1DGEMV(1)                         BLAS routine                         DGEMV(1)
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NAME

6       DGEMV  - one of the matrix-vector operations   y := alpha*A*x + beta*y,
7       or y := alpha*A'*x + beta*y,
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SYNOPSIS

10       SUBROUTINE DGEMV(TRANS,M,N,ALPHA,A,LDA,X,INCX,BETA,Y,INCY)
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12           DOUBLE                                                 PRECISION
13                                                                  ALPHA,BETA
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15           INTEGER                                                INCX,INCY,LDA,M,N
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17           CHARACTER                                              TRANS
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19           DOUBLE                                                 PRECISION
20                                                                  A(LDA,*),X(*),Y(*)
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PURPOSE

23       DGEMV  performs one of the matrix-vector operations
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25       where alpha and beta are scalars, x and y are vectors and A is an m  by
26       n matrix.
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ARGUMENTS

30       TRANS  - CHARACTER*1.
31              On  entry, TRANS specifies the operation to be performed as fol‐
32              lows:
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34              TRANS = 'N' or 'n'   y := alpha*A*x + beta*y.
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36              TRANS = 'T' or 't'   y := alpha*A'*x + beta*y.
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38              TRANS = 'C' or 'c'   y := alpha*A'*x + beta*y.
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40              Unchanged on exit.
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42       M      - INTEGER.
43              On entry, M specifies the number of rows of  the  matrix  A.   M
44              must be at least zero.  Unchanged on exit.
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46       N      - INTEGER.
47              On  entry, N specifies the number of columns of the matrix A.  N
48              must be at least zero.  Unchanged on exit.
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50       ALPHA  - DOUBLE PRECISION.
51              On entry, ALPHA specifies the scalar alpha.  Unchanged on exit.
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53       A      - DOUBLE PRECISION array of DIMENSION ( LDA, n ).
54              Before entry, the leading m by n part of the array A  must  con‐
55              tain the matrix of coefficients.  Unchanged on exit.
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57       LDA    - INTEGER.
58              On  entry, LDA specifies the first dimension of A as declared in
59              the calling (sub) program. LDA must be at least  max(  1,  m  ).
60              Unchanged on exit.
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62       X      - DOUBLE PRECISION array of DIMENSION at least
63              (  1  +  (  n - 1 )*abs( INCX ) ) when TRANS = 'N' or 'n' and at
64              least ( 1 + ( m - 1 )*abs( INCX ) )  otherwise.   Before  entry,
65              the incremented array X must contain the vector x.  Unchanged on
66              exit.
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68       INCX   - INTEGER.
69              On entry, INCX specifies the increment for the  elements  of  X.
70              INCX must not be zero.  Unchanged on exit.
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72       BETA   - DOUBLE PRECISION.
73              On  entry, BETA specifies the scalar beta. When BETA is supplied
74              as zero then Y need not be set on input.  Unchanged on exit.
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76       Y      - DOUBLE PRECISION array of DIMENSION at least
77              ( 1 + ( m - 1 )*abs( INCY ) ) when TRANS = 'N'  or  'n'  and  at
78              least  (  1  +  ( n - 1 )*abs( INCY ) ) otherwise.  Before entry
79              with BETA non-zero, the incremented array  Y  must  contain  the
80              vector y. On exit, Y is overwritten by the updated vector y.
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82       INCY   - INTEGER.
83              On  entry,  INCY  specifies the increment for the elements of Y.
84              INCY must not be zero.  Unchanged on exit.
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86              Level 2 Blas routine.
87
88              -- Written on 22-October-1986.  Jack Dongarra, Argonne  National
89              Lab.   Jeremy Du Croz, Nag Central Office.  Sven Hammarling, Nag
90              Central Office.  Richard Hanson, Sandia National Labs.
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94BLAS routine                     November 2006                        DGEMV(1)