[R] odesolve/lsoda differences on Windows and Mac

[Peter Dalgaard]

"Martin Henry H. Stevens" <HStevens at 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

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   O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
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