
   22: *> \par Purpose:
   23: *  =============
   24: *>
   25: *> \verbatim
   26: *>
   27: *> DGER   performs the rank 1 operation
   28: *>
   29: *>    A := alpha*x*y**T + A,
   30: *>
   31: *> where alpha is a scalar, x is an m element vector, y is an n element
   32: *> vector and A is an m by n matrix.
   33: *> \endverbatim
   34: *
   35: *  Arguments:
   36: *  ==========
   37: *
   38: *> \param[in] M
   39: *> \verbatim
   40: *>          M is INTEGER
   41: *>           On entry, M specifies the number of rows of the matrix A.
   42: *>           M must be at least zero.
   43: *> \endverbatim
   44: *>
   45: *> \param[in] N
   46: *> \verbatim
   47: *>          N is INTEGER
   48: *>           On entry, N specifies the number of columns of the matrix A.
   49: *>           N must be at least zero.
   50: *> \endverbatim
   51: *>
   52: *> \param[in] ALPHA
   53: *> \verbatim
   54: *>          ALPHA is DOUBLE PRECISION.
   55: *>           On entry, ALPHA specifies the scalar alpha.
   56: *> \endverbatim
   57: *>
   58: *> \param[in] X
   59: *> \verbatim
   60: *>          X is DOUBLE PRECISION array, dimension at least
   61: *>           ( 1 + ( m - 1 )*abs( INCX ) ).
   62: *>           Before entry, the incremented array X must contain the m
   63: *>           element vector x.
   64: *> \endverbatim
   65: *>
   66: *> \param[in] INCX
   67: *> \verbatim
   68: *>          INCX is INTEGER
   69: *>           On entry, INCX specifies the increment for the elements of
   70: *>           X. INCX must not be zero.
   71: *> \endverbatim
   72: *>
   73: *> \param[in] Y
   74: *> \verbatim
   75: *>          Y is DOUBLE PRECISION array, dimension at least
   76: *>           ( 1 + ( n - 1 )*abs( INCY ) ).
   77: *>           Before entry, the incremented array Y must contain the n
   78: *>           element vector y.
   79: *> \endverbatim
   80: *>
   81: *> \param[in] INCY
   82: *> \verbatim
   83: *>          INCY is INTEGER
   84: *>           On entry, INCY specifies the increment for the elements of
   85: *>           Y. INCY must not be zero.
   86: *> \endverbatim
   87: *>
   88: *> \param[in,out] A
   89: *> \verbatim
   90: *>          A is DOUBLE PRECISION array, dimension ( LDA, N )
   91: *>           Before entry, the leading m by n part of the array A must
   92: *>           contain the matrix of coefficients. On exit, A is
   93: *>           overwritten by the updated matrix.
   94: *> \endverbatim
   95: *>
   96: *> \param[in] LDA
   97: *> \verbatim
   98: *>          LDA is INTEGER
   99: *>           On entry, LDA specifies the first dimension of A as declared
  100: *>           in the calling (sub) program. LDA must be at least
  101: *>           max( 1, m ).
  102: *> \endverbatim
  103: *
  104: *  Authors:
  105: *  ========
  106: *
  107: *> \author Univ. of Tennessee
  108: *> \author Univ. of California Berkeley
  109: *> \author Univ. of Colorado Denver
  110: *> \author NAG Ltd.
  111: *
  112: *> \date December 2016
  113: *
  114: *> \ingroup double_blas_level2
  115: *
  116: *> \par Further Details:
  117: *  =====================
  118: *>
  119: *> \verbatim
  120: *>
  121: *>  Level 2 Blas routine.
  122: *>
  123: *>  -- Written on 22-October-1986.
  124: *>     Jack Dongarra, Argonne National Lab.
  125: *>     Jeremy Du Croz, Nag Central Office.
  126: *>     Sven Hammarling, Nag Central Office.
  127: *>     Richard Hanson, Sandia National Labs.
  128: *> \endverbatim
  129: *>
  130: *  =====================================================================
  131:       SUBROUTINE DGER(M,N,ALPHA,X,INCX,Y,INCY,A,LDA)
  132: *
  133: *  -- Reference BLAS level2 routine (version 3.7.0) --
  134: *  -- Reference BLAS is a software package provided by Univ. of Tennessee,    --
  135: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
  136: *     December 2016
  137: *
  138: *     .. Scalar Arguments ..
  139:       DOUBLE PRECISION ALPHA
  140:       INTEGER INCX,INCY,LDA,M,N
  141: *     ..
  142: *     .. Array Arguments ..
  143:       DOUBLE PRECISION A(LDA,*),X(*),Y(*)
  144: *     ..
  145: *
  146: *  =====================================================================
  147: *
  148: *     .. Parameters ..
  149:       DOUBLE PRECISION ZERO
  150:       PARAMETER (ZERO=0.0D+0)
  151: *     ..
  152: *     .. Local Scalars ..
  153:       DOUBLE PRECISION TEMP
  154:       INTEGER I,INFO,IX,J,JY,KX
  155: *     ..
  156: *     .. External Subroutines ..
  157:       EXTERNAL XERBLA
  158: *     ..
  159: *     .. Intrinsic Functions ..
  160:       INTRINSIC MAX
  161: *     ..
  162: *
  163: *     Test the input parameters.
  164: *
  165:       INFO = 0
  166:       IF (M.LT.0) THEN
  167:           INFO = 1
  168:       ELSE IF (N.LT.0) THEN
  169:           INFO = 2
  170:       ELSE IF (INCX.EQ.0) THEN
  171:           INFO = 5
  172:       ELSE IF (INCY.EQ.0) THEN
  173:           INFO = 7
  174:       ELSE IF (LDA.LT.MAX(1,M)) THEN
  175:           INFO = 9
  176:       END IF
  177:       IF (INFO.NE.0) THEN
  178:           CALL XERBLA('DGER  ',INFO)
  179:           RETURN
  180:       END IF
  181: *
  182: *     Quick return if possible.
  183: *
  184:       IF ((M.EQ.0) .OR. (N.EQ.0) .OR. (ALPHA.EQ.ZERO)) RETURN
  185: *
  186: *     Start the operations. In this version the elements of A are
  187: *     accessed sequentially with one pass through A.
  188: *
  189:       IF (INCY.GT.0) THEN
  190:           JY = 1
  191:       ELSE
  192:           JY = 1 - (N-1)*INCY
  193:       END IF
  194:       IF (INCX.EQ.1) THEN
  195:           DO 20 J = 1,N
  196:               IF (Y(JY).NE.ZERO) THEN
  197:                   TEMP = ALPHA*Y(JY)
  198:                   DO 10 I = 1,M
  199:                       A(I,J) = A(I,J) + X(I)*TEMP
  200:    10             CONTINUE
  201:               END IF
  202:               JY = JY + INCY
  203:    20     CONTINUE
  204:       ELSE
  205:           IF (INCX.GT.0) THEN
  206:               KX = 1
  207:           ELSE
  208:               KX = 1 - (M-1)*INCX
  209:           END IF
  210:           DO 40 J = 1,N
  211:               IF (Y(JY).NE.ZERO) THEN
  212:                   TEMP = ALPHA*Y(JY)
  213:                   IX = KX
  214:                   DO 30 I = 1,M
  215:                       A(I,J) = A(I,J) + X(IX)*TEMP
  216:                       IX = IX + INCX
  217:    30             CONTINUE
  218:               END IF
  219:               JY = JY + INCY
  220:    40     CONTINUE
  221:       END IF
  222: *
  223:       RETURN
  224: *
  225: *     End of DGER  .
  226: *
  227:       END