It is the last official submission this year:
I am not releasing any source code this year, but for those curious how much LSTM costs, here is a version without LSTM:
It could qualify for the prize if the size of executable was smaller.
~1.4% bigger compressed size, but speed is about twice higher. Or is it more like 2.5 times higher on your machine?
Perhaps decompression time can be below 1.5 hours on modern computers. And it's for a single-threaded application.