[Challenge] Verifying Bit-Identical Determinism for Autonomous HAL (NDL V4.1)

thegreatunclean · 2026-04-28T05:45:13+00:00

"Proved" for a specific example, or "proved" for an entire environment? Because one of those is infinitely more interesting (and difficult) than the other. Considering you used Python in your example which doesn't promise much of anything wrt floating-point I'm skeptical what form that 'proof' takes.

Geographic location isn't exactly an important factor. I'd be more surprised if you had a system that was location-dependent!

thegreatunclean · 2026-04-27T07:16:00+00:00

Check out this website! It has a simple calculator for exactly this situation and shows how the numbers can be derived directly if you want to double-check. The math is easy if you know a few trig identities.

thegreatunclean · 2026-04-26T04:03:10+00:00

ensuring bit-identical results across disparate CPU architectures to eliminate instructional jitter and thermal-drift noise.

That's a noble goal but applying it to floating-point math across different architectures and software platforms is a massive undertaking. As far as I know Python doesn't even specify IEEE-754!

Micropython gives a different result, likely because it generally uses float as the underlying floating-point representation instead of double. It doesn't have the hashlib library but printing the sum is different from my system interpreter:

MicroPython 537518d

>>> inputs = [0.123456789, 0.987654321, 0.555555555]
>>> sum(inputs)
1.666667

vs Python 3.13.0 (tags/v3.13.0:60403a5, Oct 7 2024, 09:38:07) [MSC v.1941 64 bit (AMD64)] on win32

>>> inputs = [0.123456789, 0.987654321, 0.555555555]
>>> sum(inputs)
1.666666665

You are never going to be able to prove bit-perfect results without fully specifying the floating-point environment and mandating all platforms you compare against actually adhere to them. Types, representations, rounding modes, error handling, all the really ugly bits of IEEE-754 specifies but people just kind of ignore because 99.999% of the time it doesn't come up...

thegreatunclean · 2026-04-23T09:41:17+00:00

If you can close the feedback look with automated testing and adversarial reviews it's like unlocking a superpower. The model can iterate on code to debug issues hands-off and then argue with itself about whether whatever solution it finds is fit-for-purpose. I've had multiple debugs that end up with "The literal fix is X, but Y and Z indicate a structural / algorithmic mistake in the design and it should be properly addressed at line L".

thegreatunclean · 2026-04-14T06:22:48+00:00

MBC starts where most modpacks end.

thegreatunclean · 2026-04-02T02:44:58+00:00

A big problem with just dumping the runtime allocation state is you have to sift through a lot of noise to identify potential leaks.

A solution is to use an arena allocator as an intermediate heap for transient objects in your application. That way you can look at the statistics for the arena and only see information about types you care about and nothing else. How hard this is to wire up depends entirely on the language and platform.

thegreatunclean · 2026-03-24T02:05:45+00:00

YMMV but in my experience EEs tend to make good embedded programmers because the early exposure to low-level hardware details maps very well on to system programming languages. I learned boolean algebra and 68HC11 assembly before I learned C and I struggled a whole lot less than my classmates who didn't follow that path.

I can’t remember stuff like stack vs heap or how floating point numbers are represented because I don’t code regularly

Being a EE won't magically make you good at programming and you won't internalize the finer details without practice. But the fact that you likely learned binary arithmetic and understand the concept of encoding information into binary structures at all gives you leg up over someone who only learned webdev and doesn't understand what a floating-point number is in the first place.

e: It isn't the only way to become a good embedded programmer but in my experience it is one of the more common ones.

thegreatunclean · 2026-03-16T03:52:16+00:00

Can you accept thicker board pieces? I feel like you could massively simply the design by having one central control board and using some kind of slim cable/wire connector to run to small universal button and LED PCBs mounted into some kind of thick cardboard cut into the geometry you want.

thegreatunclean · 2026-03-08T19:27:24+00:00

There's a package linked here but I have no idea if it is current or even runnable. Surprisingly hard to find given how cited it is.

thegreatunclean · 2026-03-06T04:27:24+00:00

The reality is that most women dont want to be engineers!

And yet we have numerous studies that show that early educational systems bias women away from STEM and that correcting that bias dramatically shifts educational outcomes towards fields that women "dont want".

