[R] odesolve/lsoda differences on Windows and Mac

[Setzer.Woodrow@epamail.epa.gov]

I've been talking offline with Hank Stephens about this; note that in
the example he quotes, he set hmin  = 0.1, and the quoted error message
says that the stepsize had reached hmin with no convergence.  I believe
that he intended to set hmax (because of the pulsed input).  Then, Peter
Dalgaard's explanation would make sense -- the PPC platform just needs a
smaller stepsize than does the PC to achieve convergence.

R. Woodrow Setzer, Jr.
National Center for Computational Toxicology
US Environmental Protection Agency
Mail Drop B305-03/US EPA/RTP, NC 27711
Ph: (919) 541-0128    Fax: (919) 541-4284


                                                                        
             "Martin Henry H.                                           
             Stevens"                                                   
             <HStevens at MUOhio                                        To 
             .edu>                    "'R-Help'"                        
                                      <r-help at stat.math.ethz.ch>        
             07/27/2005 12:36                                        cc 
             PM                       Thomas Petzoldt                   
                                      <petzoldt at rcs.urz.tu-dresden.de>, 
                                      Woodrow Setzer/RTP/USEPA/US at EPA   
                                                                Subject 
                                      odesolve/lsoda differences on     
                                      Windows and Mac                   
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        




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.

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



Dr. Martin Henry H. Stevens, Assistant Professor
338 Pearson Hall
Botany Department
Miami University
Oxford, OH 45056

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