P( 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 sequentially,
        column by column, so that AP( 1 ) contains a( 1, 1 ),
        AP( 2 ) and AP( 3 ) contain a( 2, 1 ) and a( 3, 1 )
        respectively, and so on.
        Note that when DIAG = &#39;U&#39; or &#39;u&#39;, the diagonal elements of
        A are not referenced, but are assumed to be unity.