Parallelize symbolic operations

[jkosata]

A macro @maybethread is ready for this, but some parts of SymbolicUtils.jl are currently not threadsafe.

Typical bottlenecks:

• fourier_term when getting the harmonic equations
• get_Jacobian for the symbolic Jacobian

[oameye]

@jkosata Do you think we can make progress on this issue?
For example, the for loop in fourier_term can be threaded if the variables number of harmonic variables is higher than 2.

I suppose you want to define the macro from this discourse question:

macro maybethread(loop)
  if use_threads
    quote Threads.@threads $(Expr(loop.head,
                             Expr(loop.args[1].head, esc.(loop.args[1].args)...),
                             esc(loop.args[2]))); end
  else
    # @warn "running single threaded"
    quote $(esc(loop)); end
  end
end

[jkosata]

Such a macro is already defined, the problem is that some SymbolicUtils.jl functions are not threadsafe , see JuliaSymbolics/SymbolicUtils.jl#408