Quote from: kjj on May 08, 2012, 05:38:20 PM

Quote from: Meni Rosenfeld on May 08, 2012, 10:06:11 AM

Quote from: kjj on May 08, 2012, 06:42:22 AM

"Right shift by 1 bit" is not the same operation as "divide by two and round down". They obtain the same result if done properly, but have different meta costs, as you helped me demonstrate.

I don't understand. Bit-shift may take less CPU time but it's much more difficult conceptually. The actual operation being done is division by 2 and rounding down, bit-shift is the specific code used to do it.

As someone that knows a little bit about CPUs and digital logic, I can promise you that the right shift operation is not done by divide-and-round, it is done in dedicated hardware called a shifter that literally shifts bits. It might be harder for laymen to understand, but programmers (and CPUs) understand shift very literally.

Look, we're not going to get anywhere if you keep misinterpreting what I say. Of course how a CPU physically does a bit shift is completely different from how it does integer division. That's why I said it's faster. But the mathematical operation being performed is the same. Do you really find "block reward starts at 5 billion satoshis, and halves every 4 years" less intuitive than "block rewards starts at 5 billion satoshis, and is shifted by 1 bit to the right every 4 years"?

It seems to me we're speaking completely different languages - you as a programmer (I presume?) are passionate about implementation details (and you interpret everything I say as an implementation specification which must be rigorous), for me as a mathematician the concepts come first, the implementation can be worried about later - especially in those cases when it is clear that how we choose to implement it is not going to matter.

Quote from: kjj on May 08, 2012, 05:38:20 PM

I maintain that it is very important, and that it should be exact and simple, barring a very good reason to be otherwise.

As I said, I agree with this, but I don't see how what I'm talking about is any less simple or exact. The claim that bit-shift is somehow more exact than integer division is ludicrous.

Quote from: kjj on May 08, 2012, 05:38:20 PM

I think that this is the part that needs the most work. Miners will seek to maximize things based on whatever incentive scheme we come up with. We need to show that there is a problem (or at least a sub-optimal condition) and that this change fixes (or at least improves) it.

I agree with you that 600 seconds forever is very unlikely to be optimal. But is dynamic actually any better? If we make it dynamic, and set up a system that adjusts based on the desires of miners, and miners adjust things to their liking, is that evidence that the new value is better? Or is it just evidence that the miners are gaming the incentive? And how do we measure better-ness anyway?

The users, who are the second half of the equation, would need to have influence over the incentive structure of the miners. I still need to iron out a few things with this.