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64-bit bank balances ‘ought to be enough for anybody’?

tigerbeetle.com

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Re: 64-bit bank balances ‘ought to be enough for anybody’?

#281

Post by hot_gril »

JeremyNT wrote: post #276
hot_gril wrote: post #274

> For the same reason, digital currencies are another use case for 128-bit balances, where again, the smallest quantity of money can be represented on the order of micro-cents (10-6)… or even smaller. To give a concrete example, Ethereum has a lot of precision (1 ether = 10^18 wei), and there are like 120M ether, so that's more than 64 bits just to represent the supply. Idk though, is this a real concern with traditi…

> Idk though, is this a real concern with traditional finance? Zimbabwe had their huge bills, but I assume the small ones were unused. Just like you round US cents, you could probably round their currency at some cutoff. If you were processing Ether outside the blockchain, you'd probably round somewhere too. Yeah... I started reading this article and was waiting for the crypto angle, because in normal finance I don't…

Even in cryptocurrency, I feel like the level of precision is mainly aspirational + cuz they can. Who cares about 1 wei in the context of a transaction that costs around 100 trillion wei on its own? The smallest unit of ether I've ever seen in any kind of UI is 1 gwei (1 billion wei).

Re: 64-bit bank balances ‘ought to be enough for anybody’?

#282

Post by Dylan16807 »

macksd wrote: post #198
helpfulmountain wrote: post #189

Earlier quoted context omitted.

Why would it be wrong to use floats? That would have been my default assumption

When you're doing floating point arithmetic on a computer, it will approximate and round certain values in ways that don't match the way humans do it when they're, e.g. doing accounting. So you need to run a massive physics simulation really fast? Yes, floats are great. You need to calculate taxes on a massive corporation's fiscal year? Bad idea. Some libraries advertise "arbitrary precision", many computer systems h…

> You need to calculate taxes on a massive corporation's fiscal year? Bad idea.

That depends on whether the hundred-billion-dollar corporation cares about being off by a dollar.

And by "off" I mean "different from how humans round", not necessarily further away from an infinite-precision calculation. In fact at "massive corporation" level I would guess that binary floating point is more accurate than a typical fractional penny system.

Re: 64-bit bank balances ‘ought to be enough for anybody’?

#283

Post by Dylan16807 »

ilyt wrote: post #207
helpfulmountain wrote: post #189

Earlier quoted context omitted.

Why would it be wrong to use floats? That would have been my default assumption

> 0.3-0.2-0.1 -2.7755575615628914e-17 And now you overdrafted

Decimal systems have to round too, so that's a pretty weak dismissal.

Re: 64-bit bank balances ‘ought to be enough for anybody’?

#284

Post by ben_w »

feoren wrote: post #270
ben_w wrote: post #261

Earlier quoted context omitted.

https://en.wikipedia.org/wiki/Self-replicating_spacecraft Even the unit of replication is a factory under human control with no novel AI, and which can only replicate with significant human oversight of already existing mining, processing, and manufacturing equipment, it doesn't take insane reproduction rates to disassemble the moon in 800 years.

That's like saying "5 years away is far enough that Mount Rushmore might be gone by then!" because we could nuke it if we wanted to. Why would we do that!? We like the moon being there! Do these examples really help illustrate how far away 800 years, or 5 years, are?

Lots of people want to build megastructures, and the moon is convenient material; I suspect that when the capabilities make it seem like a serious possibility, people will discover the problems and then do it anyway just like with almost all the other environmental issues to date that compete against economic interests.

However, the main point of the example is "800 years is too far ahead to plan for how much the US dollar might inflate" by way of demonstrating how extreme things can change. As far as I know, no fiat currency has existed that long, and only three country-like entities[0].

Mount Rushmore isn't likely to be targeted by nukes, but I strongly suspect that it is defended against vandals (politically motivated or otherwise) with dynamite (or similar categories of explosives) — that said, if you've always wanted to go and have not yet done so, you should, as I could've said much the same thing about the World Trade Centre 22 years and a fortnight ago.

(I wonder if a single unfriendly nuke on US soil would cause an economic shock? Normally the assumption would be what else might come with it).

[0] https://www.brainscape.com/academy/longest-lasting-empires-w...

Re: 64-bit bank balances ‘ought to be enough for anybody’?

