Re: [R] odesolve/lsoda differences on Windows and Mac

From: Peter Dalgaard <p.dalgaard_at_biostat.ku.dk>
Date: Thu 28 Jul 2005 - 06:51:30 EST

"Martin Henry H. Stevens" <HStevens@muohio.edu> writes:

> Hi -
> I am getting different results when I run the numerical integrator
> function lsoda (odesolve package) on a Mac and a PC. I am trying to
> simulating a system of 10 ODE's with two exogenous pulsed inputs to the
> system, and have had reasonably good success with many model parameter
> sets. Under some parameter sets, however, the simulations fail on the
> Mac (see error message below). The same parameter sets, however, appear
> to run fine for our computational technician on his PC, generating
> apparently very reasonable data.

One thought: Integrating across input pulses is a known source of "turbulence" in lsoda. You might have better luck integrating over intervals in which the input function is continuous.

Tweaking the lsoda tolerances is another thing to try.

I haven't seen lsoda fail like that, but it's not too surprising that marginal cases show platform dependency (i.e. the integrator just fails on Mac and barely succeeds on PC).  

> Our tech is successfully running
> Dell Latitude D810, Windows XP Pro (Service Pack 2), 1Gb
> RAM. RGUI 2.1.1
>
> I am running:
> R Version 2.1.1 (2005-06-20) on a
> Mac OS 10.3.9
> Machine Model: Power Mac G5
> CPU Type: PowerPC 970 (2.2)
> Number Of CPUs: 2
> CPU Speed: 2 GHz
> L2 Cache (per CPU): 512 KB
> Memory: 1.5 GB
> Bus Speed: 1 GHz
> Boot ROM Version: 5.0.7f0
> Serial Number: XB3472Q1NVS
>
> My Error Message
> > system.time(
> + outAc2 <- as.data.frame(lsoda(xstart,times, pondamph, parms,
> tcrit=170*730, hmin=.1))
> + )
> [1] 0.02 0.01 0.04 0.00 0.00
> Warning messages:
> 1: lsoda-- at t (=r1) and step size h (=r2), the
> 2: corrector convergence failed repeatedly
> 3: or with abs(h) = hmin
> 4: Returning early from lsoda. Results are accurate, as far as they go
>
> Thanks for any input.
>
> Hank Stevens

-- 
   O__  ---- Peter Dalgaard             ุster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)                  FAX: (+45) 35327907

______________________________________________
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Received on Thu Jul 28 06:54:47 2005

This archive was generated by hypermail 2.1.8 : Fri 03 Mar 2006 - 03:34:06 EST