I think the question is whether the Hessian wrt the RE's is sparse enough to make anaysis with the SEPARABLE_FUNCTION and the -sparse option worthwhile. I suspect is will not be but who knows without a bit of thought. -- David A. Fournier P.O. Box 2040, Sidney, B.C. V8l 3S3 Canada Phone/FAX 250-655-3364 http://otter-rsch.com