Annotation of rpl/lapack/blas/dger.f, revision 1.10

1.8       bertrand    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 of 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 of 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 of 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 November 2011
                    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: *  =====================================================================
1.1       bertrand  131:       SUBROUTINE DGER(M,N,ALPHA,X,INCX,Y,INCY,A,LDA)
1.8       bertrand  132: *
                    133: *  -- Reference BLAS level2 routine (version 3.4.0) --
                    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: *     November 2011
                    137: *
1.1       bertrand  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

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