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How does your programming language handle “minus zero” (-0.0)?

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Re: How does your programming language handle “minus zero” (-0.0)?

#81

Post by steerablesafe »

Spivak wrote: post #55
steerablesafe wrote: post #43

Earlier quoted context omitted.

I'm well aware of nonstandard analysis, but ∞ is still not a number there, even though there are infinitely many infinitely large elements .

The extended complex plane is a space where inf is actually number and where division by zero is allowed. Same with the extended real line. Infinity is as much a number as it is useful to define it as such.

Ah right, I forget that extending with a single infinity element is useful with complex numbers and with geometry. It's still not very common with the reals alone as +∞ and -∞ are reasonable to want as separate elements there, but it doesn't play nicely with 1/0 that way.

Re: How does your programming language handle “minus zero” (-0.0)?

#82

Post by bluecalm »

Const-me wrote: post #59
patrec wrote: post #30

Earlier quoted context omitted.

When does this need arise? Well, otherwise inverting a value can change it's sign and in particular inverting -∞ twice will give you +∞, and being off by "2∞" is a pretty large error for a lot of computations ;) You can end up with zeros and infinities pretty easily because you overflow or underflow the range of floating point precision, and generally you want something sensible to happen in typical cases, even if so…

> If anyone knows why this design was not chosen and what fundamental downsides it has, I'd love to hear it. No fundamental ones, but a few practical. 32-bit numbers have 2^32 unique values, the number is even. Your approach makes the range asymmetrical like it happens with integers. The range for 8-bit signed integers is [ -128 .. +127 ]. On ARM NEON there’re two versions of integer negate and absolute instructions,…

I wonder if it would be useful to have a signed integer that has symmetric range and the one that is left is used as NaN. Overflows would set it to NaN for example. Then again, once that's on the table it's very tempting to steal two more values for +/- inf. I think it's very useful to have full range unsigned ints but signed ones could have range reduced to make them less error prone.

Re: How does your programming language handle “minus zero” (-0.0)?

#83

Post by linkdd »

quelsolaar wrote: post #78
linkdd wrote: post #70

Earlier quoted context omitted.

I never said it was easier and I never said ALL game engines. And computing integers IS faster than computing floats, at least on a CPU.

>And computing integers IS faster than computing floats, at least on a CPU. In the abstract yes. In reality not so much. A lot of what floats are used for in games is vector math (you are often in a 2D/3D world), and vector math in fixed point requires a lot more work in integer math since you constantly need to shift down things in order to avoid overflow. Overflow bugs are a constant problem when doing dot products…

I never use the square root in games, I always compare squared distances (since the properties are the same).

If you try to do with Fixed Point Arithmetic what was intended to be done with Floating Point, you're the problem.

A 32 bits integer can hold values up to 4 billions, if I have that kind of value in a simple game, then yes i will switch to Floating Point Arithmetic, but when does that use case happen if you're not writing a physic simulation game ?

Re: How does your programming language handle “minus zero” (-0.0)?

#84

Post by pfraze »

quelsolaar wrote: post #65
TorKlingberg wrote: post #60

I feel like floating point is a completely separate branch of programming that a lot of coders never use. When they do it's often a mistake, like for currency. Yet floating point is very useful for scientific calculations and simulations, which is what computers were all about for the first couple of decades. I have a suspicion that on a fundamental level, floating point isn't actually good for games or machine learn…

As someone who has started out making games on Playstation 1 that didn't have floating point hardware, I can with authority say that developing games with only integers suck. Floating point number are far easier and robust to use.

Only integers? Wow. Were int pairs used to represent numbers with decimals or what?

Re: How does your programming language handle “minus zero” (-0.0)?

#85

Post by oivey »

TorKlingberg wrote: post #60

I feel like floating point is a completely separate branch of programming that a lot of coders never use. When they do it's often a mistake, like for currency. Yet floating point is very useful for scientific calculations and simulations, which is what computers were all about for the first couple of decades. I have a suspicion that on a fundamental level, floating point isn't actually good for games or machine learn…

Lots of the math in games and ML assumes you’re operating in the reals. For example, the optimization in neural networks. Integers and fixed point won’t work.

Re: How does your programming language handle “minus zero” (-0.0)?

#86

Post by JoeAltmaier »

Signed infinity is nowhere near the 'expected result'. Zero has no sign. NAN would be a better result off the top of my head.

But I see from the standard that dividing by zero returns infinity with the xor of the dividend and divisor. This also makes no sense - since zero has no sign, its not possible to tell what kind of infinity would result. It's strange that the standard permits both the infinity result from dividing by zero, and simultaneously supports signed zero.

Re: How does your programming language handle “minus zero” (-0.0)?

#88

Post by timerol »

pfraze wrote: post #84
quelsolaar wrote: post #65

Earlier quoted context omitted.

As someone who has started out making games on Playstation 1 that didn't have floating point hardware, I can with authority say that developing games with only integers suck. Floating point number are far easier and robust to use.

Only integers? Wow. Were int pairs used to represent numbers with decimals or what?

To use only integers, you generally try to express all numbers in units of the smallest quantity. So any money is in integer cents, any distance is in integer (spatial resolution size). It gets annoying with derived units: Time can be stored in integer frames, but then you'll need a rational type of some kind to properly handle velocity. Or you just round to the nearest (spatial resolution) per frame and hope the errors don't look too weird on the other side.

Re: How does your programming language handle “minus zero” (-0.0)?

#89

Post by bwestergard »

oivey wrote: post #85
TorKlingberg wrote: post #60

I feel like floating point is a completely separate branch of programming that a lot of coders never use. When they do it's often a mistake, like for currency. Yet floating point is very useful for scientific calculations and simulations, which is what computers were all about for the first couple of decades. I have a suspicion that on a fundamental level, floating point isn't actually good for games or machine learn…

Lots of the math in games and ML assumes you’re operating in the reals. For example, the optimization in neural networks. Integers and fixed point won’t work.

Floats have a totally different algebra than the reals, though.
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