NDSolve and numeric-only computation
- To: mathgroup at smc.vnet.net
- Subject: [mg21848] NDSolve and numeric-only computation
- From: bumi314 at aol.com (Carl Bumiller)
- Date: Sun, 30 Jan 2000 18:53:30 -0500 (EST)
- Organization: AOL http://www.aol.com
- Sender: owner-wri-mathgroup at wolfram.com
I have a question about NDSolve and numeric-only computation.
First I have defined RHS=Compile[{{x,_Real}},........] where ........
is some complicated expression, then I ran
NDSolve[{x'[t]==RHS[x[t]],x[0]==1},{x},{t,0,1}]
and got the error message
CompiledFunction::cfr:
Cannot use compiled code; Argument x[t] at position 1
should be a machine-size real number.
This suggests that NDSolve is trying to solve symbolically rather than
numerically. How do I get NDSolve to evaluate RHS numerically rather
than symbolically?? When I try Compiled->True or Compiled->False
with NDSolve, I get the same error message. Since RHS is complicated,
its symbolic evaluation is time comsuming although the equation is
eventually solved. I am running Mathematica 3.0 for Digital Unix.
Carl Bumiller
bumi314 at aol.com