I'm writing RadauIIA (for now, fixed order 5 with 3 points) method for ODE BVP (basically, collocation method). In the process, I construct an overall non-linear equation that needs to be solved. It takes "mega-vector" x[j] as an argument. However, internally it is more convenient to reshape it to y[m,i,n] where m is the index of original ODE vector, i is the index of the collocation point on time element (or layer) and n is time element index. Also, some inputs to the method (ODE RHS function and BVP function) expect z[m]-kind vector. So far I chose to pass a @view of the "mega-vector" to them.
The alternatives for reshaping and @view would be: - Use the inline function or a macro that maps the indices between mega-vector and arrays (I've tried it, didn't see any difference in performance or memory allocation, but @code_warntype has less "red" spots) - Copy relevant pieces of mega-vector into preallocated arrays of desired shape. This can also be an alternative for @view. Is there some kind of rule of thumb where which one would be preferable? And are there any high costs associated with @view and reshape?
