       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:=
(* 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 == 1.71, qS' == -1.01, qH == 2.84, qH' == 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[qH][t] + (Cos[qS[t]] + Cos[qH[t] + qS[t]])*
Derivative[qS][t] < -0.01 || Abs[qH[t]] < Pi/6 ||
Sin[qS[t]] < 1/4; \$HistoryLength=0; ],
{do}]
(* end *)

In:=
run;
MemoryInUse[]

Out=
2944448

In:=
run;
MemoryInUse[]

Out=
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 == 1.71,
>        qS' == -1.01,
>         qH == 2.84,
>        qH' == 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[qH][t] + (Cos[qS[t]] + Cos[qH[t] + qS[t]])*
>                Derivative[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}][];
>      ,
>      {20}];
> MemoryInUse[]
> (* end *)
>
> (* example b *)
> Do[
>      soln=NDSolve[eq,vars,{t,0,2},StoppingTest->test][];
>      ,
>      {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

```

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