nd the strictly
          lower triangular part of the array is not referenced.
          On entry, if UPLO = 'L', the leading N-by-N lower
          triangular part of this array must contain the lower
          triangular part of the symmetric matrix X and the strictly
          upper triangular part of the array is not referenced.
          On exit, each diagonal element of this array has half its
          input value, but the other elements are not modified.

  LDX     INTEGER
          The leading dim