1DSYMV(1)                         BLAS routine                         DSYMV(1)
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NAME

6       DSYMV - performs the matrix-vector operation   y := alpha*A*x + beta*y,
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SYNOPSIS

9       SUBROUTINE DSYMV(UPLO,N,ALPHA,A,LDA,X,INCX,BETA,Y,INCY)
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11           DOUBLE                                              PRECISION
12                                                               ALPHA,BETA
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14           INTEGER                                             INCX,INCY,LDA,N
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16           CHARACTER                                           UPLO
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18           DOUBLE                                              PRECISION
19                                                               A(LDA,*),X(*),Y(*)
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PURPOSE

22       DSYMV  performs the matrix-vector  operation
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24       where alpha and beta are scalars, x and y are n element vectors  and  A
25       is an n by n symmetric matrix.
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ARGUMENTS

29       UPLO   - CHARACTER*1.
30              On  entry,  UPLO specifies whether the upper or lower triangular
31              part of the array A is to be referenced as follows:
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33              UPLO = 'U' or 'u'   Only the upper triangular part of A is to be
34              referenced.
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36              UPLO = 'L' or 'l'   Only the lower triangular part of A is to be
37              referenced.
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39              Unchanged on exit.
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41       N      - INTEGER.
42              On entry, N specifies the order of the matrix A.  N must  be  at
43              least zero.  Unchanged on exit.
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45       ALPHA  - DOUBLE PRECISION.
46              On entry, ALPHA specifies the scalar alpha.  Unchanged on exit.
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48       A      - DOUBLE PRECISION array of DIMENSION ( LDA, n ).
49              Before  entry  with  UPLO = 'U' or 'u', the leading n by n upper
50              triangular part of the array A must contain the upper triangular
51              part  of  the symmetric matrix and the strictly lower triangular
52              part of A is not referenced.  Before entry with UPLO  =  'L'  or
53              'l',  the  leading  n  by n lower triangular part of the array A
54              must contain the lower triangular part of the  symmetric  matrix
55              and  the  strictly upper triangular part of A is not referenced.
56              Unchanged on exit.
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58       LDA    - INTEGER.
59              On entry, LDA specifies the first dimension of A as declared  in
60              the  calling  (sub)  program.  LDA must be at least max( 1, n ).
61              Unchanged on exit.
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63       X      - DOUBLE PRECISION array of dimension at least
64              ( 1 + ( n - 1 )*abs( INCX ) ).  Before  entry,  the  incremented
65              array X must contain the n element vector x.  Unchanged on exit.
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67       INCX   - INTEGER.
68              On  entry,  INCX  specifies the increment for the elements of X.
69              INCX must not be zero.  Unchanged on exit.
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71       BETA   - DOUBLE PRECISION.
72              On entry, BETA specifies the scalar beta. When BETA is  supplied
73              as zero then Y need not be set on input.  Unchanged on exit.
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75       Y      - DOUBLE PRECISION array of dimension at least
76              (  1  +  ( n - 1 )*abs( INCY ) ).  Before entry, the incremented
77              array Y must contain the n element vector y. On exit, Y is over‐
78              written by the updated vector y.
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80       INCY   - INTEGER.
81              On  entry,  INCY  specifies the increment for the elements of Y.
82              INCY must not be zero.  Unchanged on exit.
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FURTHER DETAILS

85       Level 2 Blas routine.
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87       -- Written on 22-October-1986.
88          Jack Dongarra, Argonne National Lab.
89          Jeremy Du Croz, Nag Central Office.
90          Sven Hammarling, Nag Central Office.
91          Richard Hanson, Sandia National Labs.
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96BLAS routine                     November 2008                        DSYMV(1)