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