code>       AP is REAL array, dimension at least
        ( ( n*( n + 1 ) )/2 ).
        Before entry with UPLO = &#39;U&#39; or &#39;u&#39;, the array AP must
        contain the upper triangular matrix packed sequentially,
        column by column, so that AP( 1 ) contains a( 1, 1 ),
        AP( 2 ) and AP( 3 ) contain a( 1, 2 ) and a( 2, 2 )
        respectively, and so on.
        Before entry with UPLO = &#39;L&#39; or &#39;l&#39;, the array AP must
        contain the lower triangular matrix packed seq