### Parallel computation for different functions

For a single function with a list of inputs, the @parallel decoration can be used to do parallel computation. I am wandering whether it is possible to do parallel computation for different functions.

A simple is example is to calculate the difference f-g of two independent functions f and g. How can I ask SageMath to simultaneously compute the values of f and g, and then calculate the difference?

My time measurements suggest that when calculating the difference f-g, SageMath actually calculates f and g one after another, and then take the difference.

I can think of a naive approach using the @parallel decoration. I can create a function whose input variable is the name of the functions I want to compute simultaneously. Then I use a list of function names as input to get a generator of outputs. This may work if the final result doesn't depend on the order of the outputs, but does not work if the order matters, for example when taking the difference.

In general, suppose I have a flow chart for the computation, in other words, I already know which jobs can be parallelized and how the information flows to the next stage. Then what is the best way to implement the flow chart?