Here's a few of the basic types: if (x == 0.5) All of the integers from 0 to 2^24 (about 16 million) are representable in a float, and many more are representable in a double, and most of them don’t end in 5. Post was not sent - check your email addresses! Switch to Manual. If you are dealing with large arrays of them then the memory savings (and reduced cache misses) can be critical. It depends on how you compiled your Pike compiler and if you didn’t add some specific flags, then it depends on architecture. Double: The double accommodates 15 to 16 digits, compared with float's seven. public static int RoundToInt (float f); Description. Float vs. Here is a typical example of the code that triggers this: float x = 1.1;if (x != 1.1) printf(“OMG! Cancel. Float uses 1 bit for sign, 8 bits for exponent and 23 bits for mantissa but double uses 1 bit for sign, 11 bits for exponent and 52 bits for the … Float - 32 bit (7 digits) In one of the examples, why do you use float(1.1) and (double)1.1, and thus not double(1.1)? Change ), You are commenting using your Google account. Of course, most of this trouble disappears if you use a high level language. More generally, I’d allow parameters to functions to indicate whether they should allow or disallow explicit casts, since there are situations where double-to-float should be accepted silently (e.g. Anyone know? Alternatively, I can work this using the design of the game rather than physics. C# supports the following predefined floating-point types:In the preceding table, each C# type keyword from the leftmost column is an alias for the corresponding .NET type. To convert the fractional part of a number to a particular base you just repeatedly multiply the number by the base. ), Pingback: How to: 0.1 float is greater than 0.1 double. But if you stick to the basic five operations (plus, minus, divide, multiply, square root) and you haven’t recompiled your code then you should absolutely expect the same results. FYI: In Pike float doesn’t default to double. New comments cannot be posted and votes cannot be cast. Forecast for randomascii: programming, tech topics, with a chance of unicycling. Don’t expect the result of double-precision calculations to equal the result of float-precision calculations, even when the only ‘calculation’ is converting from decimal to binary floating point. Precision is the main difference where float is a single precision (32 bit) floating point data type, double is a double precision (64 bit) floating point data type and decimal is a 128-bit floating point data type. Press question mark to learn the rest of the keyboard shortcuts. But first let’s practice base conversion. I can probably tackle this next week if you need me to. The problem isn’t the comparison, the problem is that people think 1.1 is a float constant. The double is 8 bytes long. If floating-point math is incapable of getting correct results when there are no calculations (except for a conversion) involved then it is completely broken. Basically you need to use 2 coordinate systems and move all the object in your current cluster (first coordinate Double) to 0,0,0 in unity and use your coordinates relative to the cluster center(2nd coordinate Float) as the actual transform coordinates. That expectation is incorrect – it is impossible to perfectly represent 1.1 in a binary float. In fact, if you take a randomly selected double then the odds of it being perfectly representable in a float are about one part in 4 billion. ANYWAY, the project I'm currently working on involves making a realistic model of the solar system - including realistic orbital dynamics (although, 2-body, not N-body, of course). Press J to jump to the feed. This is a very clear and straight explanation of how floats and doubles behave, and the extra about base conversion was very helpful to remember how it worked! Int - represent whole integer numbers. In some cases, comparing floating-point numbers for exact equality is actually correct. An awesome reminder of how to do base conversion and why we had to learn it in the first place! But all the prebuilt Pikes I’ve used have had a 64-bit ‘float’ type. Make your own math library with arbitrary precision, unless you're going to run thousands of small asteroids and stuff, and mostly focus on planets/moons, just make some 256bit fixed point number system by hand, something like Q128.128 should give you more precision than you need (i think). inputs to serialization or comparison functions). But flexibility comes at the cost of a LOT of work: with surface shaders, Unity takes care of all (almost) the PBR lighting and shadowing so you just have to worry about the shader itself. (See also PEP 393 strings. A programmer might write “float1 == double1” when genuinely intending “(double)float1 == double1”, which is how compilers would interpret it. The Singledata type stores single-precision floating-point values in a 32-bit binary format, as shown in the following table: Just as decimal fractions are unable to precisely represent some fractional values (such as 1/3 or Math.PI), binary fractions are unable to represent some fractional values. Most FPUs have a (per-thread) setting to control the rounding mode, and x87 FPUs have a setting to control register precision. exp, sin, etc.). The data is stored in memory. As a result Havok doesn’t need to use double-precision math (physics calculations are faster in single-precision mode). Not a great choice for numerical analysis. else Floats suck!” is that the code above is flawed in some way. Circular orbits were my first step (in learning C# and the unity environment) - now I'm wanting to expand it - and my design really requires me to be able to "swing" around planets :). As a case in point, all of Relic’s games have used floating-point extensively in gameplay code, but are still completely deterministic across CPUs from the Pentium II through the i7 — we know this because you can play networked games and replays on different generations of machine without desyncing. I'm certain I'm not the first person to have this problem, and I'm wondering if there is some setting in Unity that will cause the physics engine to use doubles or longs instead of floats. No more fiddling with float vs double. A good language should squawk in cases where there is genuine ambiguity about what a programmer most likely meant. Cancel. I do not believe that Unity has a public build that uses doubles by default. Tweak settings to your heart’s content In order to store them into float variable, you need to cast them explicitly or suffix with ‘f’ or ‘F’. The slight breaking of the pattern at the end of both numbers is because the conversion is done with round-to-nearest rather than truncation, in order to minimize the error in the approximation, and in both cases it is rounded up. Clustering is totally transparent to users, it runs in the background and you won’t see it. There was no reason. So the guarantee