Something I just noticed that may either complicate using multiple cores in parallel, or obviate the need to do anything special to take advantage of it: different machines use the multiple cores differently.
I had assumed, based on what I'd seen on some (older) dual-core machines, that starting a single CPU-intensive process makes full use of a single core while leaving the other one relatively idle, as shown here.
We see that the left core is at maximum usage whereas the right one is relatively idle.
However, running this same CPU-intensive task on another (newer) machine gave this profile.
Here we see both cores working at about 50% capacity at the same time - a completely different dynamic than that of the other machine.