Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

tigerbeetle.com

Post reply on HN
Print view View original

191–200 of 372 posts

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

#191

Post by Jabrov »

tech_ken wrote: post #172

>Surprisingly, we also don’t use negative numbers (you may have encountered software ledgers that store only a single positive/negative balance). Instead, we keep two separate strictly positive integer amounts: one for debits and another for credits. It's funny I've always thought of two-column bookkeeping as a kludge that was invented because the author was unaware of negative numbers. But here there's actually a ju…

How are they superior though? What do they gain by doing this (other than added complexity)?

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

#192

Post by lxgr »

helpfulmountain wrote: post #189
vidarh wrote: post #184

Earlier quoted context omitted.

A shocking number of people (edit: who implement billing related software) are unaware of how many decimal points of accuracy their local tax code requires to calculate vat or sales tax correctly. And those things are often specified in terms of arithmetic correctness. I had our CFO stand behind me while I talked him through every step of our VAT calculations once, because he was legally responsible if I made us roun…

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

If there's an applicable law or regulation that says "you must do x", and you do y (and that yields different results), you'll get into trouble, even if your way yields "better" or "more accurate" results.

This is not to say that using floats and rounding correctly necessarily does yield different results, by the way (although most likely it will) – but if they do differ, you're going to have a bad time using floats.

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

#193

Post by cmovq »

helpfulmountain wrote: post #189
vidarh wrote: post #184

Earlier quoted context omitted.

A shocking number of people (edit: who implement billing related software) are unaware of how many decimal points of accuracy their local tax code requires to calculate vat or sales tax correctly. And those things are often specified in terms of arithmetic correctness. I had our CFO stand behind me while I talked him through every step of our VAT calculations once, because he was legally responsible if I made us roun…

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

https://0.30000000000000004.com/

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

#194

Post by robertlagrant »

vidarh wrote: post #184
lxgr wrote: post #145

Earlier quoted context omitted.

The article is about data types for storage, not for intermediary values used as part of calculations, though. Are you proposing that everybody is storing monetary values "wrong", too? And as a meta-point: > I have been fighting over this with countless people, teams and companies. [...] I have never in my life joined a software project for any organisation that was able to do basic arithmetic on money correctly [...…

A shocking number of people (edit: who implement billing related software) are unaware of how many decimal points of accuracy their local tax code requires to calculate vat or sales tax correctly. And those things are often specified in terms of arithmetic correctness. I had our CFO stand behind me while I talked him through every step of our VAT calculations once, because he was legally responsible if I made us roun…

> A shocking number of people are unaware of how many decimal points of accuracy their local tax code requires to calculate vat or sales tax correctly.

I would imagine almost no-one knows this (-: What's a shocking number?

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

#195

Post by wrs »

helpfulmountain wrote: post #189
vidarh wrote: post #184

Earlier quoted context omitted.

A shocking number of people (edit: who implement billing related software) are unaware of how many decimal points of accuracy their local tax code requires to calculate vat or sales tax correctly. And those things are often specified in terms of arithmetic correctness. I had our CFO stand behind me while I talked him through every step of our VAT calculations once, because he was legally responsible if I made us roun…

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

Laws are typically written by humans, and we use base 10, not base 2. We think $0.03 is an exact number, but floats can’t represent 0.03 exactly.

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

#196

Post by j16sdiz »

vidarh wrote: post #184
lxgr wrote: post #145

Earlier quoted context omitted.

The article is about data types for storage, not for intermediary values used as part of calculations, though. Are you proposing that everybody is storing monetary values "wrong", too? And as a meta-point: > I have been fighting over this with countless people, teams and companies. [...] I have never in my life joined a software project for any organisation that was able to do basic arithmetic on money correctly [...…

A shocking number of people (edit: who implement billing related software) are unaware of how many decimal points of accuracy their local tax code requires to calculate vat or sales tax correctly. And those things are often specified in terms of arithmetic correctness. I had our CFO stand behind me while I talked him through every step of our VAT calculations once, because he was legally responsible if I made us roun…

in my experience, these are often written off as error.

if the error is less than their hourly salary rate, it don't even worth mentioning.

if it worth a day or two of salary, its nice to fix but never a priority

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

#197

Post by GeneralMayhem »

helpfulmountain wrote: post #189
vidarh wrote: post #184

Earlier quoted context omitted.

A shocking number of people (edit: who implement billing related software) are unaware of how many decimal points of accuracy their local tax code requires to calculate vat or sales tax correctly. And those things are often specified in terms of arithmetic correctness. I had our CFO stand behind me while I talked him through every step of our VAT calculations once, because he was legally responsible if I made us roun…

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

Floats lose precision unexpectedly with certain fractions that are perfectly representable in decimal, and also with certain integers once you get high enough.

The standard in ad-tech (not sure about banking) is to use int64s representing either microdollars or microcents, so a max capacity of 9.3*10^13 or 10^11 dollars

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

#198

Post by macksd »

helpfulmountain wrote: post #189
vidarh wrote: post #184

Earlier quoted context omitted.

A shocking number of people (edit: who implement billing related software) are unaware of how many decimal points of accuracy their local tax code requires to calculate vat or sales tax correctly. And those things are often specified in terms of arithmetic correctness. I had our CFO stand behind me while I talked him through every step of our VAT calculations once, because he was legally responsible if I made us roun…

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 have a "decimal" type intended for currency, etc. and then they won't make all the same mistakes, but as the OP said you still need to control rounding rules and make sure they match the law.

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

#199

Post by Izkata »

ben_w wrote: post #90
jon-wood wrote: post #66

Earlier quoted context omitted.

That “just” is doing some very heavy lifting. That could potentially involve having to update almost every financial system worldwide given the US dollar’s position as a global reserve currency.

If inflation averages 5% per year, a factor of 10^17 (what are the biggest USD notes actually in use?) is just over 800 years away, which is far enough that we might legitimately not have a moon any more let alone dollars. If hyperinflation brings that date closer, the dollar will probably also stop being a global reserve. Or possibly: will be caused by it ceasing to be a global reserve.

The federal reserve aims for 2% a year, their adjustments just haven't been working.

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

#200

Post by undersuit »

jkestner wrote: post #133
lnxg33k1 wrote: post #71

We could also tax everything above 32 bits, good for people, good for machine

Imagine if the most money you could have is $43 million (rounding!), and it rolled over to 0 if you exceeded that. You'd be paying accountants to keep you as close to the limit as you dare, instead of just cheating on taxes. But not paying them too much, as you're only a multimillionaire.

I guess at some point you just hire accountants to throw mini basketballs at mini hoops. Most efficient way to keep you below $43 million.
Post reply on HN