You should edit src/Lib.hs

We've added a basic test suite so you can check the performance of your parallelized mandelbrot set. This should make it easier to check your implementation and make sure its run in parallel. I've also updated the parallelism so that it defaults to running on as many cores as you have, which might make the effects a bit more obvious. A couple notes:

You can run the default suite as follows

stack test

If you want to only test your parallel version, you can run

stack test --test-arguments "-m prefix runMandelPar"

which can be useful once you know how long runMandelSeq takes, as the time won't change between runs.

Similarly, if wanted, you can do the same with runMandelSeq as the prefix to only profile runMandelSeq.

As we've added Handle to the signatures, you can now run these for testing output to the console by passing stdout (which is in System.IO) to these functions.

So, something that might not have been entirely clear is that a .ppm file is a type of image. On macOS, there's default support for viewing these with Preview. On Linux, I'd recommend feh on X11 or imv on Wayland, though most things should support ppms. On Windows, however, tragically the default image viewer doesn't support ppms, to that end I'd recommend this online viewer, which also has pretty nice errors for smaller mistakes. I've also heard Photoshop can open them, though I haven't tested this myself.

Most of the stuff in Lib.hs is the same, but there are a few changes I'll highlight. We've changed runMandelSeq to take an n parameter and be pure instead of an IO action, closer to how runMandelPar works. The n parameter allows us to pass it to writeMandel, which is a slightly changed version of writeMandelPar which allows for running either the sequential or the parallel version. These changes serve to make it easier to test.

As far as methods you're implementing go, we've changed the type signature on a few of them.

runMandelPar :: Int -> [[Int]]

This is a pretty small change, and should allow you to avoid the use of fromIntegral a bit more than previously.

We've added a parameter to jose'sDVDEmporium indicating the number of drivers, as well as handles for in/out IO.

jose'sDVDEmporium :: Int -> Handle -> -> Handle -> IO ()

For a couple of the other part 2 functions, we've added Handle in (deliver, takeOrders). This is so we can pass in either stdout or stdin`, or something else for the sake of testing.

We've also swapped TVar Bool to TMVar () on deliver, as TVar Bool was insufficient for synchronization and would thus result in jumbled output. TMVar () is pretty much like an MVar () and you can treat it as such.

So to move your stuff, you just need to copy paste your methods for the most part. The only differences being in your runMandelPar and some of the part 2 functions. runMandelPar, you should have to change very little anyways.