4 ms·

Very few applications need "big" (in this case: > 2^53) integers. So far, I only needed them once. I ported a big int micro benchmark a few months ago. Kinda m

• kevingadd 13y ago
  That's simply not true. There are a ton of applications out there that need true 64-bit integers, not 53-bit integers. Games, crypto, graphics, etc are all fields where you can end up needing 64 bits of integral precision (if not more!) And this isn't based on 'I've only hit one case where I needed them'; this is based on how many users of compilers like Emscripten and JSIL actively utilize 64-bit arithmetic - sometimes they use it so much that they demand high performance! A half-assed implementation that relies on doubles being 'good enough' is just not going to cut it.
  • prewett 13y ago
    Ok, you've got me really curious what these applications are. 2^53 is 3.67e18, which is about 500 times larger than the number of millimeters from the sun to Pluto's maximum orbit [1] allowing an accurate model of a solar system. It is more kilometers than the diameter of the Milky Way [2], allowing accurate models of a galaxy (given the size of stars, 1 km is pretty accurate). I'm guessing that the 15 TB storage requirement of 400 billion stars [3] is going to be a problem long before the integer precision. So I'm not really seeing how games or graphics are going to need more than this precision... Crypto needs 256 bit integers minimum, so 64 bit integers are usually convenient multiples, but not terribly helpful. I'm not saying that 53-bit integers are good enough (although I certainly have never needed anything that large); I have no idea. But I don't see a huge number of applications that obviously need them. So I'm curious... [1] According to http://en.wikipedia.org/wiki/Pluto http://en.wikipedia.org/wiki/Pluto, Pluto's maximum orbit is 7.31e9 km = 7.31e15 mm [2] 120,000 ly = 120,000 ly * 9.5e15 m = 1.14e20 m = 1.14e18 m (http://en.wikipedia.org/wiki/Milky_Way http://en.wikipedia.org/wiki/Milky_Way) [3] Each stars needs (x, y, z) and (v_x, v_y, v_z), probably also in 53-bit integers, so that is 6 * 53 bits = 318 bits = 40 bytes. 4e11 stars * 40 bytes = 1.6e13 bytes = approximately 14.6 TB.
    • demallien 13y ago
      Ok, I can think straight up of one huge use case. With 64 bit integers, I can blend all four colour channels of a pixel in one hit. For graphics operations this is a huge performance boost. (For those unfamiliar with the concept, you allocate 16 bits of the integer to each of rgba, which are only 8 bit values. The extra 8 bits per channel allows you to handle overflow on operations, which means you can do an op in all four channels simultaneously).
    • kevingadd 13y ago
      If you think 'modelling the entire milky way' is an average use case you don't know very much about graphics or game engines, and you should stop extrapolating based on your horribly inadequate knowledge in order to draw faulty conclusions. Again, I have end-users building games and other types of software that are using 64-bit integers right now and have told me they actually need 64 bits of precision. In one case they were actually using pairs of 64-bit integers for 128 bits of precision. For your contrived galaxy example, one thing you need to realize is that value ranges aren't the only thing that matters; value precision is just important, and variable precision is an absolute trainwreck in game development scenarios because it means that your game's physics are nondeterministic (due to precision variance depending on where you are). This is a real problem that affects real games. EVE Online happens to simulate a massive galaxy and massive solar systems, and it uses integers to represent coordinates precisely for this reason. So crypto needs '256 bit integers' (why 256? why not 512? 2048? 4096?), thus it's okay that dart only offers 53 bits of integer precision, and somehow 64 bits wouldn't be better? Does your CPU have 256-bit integer registers? Last I checked, most integer registers only go up to 64 or 128 bits, and the registers bigger than that are for SIMD - i.e. they contain multiple integers, not one big one. I'm not even demanding that Dart implement arbitrary-precision integer arithmetic here - just actually get 64 bit integer arithmetic right, since VIRTUALLY EVERY real programming environment's VM offers it natively to begin with [0]. If you still insist that nothing less than arbitrary precision integer values are sufficient for crypto, then fine - what about 64-bit hashing algorithms (real; used in production)? What about applications that need to do I/O against files/buffers larger than 4GB? What about applications that need to do graphics rendering against image surfaces larger than 4GB? What about audio editing software that needs to operate on long audio recordings larger than 4GB? When 32-bit unix timestamps overflow in 2036, will 64-bit integers still be unimportant? These are all real use cases. If you ignore them all and still argue that 64 bit integers don't matter, you don't seem to have the ability to imagine software beyond your experience. [0] Yes, there are a few scripting runtimes without 64-bit integer values built-in. They are all insufficient for anything resembling numeric computation.