Re: How to pass initial conditions to IDA methods via NDSolve?
- To: mathgroup at smc.vnet.net
- Subject: [mg121841] Re: How to pass initial conditions to IDA methods via NDSolve?
- From: Oliver Ruebenkoenig <ruebenko at wolfram.com>
- Date: Wed, 5 Oct 2011 03:57:51 -0400 (EDT)
- Delivered-to: email@example.com
Hi, On Tue, 4 Oct 2011, GRW wrote: > New to Mathematica so this might be gibberish. Without seeing the equations this is hard to answer. What follows are some random ideas. > > I'm trying to integrate numerically a PDE system. NDSolve complains > saying this: > > "NDSolve::icfail: Unable to find initial conditions that satisfy the > residual function within specified tolerances. Try giving initial > conditions for both values and derivatives of the functions." > > Now I've figured out how to get numerical estimates for some of the > derivatives in my PDE system (using FindRoot there). > However, if I add these conditions to my preexisting list of initial > conditions and boundary conditions, Mathematica complains that there > are too many boundary and/or initial conditions: > - Try lowering AccuracyGoal/PrecisionGoal - Can you use exact values for your equations? > "NDSolve::ivone: Boundary values may only be specified for one > independent variable. Initial values may only be specified at one > value of the other independent variable" > In the time integration method option, try giving "Timevariable" -> t > It seems as if IDA was selected automatically as "Method" option of > NDSolve and IDA does not seem to allow for initial conditions passed > to it. There is information about the IDA here: tutorial/NDSolveIDAMethod Hope this gets you started. Oliver > > I've tried using Method option "Shooting" (because this one seems to > allow for initial conditions passed), however NDSolve isn't too fond > of that one either: > "NDSolve::nodae: The method NDSolve`Shooting is not currently > implemented to solve differential-algebraic equations. Use Method -> > Automatic instead." > > > Any advice greatly appreciated! > >