Thanks! I've already partly rewritten it in C once, but I misunderstood the access pattern and I ended up having a lot of cache misses. The speedup was measur

Thanks! I've already partly rewritten it in C once, but I misunderstood the access pattern and I ended up having a lot of cache misses. The speedup was measurable, but disappointing, and the prospect of doing another rewrite had put me off. I hadn't put two and two together about this being an effective way to share memory under multiprocessing until reading this thread, so it's worth revisiting now.