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Re: 0.30000000000000004

#81

Post by crazygringo »

snickerbockers wrote: post #48
Ididntdothis wrote: post #6

I still remember when I encountered this and nobody else in the office knew about it either. We speculated about broken CPUs and compilers until somebody found a newsgroup post that explained everything. Makes me wonder why we haven't switched to a better floating point model in the last decades. It will probably be slower but a lot of problems could be avoided.

There is no "better floating point model" because floating point will always be floating point. Fixed point always has been and always will be an option if you don't like the exponential notation.

> Fixed point always has been and always will be an option

Not really. It would be really cool if fixed point number storage were an option... but I'm not aware of any popular language that provides it as a built-in primitive along with int and float, just as easy to use and choose as floats themselves.

Yes probably every language has libraries somewhere that let you do it where you have to learn a lot of function call names.

But it would be pretty cool to have a language with it built-in, e.g. for base-10 seven digits followed by two decimals:

  fixed(7,2) i;
  i = 395.25;
  i += 0.01;
And obviously supporting any desired base between 2 and 16. Someone please let me know if there is such primitive-level support in any mainstream language!

Re: 0.30000000000000004

#82

Post by Dylan16807 »

hyperpape wrote: post #64
jonny_eh wrote: post #36

> It's actually pretty simple The explanation then goes on to be very complex. e.g. "it can only express fractions that use a prime factor of the base". Please don't say things like this when explaining things to people, it makes them feel stupid if it doesn't click with the first explanation. I suggest instead "It's actually rather interesting".

I rather like http://fabiensanglard.net/floating_point_visually_explained/

It's nice but it's extremely overkill for understanding this particular problem.

Re: 0.30000000000000004

#83

Post by monster_group »

_bxg1 wrote: post #79
_y5hn wrote: post #67

Earlier quoted context omitted.

It's actually in use in many places, for things like handling currency and money, and for when you get funny corner cases involving rounding such numbers and pooling the change. Whenever I see someone handling currency in floats, something inside me wither and die a small death.

I haven't worked in fintech but I've read that money is often represented (at least in storage) as plain integers, since for example US currency only ever goes to two decimal places. But I guess once you start operating on it you run into potential truncation unless you use rationals.

>>...since for example US currency only ever goes to two decimal places

That is not correct. Stock settlement transactions often list four decimal places.

Re: 0.30000000000000004

#84

Post by School-Cotton »

mcv wrote: post #20

The big issue here is what you're going to use your numbers for. If you're going to do a lot of fast floating point operations for something like graphics or neural networks, these errors are fine. Speed is more important than exact accuracy. If you're handling money, or numbers representing some other real, important concern where accuracy matters, most likely any number you intend to show to the user as a number, f…

Decimal numbers are not conceptually any more or less exact than binary numbers. For example, you can't represent 1/3 exactly in decimal, just like you can't represent 1/5 exactly in binary.

When handling money, we care about faithfully reproducing the human-centric quirks of decimal numbers, not "being more accurate". There's no reason in principle to regard a system that can't represent 1/3 as being fundamentally more accurate because it happens to be able to represent 1/5.

Re: 0.30000000000000004

#85

Post by 4ntonius8lock »

jonny_eh wrote: post #36

> It's actually pretty simple The explanation then goes on to be very complex. e.g. "it can only express fractions that use a prime factor of the base". Please don't say things like this when explaining things to people, it makes them feel stupid if it doesn't click with the first explanation. I suggest instead "It's actually rather interesting".

For including words in a sale pitch, I'd agree.

But this isn't a sales pitch. Some people are just bad at things. The explanation on that page require grade school levels of math. I think math that's taught in grade school can be objectively called simple. Some people suck at math. That's ok.

I'm very geeky. I get geeky things. Many times geeky things can be very simple to me.

I went to a dance lesson. I'm terribly uncoordinated physically. They taught me a very 'simple' dance step. The class got it right away. The more physically able got it in 3 minutes. It took me a long time to get, having to repeat the beginner class many times.

Instead of being self absorbed and expect the rest of the world to anticipate every one of my possible ego-dystonic sensibilities, I simply accepted I'm not good at that. It makes it easier for me and for the rest of the world.

The reality is, just like the explanation and the dance step, they are simple because they are relatively simple for the field.

I think such over-sensitivity is based on a combination of expecting never to encounter ego-dystonic events/words, which is unrealistic and removes many/most growth opportunities in life, and the idea that things we don't know can be simple (basically, reality is complicated). I think we've gotten so used to catering to the lowest common denominator, we've forgotten that it's ok for people to feel stupid/ugly/silly/embarrassed/etc. Those bad feelings are normal, feeling them is ok, and they should help guide us in life, not be something to run from or get upset if someone didn't anticipate your ego-dystonic reaction to objectively correct usage of words.

Re: 0.30000000000000004

#87

Post by bwilliams18 »

_bxg1 wrote: post #79
_y5hn wrote: post #67

Earlier quoted context omitted.

It's actually in use in many places, for things like handling currency and money, and for when you get funny corner cases involving rounding such numbers and pooling the change. Whenever I see someone handling currency in floats, something inside me wither and die a small death.

I haven't worked in fintech but I've read that money is often represented (at least in storage) as plain integers, since for example US currency only ever goes to two decimal places. But I guess once you start operating on it you run into potential truncation unless you use rationals.

US currency can go to more than two decimal places...

http://blogs.reuters.com/ben-walsh/2013/11/18/do-stocks-real...

I guess it's time for someone to write an "Assumptions Programmers make about money" post.

Re: 0.30000000000000004

#88

Post by saagarjha »

virtualparrot wrote: post #76
pmarreck wrote: post #63

IEEE floating-point is disgusting. The non-determinism and illusion of accuracy is just wrong. I use integer or fixed-point decimal if at all possible. If the algorithm needs floats, I convert it to work with integer or fixed-point decimal instead. (Or if possible, I see the decimal point as a "rendering concern" and just do the math in integers and leave the view to put the decimal by whatever my selected precision…

I agree with this view, there's nothing more disgusting than non-determinism. The way computers rely on assumptions for the accuracy of a floating number is one that's contrary to the principles of logical thinking.

> The way computers rely on assumptions

The way people rely on assumptions.

Re: 0.30000000000000004

#89

Post by School-Cotton »

saagarjha wrote: post #77
threatofrain wrote: post #62

Use Int types for programming logic.

Except when, you know, you can’t.

Curious, when can't you?

My mental model of floating-point types is that they are useful for scientific/numeric computations where values are sampled from a probability distribution and there is inherently noise, and not really useful for discrete/exact logic.

Re: 0.30000000000000004

#90

Post by hutzlibu »

gowld wrote: post #39

This is a great shibboleth for identifying mature programmers who understand the complexity of computers, vs arrogant people who wonder aloud how systems developers and language designers could get such a "simple" thing wrong.

" vs arrogant people who wonder aloud how systems developers and language designers could get such a "simple" thing wrong."

I never heard anyone complain that it would be simple to fix. But complaining? Yes - and rightfully so. Not every webprogrammer need to know the hw details and don't want to, so it is understandable that this causes irritation.

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