#285

Post by returningfory2 »

walnutclosefarm wrote: post #258

I'd like a report back from TigerBeetle on how many applications they actually support where the high order 64 bits are nonzero. I would note that the entire US GDP is less than 10^15 cents, and that 2^64 accommodates just shy of 10^19 in signed integers. So, even if your database had a justification for thousands of a cent transactions (not intermediate results, but recordable transactions), you'd still need to have…

There's one small part of the article that IMO is sort of key to understanding the why:

> [for every account] we keep two separate strictly positive integer amounts: one for debits and another for credits

It is not sufficient that their integer type is able to handle individual transactions. Their integer type must be able to handle the sum of the absolute value of all transactions that have occurred on an account. And I think it's easy to come up with realistic situations where you hit that.

So say you take the NYSE, which trades about ~$18 billion per day [0]. This is ~$1.8 trillion cents, or about 2^51 microcents. After 2^12 business days (~=16 years) you'll already be hitting the limit. (This is just a toy example ofc.)

[0] https://www.nyse.com/trading-data#:~:text=The%20New%20York%2....

Re: 64-bit bank balances ‘ought to be enough for anybody’?

#286

Post by jorangreef »

JeremyNT wrote: post #276
hot_gril wrote: post #274

> For the same reason, digital currencies are another use case for 128-bit balances, where again, the smallest quantity of money can be represented on the order of micro-cents (10-6)… or even smaller. To give a concrete example, Ethereum has a lot of precision (1 ether = 10^18 wei), and there are like 120M ether, so that's more than 64 bits just to represent the supply. Idk though, is this a real concern with traditi…

> Idk though, is this a real concern with traditional finance? Zimbabwe had their huge bills, but I assume the small ones were unused. Just like you round US cents, you could probably round their currency at some cutoff. If you were processing Ether outside the blockchain, you'd probably round somewhere too. Yeah... I started reading this article and was waiting for the crypto angle, because in normal finance I don't…

Yes, we actually held out on the digital currency angle.

What tipped the scales, was realizing that this applied also in normal finance, especially exchanges (not crypto) that operate with high precision: https://news.ycombinator.com/item?id=37573939

Re: 64-bit bank balances ‘ought to be enough for anybody’?

#287

Post by hot_gril »

jorangreef wrote: post #280
walnutclosefarm wrote: post #258

I'd like a report back from TigerBeetle on how many applications they actually support where the high order 64 bits are nonzero. I would note that the entire US GDP is less than 10^15 cents, and that 2^64 accommodates just shy of 10^19 in signed integers. So, even if your database had a justification for thousands of a cent transactions (not intermediate results, but recordable transactions), you'd still need to have…

To be fair, I used to think like this too, but chatting with multiple large exchanges/brokerages made us realize this was a thing. > less than 10^15 cents There are systems that don't work in terms of cents (cf. the examples of issues in many of the comments here), or even in thousandths of a cent, but with significantly more precision. Literally, in other words: Where you run into problems then, with 10 ^ n integer…

Why do exchanges use such high precision for fractions?

Re: 64-bit bank balances ‘ought to be enough for anybody’?

#289

Post by cperciva »

masklinn wrote: post #225
amalcon wrote: post #170

Earlier quoted context omitted.

Integer cents is fantastic for POS software and similar things that deal with at most a few thousand dollars at a time. The place where it starts to fail is when the absolute numbers get really large, not really small. Think "United States Federal Reserve" or "UBS". Then remember that some of these institutions need to deal with accounts denominated in Zimbabwean dollars.

Really small can be an issue when it gets really small e.g. tarsnap’s accounting is pretty infamously done in attodollars (1e-12). U64 only has room for 19 decimal digits so you’re limited to 7 figures up.

Tarsnap's pricing is in picodollars (1e-12) but the accounting is attodollars (1e-18). Tarsnap uses 128-bit balances -- 64 bits of attodollars and 64 bits of whole dollars.

If I ever have someone paying me more than 2^64 dollars, I'll rewrite Tarsnap's accounting system.

Re: 64-bit bank balances ‘ought to be enough for anybody’?

#290

Post by jorangreef »

hot_gril wrote: post #287
jorangreef wrote: post #280

Earlier quoted context omitted.

To be fair, I used to think like this too, but chatting with multiple large exchanges/brokerages made us realize this was a thing. > less than 10^15 cents There are systems that don't work in terms of cents (cf. the examples of issues in many of the comments here), or even in thousandths of a cent, but with significantly more precision. Literally, in other words: Where you run into problems then, with 10 ^ n integer…

Why do exchanges use such high precision for fractions?

To represent prices that are traded fractionally.
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