Re: NONMEM ODE solver

Mark, The Adams and Gear methods are different methods. The ODEPACK implementation can switch between these two algorithms. But whether or not NONMEM uses this feature is unclear. The switching is controlled by an argument to the ODEPACK solver and I have not been able to follow the NONMEM code (surprise, surprise). Nick Mark Sale - Next Level Solutions wrote: > > Benjamin, > According the comments in the code in version VI (imagine that - > comments in code) > ADVAN6 (DVERK1.for) is originally from IMSL, and is RUNGE KUTTA-VERNER > FIFTH AND SIXTH ORDER METHOD. > ADVAN8, (DGEAR1.for) is VARIABLE ORDER ADAMS PREDICTOR CORRECTOR METHOD > OR GEARS METHOD > and > ADVAN9 is: the Livermore solver, from the ODEPACK. > and, no, I'm pretty sure there is no switching between algorithms. (does > any software do this??) > > BTW, no one ever answered my question from 2 years ago. > > Mark Sale > Next Level Solutions, LLC > www.NextLevelSolns.com > > > -------- Original Message -------- > > Subject: [NMusers] NONMEM ODE solver > > From: Benjamin Ribba <[EMAIL PROTECTED]> > > Date: Sun, May 27, 2007 12:53 pm > > To: <[email protected]> > > > > Dear NMusers, > > > > 1. I have some difficulties to find information on the ODE solver > > implemented in NONMEM. > > Can anyone tell me about the numerical integrator(s) implemented when > > using > > ADVAN6 (recommended for non-stiff) and ADVAN8 (stiff problems)? In > > particular, is the integrator able to switch automatically between > > stiff and > > non-stiff resolution techniques? > > > > 2. Then, still related to the ODE solver, I was also interested in a > > message > > I¹ve picked up from the archive (from Mark Sale, posted January 2005, > > see > > below), for which I couldn¹t find any answer from the group. Additional > > information on these items would be greatly appreciated. > > _______________________________________________________ > > > > From: [EMAIL PROTECTED] > > 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 > > _______________________________________________________ > > > > > > Thanks for your help in this matter. > > > > Benjamin Ribba > > > > Therapeutic Targeting in Oncology (EA3738) > > University Claude Bernard Lyon 1 > > Faculty of Medicine Lyon-Sud > > 165, chemin du grand revoyet > > 69921 Oullins cedex > > > > Tel: +33 4 26 23 59 57 / +33 6 66 06 15 21 -- Nick Holford, Dept Pharmacology & Clinical Pharmacology University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand email:[EMAIL PROTECTED] tel:+64(9)373-7599x86730 fax:373-7556 http://www.health.auckland.ac.nz/pharmacology/staff/nholford/