Initial conditions don’t cause a recompile. It’s just the first time you solve with a method in a new Julia session. You can change initial conditions, parameters, etc (run a parameter estimation). The only thing that matters is that every time a new code is generated (new types are used), then you have to recompile.
And the issue was that the view was allocating for some reason. Usually Julia’s compiler catches this and optimizes it away. I’m not sure why it wasn’t in this case 
. But yeah, at the end of the day Julia will get to the speed of compiled code if you write it to be like the compiled code, which isn’t always the nicest form. I will say that Fortran does look pretty high level for being a compiled language, so it is a fun one to code in.
Yes, only the pure-Julia methods can use static arrays.
BTW, it looks like you’re doing Verner robust and efficient? How’re you seeing the robust ones doing? I did a bunch of tests with a tableau-based implementation awhile back but never did too many benchmarks after optimizing everything else. I’ve wanted to revisit them.