This?
There's some interesting trickery in there by the looks of things for eliminating the optimiser nastiness - that's not something I've thought about much I'll take a look.
The technique of using an accumulator to keep the whole system "plugged" is one of the ideas you can use versus the need for global variables, volatile, etc.
I'm clearly going to have to ponder this in some depth. While I've thought about trying to get the maths (statistics) right, I've not really given the nitty gritty of the machine's operation a great deal of thought. Then again, that's the whole point of engaging in discussion on this mailing list!
This comment and code returning from main says a lot:
// This is ultimately responsible for preventing all the test code // from being optimized away. Change this to return 0 and you // unplug the whole test's life support system. return test::live_code != 0;
Indeed, I'd spotted that. It's a nice comment! ;-) -ed