Number of evaluations of differential equations

From: phil.lowe@pharma.Novartis.com Subject: Number of evaluations of differential equations Date: Mon, 7 Aug 2000 11:00:07 +0000 Dear NM-users, I am using NM for running simulations of PKPD models written with differential equations. It is often quicker to use NM rather than the other PK software I have, especially when running many scenarios to do a sensitivity analysis. It is also useful to have the model written in NM as a precursor to adding error functions later on. However, I often encounter the error message NUMERICAL DIFFICULTIES WITH INTEGRATION ROUTINE. MAXIMUM NO. OF EVALUATIONS OF DIFFERENTIAL EQUATIONS, 100000, EXCEEDED as it hits the 100000 limit for integrating the differential between timepoints. I have to use ADVAN8 or 9 as the differential equations I use are stiff, there being some very sharp changes in slope in the PD function. I have included the verbatim code (from http://huxley.phor.com/nonmem/nm/98oct071998.html): "FIRST " COMMON /PRCOMG/ IDUM1,IDUM2,IMAX,IDUM4,IDUM5 " INTEGER IDUM1,IDUM2,IMAX,IDUM4,IDUM5 " IMAX=1000000 in the $PK block, which partially solves the problem, but then the routine fails at the $TABLE step. I assume the procedure at that point calls a subroutine which has the original 100000 limit. My question is, can I alter the limit for the number of evaluations of the differential equations? If so, which Fortran subroutines need to be edited? Best regards, Phil Lowe ________________________________________________ Dr Philip Lowe Novartis Horsham Research Centre Horsham RH12 5AB UK tel. +44 1403 323696 from 1st September 2000 Novartis Pharmaceuticals AG Drug Metabolism and Pharmacokinetics CH-4002 Basel Switzerland tel. +41 61 696 7335