mockery · HackerTrans

Can someone shed light on these two steps in the approximation?

  *         since cos(x+y) ~ cos(x) - sin(x)*y
  *                        ~ cos(x) - x*y,

For the first, maybe it's an approximate identity I'd never heard of?

For the second, it seems like it relies on X being small, but in this code... Y might be small enough for sin==identity approximation, but X isn't, is it?

mockery

3년 전discuss

SongTable won’t compile (on any modern compiler) because the number of initializers (36) doesn’t match the declaration (32)

mockery

4년 전discuss

In addition to the sibling comments, one simple opportunity available to a JIT and not AOT is 100% confidence about the target hardware and its capabilities.

For example AOT compilation often has to account for the possibility that the target machine might not have certain instructions - like SSE/AVX vector ops, and emit both SSE and non-SSE versions of a codepath with, say, a branch to pick the appropriate one dynamically.

Whereas a JIT knows what hardware it's running on - it doesn't have to worry about any other CPUs.

mockery

4년 전discuss

Thanks, those are specific requirements I could definitely see WASM struggling to meet.

In my experience in a large+mature enough codebase (particularly one that is already multi-platform, like Postgres appears to be) many of those requirements are wrapped in an abstraction layer to allow targeting new platforms, but some requirements (like memory mapping) could definitely be dealbreakers if the target platform doesn't naturally support them.

This solution still seems awfully complex (and probably not very efficient) but I certainly see why it's probably the "easiest" option.

mockery

4년 전discuss

The first thing to point out is that our implementation isn't pure WASM. We attempted to compile Postgres for WASM directly from source, but it was more complicated that we anticipated.

Crunchy's HN post provided some hints about the approach they took, which was to virtualize a machine in the browser. We pursued this strategy too, settling on v86 which emulates an x86-compatible CPU and hardware in the browser.

I’m out-of-domain but very curious about this part - it seems like a pretty extreme solution with a lot of possible downsides. Does this mean the “just compile native code to WASM” goal is still far off?

mockery

4년 전discuss

The word expert is not being used in the colloquial sense, but in the technical sense of an "Expert System": https://en.wikipedia.org/wiki/Expert_system

mockery

4년 전discuss

So if I make a new, identical copy of a GPL'ed codebase - should I feel free to use it for whatever purpose I want and ignore the GPL?

mockery

4년 전discuss

The full game isn't playable on that page. I believe all three sets of assets (HLDM, Uplink, Hazard Course) are from demos or free products.

Making the full game playable would probably be less OK.

mockery

4년 전discuss

It's totally reasonable to lament duplicated effort, but it's worth pointing out that this particular attempt is from a company[0] whose business is Qt consulting - so it's easy to imagine that they might succeed (due to expertise, size, and motivation) where others have not.

The post also explains why they started from scratch vs. existing approaches - I'm not qualified to evaluate the claims, but I think they deserve some credit for explicitly talking through their reasons.

[0] https://www.kdab.com/

mockery

4년 전discuss

I think GP is reacting to the word "obligation" (I certainly did.)

I'd claim there are actions that may be "morally justifiable" yet not raise to a level that creates a "moral obligation." The word "obligation" implies (to me at least) some sort of guilt or culpability if you don't undertake the action.

In fact my instinct is that most morally justifiable actions aren't weighty enough to be obligations. Consider any "morally neutral" action (for example, eating an apple instead of an orange for a snack) - I would label such an action "morally justifiable" (since applying the rules of morality does not argue against it) but it's certainly not a "moral obligation" (even ignoring the fact that the alternative is also morally justifiable!)

You could perhaps argue there is no such thing as a "truly neutral" action to an omniscient observer, who can measure and predict the impact on total human happiness of any action with certainty. Such an individual would indeed have a much more restrictive set of "morally justifiable" actions available to them - fortunately we mortals aren't burdened with that level of insight or certainty!

mockery

4년 전discuss

Not GP, but the code in the article passes 'unsigned int mutex' by-value, and then operates on its address (which will potentially be at a different stack address on each invocation, and will certainly be different for different threads.) It won't serve its purpose at all.

