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

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

#301

Post by ignite »

forinti wrote: post #43
onetimeuse92304 wrote: post #24

Specialising in financial software, over the past 2 decades I have been fighting over this with countless people, teams and companies. For accounting you should only ever use arbitrary precision math library with ability to specify rounding rules. If your programming environment/language does not have one, it is unsuitable to be used for accounting, billing, invoicing, payments, etc. Having the underlying library is,…

I have a personal anecdote on this subject. A long time ago I worked at a bank and I had to calculate a large number of accounts regarding agricultural loans. These were state sponsored loans. When I finished my task (this was a Java job), I found that sometimes the results were off by $0.01. So I asked my boss how I should do the rounding, to which he replied that an error of up to $1 was acceptable. If I recall cor…

People care less about the dollar value than about reconciling. If there is some external system they should match, they really want it to match exactly.

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

#302

Post by hot_gril »

jorangreef wrote: post #297
hot_gril wrote: post #292

Earlier quoted context omitted.

But nothing can do that exactly, for example 1/3 has an infinitely long decimal or binary representation. So why round to 10^-10 as opposed to something like 10^-3?

For sure. We didn't pick 10^10 scaling. It's just what some massive brokerages/exchanges actually use. The fact that these were not necessarily crypto made us take note. At the same time, you can understand that 10^10 scaling is at least significantly more precise. And I can imagine these things are viral too, who you trade with, also determines your minimum resolution. You can always downsample in presentation, but…

Yeah, was just curious if the brokerages explained their reasoning in detail. Even if it's just viral, someone big had to have a reason to start the trend.

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

#303

Post by ta1243 »

vidarh wrote: post #212
itsoktocry wrote: post #205

Earlier quoted context omitted.

> 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. What is your jurisdiction? In Canada, I can't for the life of me imagine the CRA would remotely care about decimal-point accuracy. In fact, most of their online forms explicitly remove the decimals.

UK. The rules may have changed now, it's a long time since I implemented the rounding rules here, but the last time I did it required 5 decimals accuracy. The rules also used to specify how you needed to account for line items vs. sub-totals in your invoices to ensure you didn't find any "workarounds" to shave off some pennies of tax (In fact, the last time was while the tax authority was still called the Inland Reve…

> For aggregate totals of your VAT liability across your total set of invoices, you'd be fine with rounding up to the nearest pound, to the Inland Revenue's benefit

On personal tax forms you have to round in the taxpayer favour. If your income is 12345.67 you round it to 12345. If your expense (say giftaid) is 12345.67 you round it to 12346.

Surprised it's the other way with VAT, but then I do very little with tax other than click a few buttons and confirm "yes, you have to tax me as I have children".

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

#304

Post by dvlsg »

weinzierl wrote: post #230

I once argued for using BigDecimal instead of Doubles in an invoicing software but had a hard time to come up with a practically relevant example. Is there an example where it makes a noticeable difference (at least one cent in the final result) that does not involve unrealistic amounts or numbers of items? I'm not arguing for Doubles, just collecting arguments to convince.

Technically you can have noticeable differences before you even make it to 1 cent. For example, if you're trying to determine if a result of a calculation is negative, 0, or positive for whatever reason. With floats/doubles, you would probably need to consider "0" to actually be "a number sufficiently close to 0, if not 0 exactly" and then remember to handle that everywhere.

It can also be noticeable if you're just trying to calculate something like "is the invoice paid off". Maybe your view layer is showing $0.00 balance to the end user, but the backend hasn't correctly rounded off those extra bits from a floating point calculation, so your backend logic is now saying the invoice is not actually fully paid off, even if the end user has no idea what they could possibly still owe.

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

#305

Post by ta1243 »

leosarev wrote: post #271
vidarh wrote: post #256

Earlier quoted context omitted.

If you report 1,000,000 and certify that it's the right number, and the government audits you and find you should have paid 1,010,000, then depending on jurisdiction you might be entirely ok, or you might find you're not going to be paying just the difference, and interest, but also a fine, and bearing the cost of additional audits going forward, and that your finance director will not appreciate having to address qu…

It's strange. In Russia, small error in VAT will get you a letter from tax service "pay us a small error voluntarily, or we will schedule an inspection". Letter will be automatically generated by ASK-NDS system (translated as Auto Check Vat).

How do they know there's an error?

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

#306

Post by [deleted] »

kemotep wrote: post #244
kybernetikos wrote: post #63

Earlier quoted context omitted.

I believe that economists generally think that a small amount of inflation is good for the economy, and that deflation is bad (because it leads to reductions in spending and investment, potentially causing a vicious circle). It's also relatively easy to counteract - just print more. In order for hyperdeflation to occur you'd need a currency where the issuing body didn't believe deflation was bad, or didn't care.

Bitcoin has a hyper deflationary monetary policy hard coded in.

[deleted]

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

#307

Post by [deleted] »

ignite wrote: post #299
HWR_14 wrote: post #273

Earlier quoted context omitted.

The current US national debt represented in integer cents requires 52 bits. It can trivially increase 4,000x before we need to worry about 64-bit balances.

Peak inflation in Argentina was 20262.80%. So, not as much margin as one might think.

[deleted]

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

#308

Post by elcritch »

Merad wrote: post #248
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…

A shocking number of people who work with software that handles money are just winging it. I worked on a project once that handled payment processing functionality for other products at the company (it was a B2B SaaS where clients could take payments through our software). We also handled payments related billing, since the clients would owe fees to us and to our payments gateway for their transactions. The payments…

Carrying the remainder microcents as a bill seems overkill and not necessarily correct. Accounting regulations and accepted practices have well established rules on rounding, like bankers rounding (1).

You could probably treat the extra microcents as being on the next pay period. Though that's annoying as if I close an account I'd expect it to be paid in full, not a few microcents remaining.

1: https://stackoverflow.com/questions/45223778/is-bankers-roun...

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

#309

Post by Dylan16807 »

Merad wrote: post #298
Dylan16807 wrote: post #279

Earlier quoted context omitted.

Why was it listed separately at all? If the month's charges were 406.783228 and I get a bill for 406.79 then that seems perfectly good. If I get a bill that says 406.78, plus a separate 0.01, that's weird.

> Why was it listed separately at all? Because the bill included a detailed breakdown of all the fees by type and transaction. Typically our clients were charged a fixed monthly fee, a fixed authorization fee charged every time a payment was attempted (even if it was declined), and a fee applied to successful payments that was a percentage of the payment amount. There were other fees for things like processing charge…

I wasn't talking about rounding up. I meant exactly the same thing you're saying about month 4.

> Because the bill included a detailed breakdown of all the fees by type and transaction.

Was it all rounded [down] to the nearest penny?

That type of bill can already fail to add up to the total very easily, like x.xx4 + x.xx4 + x.xx4. So I'm still not sure why there was a need to have a line item to explain this single penny.

Was there only a single charge on each bill that used fractional pennies? So that this was the only time that things wouldn't add up perfectly?

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

#310

Post by Dylan16807 »

hiatus wrote: post #293
Dylan16807 wrote: post #282

Earlier quoted context omitted.

> 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 fracti…

> That depends on whether the hundred-billion-dollar corporation cares about being off by a dollar. How many hundred billion dollar corporations are private? Public companies would care a great deal about accounting accuracy.

Is it worse for a hundred billion corp to be off by a dollar than for a hundred million corp to be off by a third of a penny?
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