questions on ODE solver errors

From: mark.e.sale@gsk.com Subject: [NMusers] questions on ODE solver errors Date: Wed, January 26, 2005 4:40 pm If the NOABORT option is used for the ODE solvers, and the ODE solver has "numerical difficulties", giving the message: NUMERICAL DIFFICULTIES WITH INTEGRATION ROUTINE. MAXIMUM NO. OF EVALUATIONS OF DIFFERENTIAL EQUATIONS, 100000, EXCEEDED. 0END OF PRED EXIT CODE MESSAGES FROM THE ESTIMATION STEP But, NONMEM continues to plod along. Does anyone know what NONMEM does instead? I assume that the OBJ contribution for that subject cannot be calculated, so, the gradient for the dimension(s) requiring that OBJ cannot be calculated. Seems like an error to simply ignore the OBJ contribution from that person (resulting in a lower OBJ for that function evaluation, and a bad gradient and Hessian). Is that function evaluation discarded, and no gradient is generated for that dimension/iteration? But I don't see a 0 gradient anywhere in the output (I know, in NONMEM V, it isn't as simple as one function evaluation per dimension (+1)) Thanks Mark Sale M.D. Global Director, Research Modeling and Simulation GlaxoSmithKline 919-483-1808 Mobile 919-522-6668 _______________________________________________________