To my eye, the code is fundamentally broken in a way that's surprising for an article trying to teach threading, and it's likely confuse someone unfamiliar with these concepts.

mockery

4년 전discuss

Perhaps confusingly, the term "immediate mode GUI" usually describes an API style. NOT an implementation detail.

It suggests a particular implementation, but in practice most nontrivial "immediate mode" GUI libraries (including egui [1] and the famous Dear-IMGUI [2] [3] ) retain some "shadow state" between frames. The existence or scope of that state is a (sometimes-leaky) implementation detail that shouldn't distract from the fact that the API presented is still "immediate mode."

[1] https://github.com/emilk/egui#ids

[2] https://github.com/ocornut/imgui/blob/master/docs/FAQ.md#q-a...

[3] https://github.com/ocornut/imgui/wiki/About-the-IMGUI-paradi...

mockery

5년 전discuss

It seems like the brownout should be publicized on the front page of github.com - or at least githubstatus.com ?

(Although I'm not an active git/github user, so maybe there's an even more more obvious place a naive user having issues would go to figure out what their problem is. Hopefully there's a helpful commandline error explaining the situation.)

mockery

5년 전discuss

> Education is insanely overfunded

Can you cite a source for that claim? Genuinely curious, because I don't know if I've ever heard someone suggest it. (Conversely, the idea that education is substantially underfunded is generally assumed - at least in my bubble.)

mockery

5년 전discuss

Variations on the Bridson paper you linked are commonly implemented in games and graphics circles under the name "Curl Noise" - for example Houdini[1] or Unity[2]

Google that term for many examples, but [3] looks like a good starting point.

[1] https://www.sidefx.com/docs/houdini/nodes/vop/curlnoise.html

[2] https://docs.unity3d.com/Packages/com.unity.visualeffectgrap...

[3] http://petewerner.blogspot.com/2015/02/intro-to-curl-noise.h...

mockery

5년 전discuss

Perhaps, but it's quite convenient for any software that wants to ingest PSD files without the (nigh-intractable) challenge of reimplementing the entirety of Photoshop's parser and rendering systems!

mockery

5년 전discuss

Most* PSD files contain a "preview" copy of the fully-flattened document (which is compressed.) Flat white image compresses far better, so that portion of the file doesn't take as much space.

Depending on what your layers look like (how many, how much they cover, etc.) it's not too surprising that the preview image could take a substantial fraction of the total file size (sounds like ~20% in this case!)

* I believe this behavior can be toggled off with an option.

mockery

6년 전discuss

Seems to me like you're tacitly agreeing with GP here - you're just making a claim about which currency system you trust more! (And attempting to convince others of the same position.)

mockery

6년 전discuss

Using GP's definition: "custom" engines -- i.e. engines that are not provided commercially by third parties it's pretty easy to argue Fortnite also uses a "custom" engine. (And that's not pedantry - they obviously have knowledge and access that no licensee could dream of.)

That said, tere are a decent set of AAA games that license Unreal (PUBG, State of Decay, Borderlands series, Arkham series, XCom series) but it's rare among the absolute biggest titles ("AAAA" if you will.)

mockery

6년 전discuss

Yes! The 010 Editor's templating language is a nearly unique (in my experience) hybrid between C-like declarations and imperative flow that's exactly what I want for parsing arbitrary binary files.

The template executes like a script (with conditionals and looping) and a line like "int32 myNum;" is actually just syntactic sugar for "read 4 bytes from the current file pointer and label it myNum." Their example probably does a better job explaining it than I can:

  struct FILE {
      struct HEADER {
   char    type[4];
          int     version;
          ushort  numRecords;
      } header <bgcolor=cLtGray>;
  
      struct RECORD {
          int     employeeId;
          char    name[40];
          float salary;
          if( file.header.version > 1 )
              int      numChildren;
          if( file.header.version > 2 )
              time_t   birthDate;
      } record[ file.header.numRecords ];
  
  } file;

( From: https://www.sweetscape.com/010editor/templates.html )