Thread Subject: Problem on the ODE45

Hi,
I am trying to solve a system of 2nd order non-linear different equatio=
ns =

by the ODE45 solver, I encounters the following problem. I am not quite =
 =

sure what reason cause this error since I got a very strange output. The=
  =

error message is:

Warning: Failure at t=3D4.294891e+001. Unable to meet integration =

tolerances without reducing the step size below the smallest value allow=
ed =

(1.136868e-013) at time t.

-- =

Using Opera's revolutionary e-mail client: http://www.opera.com/mail/

Wilson wrote:
>
>
> Hi,
> I am trying to solve a system of 2nd order non-linear different
> equations
> by the ODE45 solver, I encounters the following problem. I am not
> quite
> sure what reason cause this error since I got a very strange
> output. The
> error message is:
>
> Warning: Failure at t=4.294891e+001. Unable to meet integration
> tolerances without reducing the step size below the smallest value
> allowed
> (1.136868e-013) at time t.
>
> --
> Using Opera's revolutionary e-mail client: <http://www.opera.com/mail/>
>
  Maybe you can solve the problem by changing the step to be much
smaller.

try a stiff ODE solver

help ode15s

Shaun

Shaun <s@s.com> wrote in message
<ef56931.1@webcrossing.raydaftYaTP>...
> try a stiff ODE solver
>
> help ode15s
>
> Shaun

I was getting the same error message as wilson and I tried
using ode15s instead and I'm still getting. Is there any
other way to fix it?

"Mohamed " <bayoumi2@uiuc.edu> wrote in message
<f9a5ah$o1f$1@fred.mathworks.com>...
> Shaun <s@s.com> wrote in message
> <ef56931.1@webcrossing.raydaftYaTP>...
> > try a stiff ODE solver
> >
> > help ode15s
> >
> > Shaun
>
> I was getting the same error message as wilson and I tried
> using ode15s instead and I'm still getting. Is there any
> other way to fix it?


============================
Hi Mohamed,

Please try this before call ode solver and let us know the
results.

options = odeset('RelTol',1e-3,'AbsTol',1e-3);

Yang

I have the same problem, and I have played around with all
the solver (stiff, nonstiff) and many different values for
absTol and RelTol. I keep getting this warning and the
integration cannot be completed in my time interval. Any
suggestions? I would really appreciate any help!

Antonios


"Yang Zhang" <zhyang99@hotmail.com> wrote in message
<f9ajpn$ea6$1@fred.mathworks.com>...
> "Mohamed " <bayoumi2@uiuc.edu> wrote in message
> <f9a5ah$o1f$1@fred.mathworks.com>...
> > Shaun <s@s.com> wrote in message
> > <ef56931.1@webcrossing.raydaftYaTP>...
> > > try a stiff ODE solver
> > >
> > > help ode15s
> > >
> > > Shaun
> >
> > I was getting the same error message as wilson and I tried
> > using ode15s instead and I'm still getting. Is there any
> > other way to fix it?
>
>
> ============================
> Hi Mohamed,
>
> Please try this before call ode solver and let us know the
> results.
>
> options = odeset('RelTol',1e-3,'AbsTol',1e-3);
>
> Yang
>

Take a look at your equations. If all solvers behave the same, then perhaps
there is a point of singularity and the solver(s) cannot go past it?

-Jacek

 ---------------------------------------

"Antonios " <asangvin@stern.nyu.edu> wrote in message
news:fgirdb$179$1@fred.mathworks.com...
>I have the same problem, and I have played around with all
> the solver (stiff, nonstiff) and many different values for
> absTol and RelTol. I keep getting this warning and the
> integration cannot be completed in my time interval. Any
> suggestions? I would really appreciate any help!
>
> Antonios
>
>
> "Yang Zhang" <zhyang99@hotmail.com> wrote in message
> <f9ajpn$ea6$1@fred.mathworks.com>...
>> "Mohamed " <bayoumi2@uiuc.edu> wrote in message
>> <f9a5ah$o1f$1@fred.mathworks.com>...
>> > Shaun <s@s.com> wrote in message
>> > <ef56931.1@webcrossing.raydaftYaTP>...
>> > > try a stiff ODE solver
>> > >
>> > > help ode15s
>> > >
>> > > Shaun
>> >
>> > I was getting the same error message as wilson and I tried
>> > using ode15s instead and I'm still getting. Is there any
>> > other way to fix it?
>>
>>
>> ============================
>> Hi Mohamed,
>>
>> Please try this before call ode solver and let us know the
>> results.
>>
>> options = odeset('RelTol',1e-3,'AbsTol',1e-3);
>>
>> Yang
>>
>

I think the solution of your equation may have an asymptote
at t=3D4.294891e+001. That's why the computation stops at
that time.

Wilson <ykip5@ie.cuhk.edu.hk> wrote in message
<op.tr5qufbgxsy48p@mtcpc008.plab.ie.cuhk.edu.hk>...
> Hi,
> I am trying to solve a system of 2nd order non-
linear different equatio=
> ns =
>
> by the ODE45 solver, I encounters the following problem.
I am not quite =
> =
>
> sure what reason cause this error since I got a very
strange output. The=
> =
>
> error message is:
>
> Warning: Failure at t=3D4.294891e+001. Unable to meet
integration =
>
> tolerances without reducing the step size below the
smallest value allow=
> ed =
>
> (1.136868e-013) at time t.
>
> -- =
>
> Using Opera's revolutionary e-mail client:
http://www.opera.com/mail/