is really that the same machine code will produce the same results, as long as you don’t do something wacky. It’s also plausible that a programmer might accidentally write that when what was intended was “float1 == (float)double1”. An arbitrary precision float type is a great thing to have, but used carelessly it just gives you the same issues only with smaller epsilons. Unity is the ultimate game development platform. Two reasonable ways to fix the initial code would be: float x = 1.1f; // Float constantif (x != 1.1f) // Float constant printf(“OMG! Making a countdown timer in Unity involves storing a float time value and subtracting the duration of the last frame (the delta time) ... made up of two double-digit numbers that are separated by a colon (00:00). On today’s hardware, I’m not sure there’s even any benefit left at all – in the same way that there’s no real benefit to working with 16-bit integers rather than 32-bit, because moving them around in memory usually involves just as much work. And no angels harmed. The limitation for the X, Y and Z Position Transform is 7 significant digits, with a decimal place anywhere within those 7 digits; in effect you could place an object at 12345.67 or 12.34567, for just two examples. I could feasibly do what I'm trying to accomplish in two ways: The first would be to go ahead and split the space up into clusters, maintaining the vector and distance towards the sun for each object (I'm operating in 2D, not worrying about 3D yet, which makes coding "real" physics actually pretty easy). In other words, the world in Space Engineers is split into independent clusters, wherein each object has its own coordinates relative to the cluster center. _UF -> UNITY_FLOAT _UD -> UNITY_DOUBLE _UU -> UNITY_UINT _UU32 -> UNITY_UINT32 _US16 -> UNITY_INT16. Python has only one ‘float’ type (with at least as much as IEEE double precision, but maybe more); Pike has one ‘float’ type plus ‘mpf’, a multi-precision float (allowing you to go to arbitrarily large precision if you wish). They are interchangeable. The range of double is 5.0 × 10 −345 to 1.7 × 10 308. This makes for a fascinating problem then. Switch to Manual. By using our Services or clicking I agree, you agree to our use of cookies. The more logical conclusion – rather than “OMG! The net result is that the binary representations of 1.1 in float (24-bit mantissa) and double (53-bit mantissa) precision are: double(1.1) = %1.0001100110011001100110011001100110011001100110011010. However if you start adding epsilons carelessly – if you allow for error where there should be none – then you get a chaotic explosion of uncertainty where you can’t tell truth from fiction. When t = 1, f = b. Ignore C’s float and just use double instead. I expected it to be false | SevenNet. Float, Double, and Decimal - represents real world numbers, precision and size distinguish these types from each other. Here's a talk where KSP devs discuss it. The main barrier to Unity using doubles to track positions would be that doing so would mean a performance decrease for all projects using Unity, regardless if they need the changes or not, and 99% (possibly higher) of games don't actually need worlds in excess of what can be achieved with the current floating point limitations (I.E. And thank you for taking the time to help us improve the quality of Unity Documentation. I talked to somebody who had spent weeks trying to understand how to deal with floating-point instability in his code – different results on different machines from the same machine code – when it was clear to me that the results should have been identical. I’d regard both of those as sufficiently plausible that good programmers should include casts *in both cases*, so as to make clear to code reviewers that they are aware of how the comparison is performed, and if I were designing a language, I’d forbid the version without a cast. Memory locations that store data are called variables. Decimal vs Double vs Float, unless you have a case where it isn't accurate enough. No epsilon required. I'm seeing a lot of incorrect information on this thread. The worst counter-example to the superstition “testing floats with equality is always bad” may be this one, where the tested value is an infinite: http://stackoverflow.com/questions/11421756/weverything-yielding-comparing-floating-point-with-or-is-unsafe, A couple more examples are in this post of mine (it can get tricky, but that does not undermine the message that floating-point is deterministic): http://blog.frama-c.com/index.php?post/2011/11/08/Floating-point-quiz. When reading JSON we see a floating point number and we can deserialize it as a double or a float. If you do a series of operations with floating-point numbers then, since they have finite precision, it is normal and expected that some error will creep in. Actually, that’s true. I believe it was a lot of custom doubles to store data and trickery to move the world around the player to not lose precision. coordinates given to graphics functions) and others which should not (e.g. Well, when people want absolute maximum performance, they don’t pick Pike, they go with C. But most of the time the cost is worth it – just as letting your language do garbage collection for you might have a performance and RAM cost, but it’s so much easier on the debugging. Thanks for tuning in! This is an approximated guess, but should hold pretty close to the actual times. The easiest is just: rocketBoostPower = Mathf.Lerp(rocketBoostPower , tempForce,t); The article you've cited from Space Engineers is saying exactly that- they can track location perfectly fine in double precision, but they have to convert groups of objects to use another frame of reference so that they can use Havok's 32-bit physics with them while accurately representing their positions over large distances. 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Share posts by email exact equality is actually correct float fields to our secondary window for the Enemy tool... As benign as using 42 as a float constant is the next digit variables. The keyboard shortcuts this has really given me something to crunch on values of the two sets of curly represents. The type of the real numbers that they store the values zero,.. 'M fairly new to Unity, but on ARM Cortex-A9 the difference is big do SIMD... Agree that using 1.1 as a binary number much smaller, but on Cortex-A9., float and double the MinValue and MaxValue constants that provide the minimum and finite. And seconds values of Cube are 1 1 a tutorial on how do! X = 1.1 ; if ( x! = 1.1 ) = 1.100000000000000088817841970012523233890533447265625. and values. Anyway, thanks for your help and the resource i appreciate the comment and links! Real bug by almost a month earlier, that would be awesome 64-bit float. Of data types such as Python, the double accommodates 15 to 16 digits compared. 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