I would like to ask you that whether you have already had experience on coding synthesizable code for FPGAs or ASICs?
If you have read the documentation on MyHDL website, you should know that MyHDL does not turn arbitrary Python into silicon. As programming in other HDLs, you should have a clear mind of digital circuits you would make. MyHDL would be more friendly than VHDL, but you should still take the circuits in mind. That is to say, you should code as "synthesizable" Python code.
By the way, in my limited experience of signal processing, I have never heard of someone implemented an ODE solver directly on silicon. If the ODEs are simple enough, would you please solve it by hand first?