1SSYMV(1)                         BLAS routine                         SSYMV(1)
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NAME

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

9       SUBROUTINE SSYMV(UPLO,N,ALPHA,A,LDA,X,INCX,BETA,Y,INCY)
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11           REAL                                                ALPHA,BETA
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13           INTEGER                                             INCX,INCY,LDA,N
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15           CHARACTER                                           UPLO
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17           REAL                                                A(LDA,*),X(*),Y(*)
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PURPOSE

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

27       UPLO   - CHARACTER*1.
28              On  entry,  UPLO specifies whether the upper or lower triangular
29              part of the array A is to be referenced as follows:
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31              UPLO = 'U' or 'u'   Only the upper triangular part of A is to be
32              referenced.
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34              UPLO = 'L' or 'l'   Only the lower triangular part of A is to be
35              referenced.
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37              Unchanged on exit.
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39       N      - INTEGER.
40              On entry, N specifies the order of the matrix A.  N must  be  at
41              least zero.  Unchanged on exit.
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43       ALPHA  - REAL            .
44              On entry, ALPHA specifies the scalar alpha.  Unchanged on exit.
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46       A      - REAL             array of DIMENSION ( LDA, n ).
47              Before  entry  with  UPLO = 'U' or 'u', the leading n by n upper
48              triangular part of the array A must contain the upper triangular
49              part  of  the symmetric matrix and the strictly lower triangular
50              part of A is not referenced.  Before entry with UPLO  =  'L'  or
51              'l',  the  leading  n  by n lower triangular part of the array A
52              must contain the lower triangular part of the  symmetric  matrix
53              and  the  strictly upper triangular part of A is not referenced.
54              Unchanged on exit.
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56       LDA    - INTEGER.
57              On entry, LDA specifies the first dimension of A as declared  in
58              the  calling  (sub)  program.  LDA must be at least max( 1, n ).
59              Unchanged on exit.
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61       X      - REAL             array of dimension at least
62              ( 1 + ( n - 1 )*abs( INCX ) ).  Before  entry,  the  incremented
63              array X must contain the n element vector x.  Unchanged on exit.
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65       INCX   - INTEGER.
66              On  entry,  INCX  specifies the increment for the elements of X.
67              INCX must not be zero.  Unchanged on exit.
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69       BETA   - REAL            .
70              On entry, BETA specifies the scalar beta. When BETA is  supplied
71              as zero then Y need not be set on input.  Unchanged on exit.
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73       Y      - REAL             array of dimension at least
74              (  1  +  ( n - 1 )*abs( INCY ) ).  Before entry, the incremented
75              array Y must contain the n element vector y. On exit, Y is over‐
76              written by the updated vector y.
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78       INCY   - INTEGER.
79              On  entry,  INCY  specifies the increment for the elements of Y.
80              INCY must not be zero.  Unchanged on exit.
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FURTHER DETAILS

83       Level 2 Blas routine.
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85       -- Written on 22-October-1986.
86          Jack Dongarra, Argonne National Lab.
87          Jeremy Du Croz, Nag Central Office.
88          Sven Hammarling, Nag Central Office.
89          Richard Hanson, Sandia National Labs.
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94BLAS routine                     November 2008                        SSYMV(1)