1SSPMV(1)                         BLAS routine                         SSPMV(1)
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NAME

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

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

20       SSPMV  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, supplied in packed form.
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ARGUMENTS

27       UPLO   - CHARACTER*1.
28              On entry, UPLO specifies whether the upper or  lower  triangular
29              part  of the matrix A is supplied in the packed array AP as fol‐
30              lows:
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32              UPLO = 'U' or 'u'   The upper triangular part of A  is  supplied
33              in AP.
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35              UPLO  =  'L' or 'l'   The lower triangular part of A is supplied
36              in AP.
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38              Unchanged on exit.
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40       N      - INTEGER.
41              On entry, N specifies the order of the matrix A.  N must  be  at
42              least zero.  Unchanged on exit.
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44       ALPHA  - REAL            .
45              On entry, ALPHA specifies the scalar alpha.  Unchanged on exit.
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47       AP     - REAL             array of DIMENSION at least
48              ( ( n*( n + 1 ) )/2 ).  Before entry with UPLO = 'U' or 'u', the
49              array AP must contain the upper triangular part of the symmetric
50              matrix  packed  sequentially,  column by column, so that AP( 1 )
51              contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 1, 2 ) and a(
52              2, 2 ) respectively, and so on.  Before entry with UPLO = 'L' or
53              'l', the array AP must contain the lower triangular part of  the
54              symmetric  matrix packed sequentially, column by column, so that
55              AP( 1 ) contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 2,  1
56              ) and a( 3, 1 ) respectively, and so on.  Unchanged on exit.
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58       X      - REAL             array of dimension at least
59              (  1  +  ( n - 1 )*abs( INCX ) ).  Before entry, the incremented
60              array X must contain the n element vector x.  Unchanged on exit.
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62       INCX   - INTEGER.
63              On entry, INCX specifies the increment for the  elements  of  X.
64              INCX must not be zero.  Unchanged on exit.
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66       BETA   - REAL            .
67              On  entry, BETA specifies the scalar beta. When BETA is supplied
68              as zero then Y need not be set on input.  Unchanged on exit.
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70       Y      - REAL             array of dimension at least
71              ( 1 + ( n - 1 )*abs( INCY ) ).  Before  entry,  the  incremented
72              array Y must contain the n element vector y. On exit, Y is over‐
73              written by the updated vector y.
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75       INCY   - INTEGER.
76              On entry, INCY specifies the increment for the  elements  of  Y.
77              INCY must not be zero.  Unchanged on exit.
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FURTHER DETAILS

80       Level 2 Blas routine.
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82       -- Written on 22-October-1986.
83          Jack Dongarra, Argonne National Lab.
84          Jeremy Du Croz, Nag Central Office.
85          Sven Hammarling, Nag Central Office.
86          Richard Hanson, Sandia National Labs.
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91BLAS routine                     November 2008                        SSPMV(1)