Is parallel programming hard, and, if so, what can you do about it?

The majority of tasks are "embarrassingly parallel" as they say. Which is just to mean, there are a lot of standalone tasks that need to be done. For example, any web server is embarrassingly parallel. You don't need to be clever, you just need to have the processing power available to handle them.

You're much better off just picking a paradigm and sticking with it. I'd say it doesn't matter which one, but there are a few paradigms that are clear winners in my experience: immutability always wins, and Erlang-style messaging seems to work very easily. If you have the opportunity to determine the architecture of a parallel project, most languages can imitate Erlang-style parallelism with builtin libraries. But what I will say is that which paradigm you pick doesn't matter so much that you should switch paradigms mid-project.

A word of caution: concurrency and parallelism are not the same thing. Cooperative multithreading is a way of gaining some of the benefits of parallelism in a single process. If you come from an environment where this is the norm (read: JavaScript) it's quite possible that you've never written a line of parallel code. If you try to apply the same paradigms from this sort of environment to parallel programming, they will not work.

The main issue I found was the language and libraries are really hard to pick up as a beginner. A library for ruby or python would start off with a few examples showing how the most common use case works and then full api docs for the library. Haskell libraries usually only provide a function name and type definition and if you are lucky you get a one liner telling you what the function does but not how to use it.

This seems to be not an issue for haskell experts because "PathMultiPiece ps => (ps -> Writer LiteApp ()) -> Writer LiteApp ()" is all the info needed but I found it much harder to use because of that.

I also found that many of the libraries were totally inaccessible unless you had an understanding abstract mathematical constructs. I wanted to do some basic xml parsing in haskell and the prerequisite was reading some huge book on the theory of some math behind how the library works. I then switched to ruby and nokogiri had on the website basically the exact code snipit I needed.