Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2004
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2004

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Garbage collection problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg51852] Re: Garbage collection problem
  • From: sean_incali at yahoo.com (sean kim)
  • Date: Wed, 3 Nov 2004 01:26:03 -0500 (EST)
  • References: <cm7d0u$lho$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

flank the routine in Module[] and keep things local. 

In[13]:=
(* Setup *) 

run[do_]:=Do[
    Module[{}, 
      eq={9.8*(0.99*Cos[qS[t]] + 0.01*Cos[qH[t] + qS[t]]) - 
              0.01*Sin[qH[t]]*qH'[t]*qS'[t] - 
              0.01*Sin[qH[t]]* 
                qH'[t]*(qH'[t] + qS'[t]) + (0.001 + 0.01*Cos[qH[t]])* 
                qH''[t] + (0.982 + 0.02*Cos[qH[t]])*qS''[t] == 0, 
          0.1*Cos[qH[t] + qS[t]] + 0.01*Sin[qH[t]]*qS'[t]^2 + 
              0.001*qH''[t] + (0.001 + 0.01*Cos[qH[t]])*qS''[t] == 0, 
          qS[0] == 1.71, qS'[0] == -1.01, qH[0] == 2.84, qH'[0] == 1.1}; 
      vars={qS[t], qH[t], qS'[t], qH'[t]}; 
      test=qH[t] >= Pi && 
            2*Cos[qH[t]/2]*Cos[qH[t]/2 + qS[t]]*Sin[Pi/180] + 
                Cos[Pi/180]*(Cos[qS[t]]*Sin[qH[t]] + (1 + Cos[qH[t]])* 
                        Sin[qS[t]]) < -0.01 && 
            Cos[qH[t] + qS[t]]* 
                  Derivative[1][qH][t] + (Cos[qS[t]] + Cos[qH[t] + qS[t]])* 
                  Derivative[1][qS][t] < -0.01 || Abs[qH[t]] < Pi/6 || 
          Sin[qS[t]] < 1/4; $HistoryLength=0; ],
    {do}]
(* end *) 

In[20]:=
run[2000]; 
MemoryInUse[] 

Out[21]=
2944448

In[24]:=
run[2]; 
MemoryInUse[] 

Out[25]=
2944448


D Herring <dherring at at.uiuc.dot.edu> wrote in message news:<cm7d0u$lho$1 at smc.vnet.net>...
> To anyone who can help me,
> 
> I've written a small simulator to model the system I'm studying.  It 
> works nicely.  Now I'm wrapping that simulator in a set of Do[] loops to 
> generate maps of its behavior.  Unfortunately, long runs quickly fill my 
> 512MB of RAM, even when dumping all my data to files as it is generated.
> 
> After a good bit of debugging, I have isolated (at least half of of) the 
> memory problem to my use of a StoppingTest inside NDSolve.
> 
> Example:
> (* Setup *)
> eq={9.8*(0.99*Cos[qS[t]] + 0.01*Cos[qH[t] + qS[t]]) -
>            0.01*Sin[qH[t]]*qH'[t]*qS'[t] -
>            0.01*Sin[qH[t]]*
>              qH'[t]*(qH'[t] + qS'[t]) + (0.001 + 0.01*Cos[qH[t]])*
>              qH''[t] + (0.982 + 0.02*Cos[qH[t]])*qS''[t] == 0,
>        0.1*Cos[qH[t] + qS[t]] + 0.01*Sin[qH[t]]*qS'[t]^2 +
>            0.001*qH''[t] + (0.001 + 0.01*Cos[qH[t]])*qS''[t] == 0,
>        qS[0] == 1.71,
>        qS'[0] == -1.01,
>         qH[0] == 2.84,
>        qH'[0] == 1.1};
> vars={qS[t], qH[t], qS'[t], qH'[t]};
> test=qH[t] >= Pi &&
>          2*Cos[qH[t]/2]*Cos[qH[t]/2 + qS[t]]*Sin[Pi/180] +
>              Cos[Pi/180]*(Cos[qS[t]]*Sin[qH[t]] + (1 + Cos[qH[t]])*
>                      Sin[qS[t]]) < -0.01 &&
>          Cos[qH[t] + qS[t]]*
>                Derivative[1][qH][t] + (Cos[qS[t]] + Cos[qH[t] + qS[t]])*
>                Derivative[1][qS][t] < -0.01 || Abs[qH[t]] < Pi/6 ||
>        Sin[qS[t]] < 1/4;
> $HistoryLength=0;
> (* end *)
> 
> (* example a *)
> Do[
>      soln=NDSolve[eq,vars,{t,0,2}][[1]];
>      ,
>      {20}];
> MemoryInUse[]
> (* end *)
> 
> (* example b *)
> Do[
>      soln=NDSolve[eq,vars,{t,0,2},StoppingTest->test][[1]];
>      ,
>      {20}];
> MemoryInUse[]
> (* end *)
> 
> To reproduce this, start a fresh kernel.  Execute the setup code, and 
> then repeatedly run example a or b.  When I repeatedly run example a, 
> MemoryInUse[] quickly converges to a constant value, as expected. 
> However, each run of example b results in an increase in memory 
> consumption.  Why?  How can I fix/avoid this behavior?  I stripped out 
> some other logic, but all I really want are a few numbers from the last 
> several "soln"s of each run, to observe convergence properties.
> 
> FWIW, I'm running on $Version=5.0 for Linux (November 18, 2003)
> 
> Thanks,
> Daniel


  • Prev by Date: Re: Re: closing notebook cells
  • Next by Date: Re: bimodal distribution in sign of difference of Pi digits]
  • Previous by thread: Re: Re: Garbage collection problem
  • Next by thread: Re: Garbage collection problem