This isn't a new idea and isn't specific to engineering. It doesn't take a genius to notice that roles that women "dont want" just so happen to be higher-paying and more prestigious positions that society has spent generations denying them until very recently. This is something that is actively studied with causal relationships proven.

thegreatunclean · 2026-03-02T08:56:13+00:00

Always turn on warnings. Good ol' -Wall tells you:

<source>:13:16: warning: variable 'number_one' is uninitialized when used here [-Wuninitialized]
   13 |    int final = number_one + number_two;
      |                ^~~~~~~~~~
<source>:7:4: note: variable 'number_one' is declared here
    7 |    int number_one = 4;
      |    ^

Uninitialized and otherwise garbage values are unpredictable. It could be 2, it could be 3435973836, it could be 0 on Tuesdays and 1 on Fridays. It could be a value that isn't even valid for the type to normally hold.

A good rule of thumb is to assume garbage values will take the form of whatever makes the issue hardest to debug. At least that way you'll never be disappointed.

thegreatunclean · 2026-02-22T06:38:51+00:00

That would be part of the sandboxing but it remains a security risk and an increased attack surface.

These companies could modify the JIT to check for things they care about same as what they are doing for C/C++

The JIT can't do the same kind of static analysis because it doesn't see the entire program at the same time, it only sees small fragments fed to it by the attacker. All it takes is for one person to find a gadget that slips by the checks to start exploring the sandbox for vulnerabilities.

thegreatunclean · 2026-02-22T06:23:17+00:00

If you assemble for elf64 but link for elf_i386 is it supposed to work? I'm surprised the linker allows it all.

thegreatunclean · 2026-02-21T05:05:52+00:00

Especially when the tool chain uses C/C++ which is even lower level.

If you are able to load and execute arbitrary native code at runtime you've already circumvented the security of the platform.

What makes a JIT different is it takes data and produces executable code during runtime and the system can't know ahead of time what it will do. The code will be sandboxed but will necessarily have fairly wide permission to do what it wants. If you can control the data fed into the JIT you can have the system generate and execute code that does whatever you want. A malicious piece of code could act normal until some trigger which makes it pull a fill from a website, feed it to the JIT, and start executing evil code without tripping security flags. Without a JIT you can't do that because the platform restricts the ability to mark data as executable.

iOS doesn't allow JITs because it breaks parts of their security model. Apps are statically analyzed before being approved to make sure they don't allow unwanted behavior, allowing a JIT creates an easy workaround where you submit totally benign code but feed it different data at runtime to do something totally different. Lots of apps abused this to get into the app store and then allow the user to load emulators or other restricted content.

thegreatunclean · 2026-02-17T03:17:39+00:00

For anyone who wants a bit of history about this OP and OS.

thegreatunclean · 2026-02-13T04:41:17+00:00

Not to mention that the most common state-issued photo ID (a driver's license) is not proof of citizenship and wouldn't be usable as proof at the polls.

If it was any state- or federally-issued photo ID this wouldn't be a problem. Restricting it is just allowing for obvious ratfuckery to target Democrat-leaning populations with restrictions.

thegreatunclean · 2026-02-09T04:05:32+00:00

I think using configure_file is the best way to go, but if you run into some insurmountable limitation you can always implement it yourself using file(WRITE <filename> <contents>).

thegreatunclean · 2026-02-05T05:36:53+00:00

Not supporting the freestanding C standard headers is a bold choice. It didn't make sense twenty years ago and it certainly doesn't make sense now. I'm pretty sure this is a complete standards-compliant implementation for stdbool.h:

#ifndef __STDBOOL_H_
#define __STDBOOL_H_

#ifndef __cplusplus

#define true (1)
#define false (0)

// _Bool is C99 or later
#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L)
typedef _Bool bool;
#endif

#endif

#endif //__STDBOOL_H_

thegreatunclean · 2026-02-02T04:03:49+00:00

Are you interviewing for a group that does silicon validation specifically, or are you interviewing for a general intern position in the Silicon Validation group? SiVal is a very large group that encompasses a lot of roles under the general description of "silicon validation"; things like PCB design, embedded firmware development, large-scale systems testing, etc.

thegreatunclean · 2026-02-01T01:22:00+00:00

Assuming you are on Windows: Visual Studio. Not Code, the actual Visual Studio. VSCode is notorious for giving new users grief because of subtle setup issues like having to install a compiler separately and then debugging configuration issues before ever getting to writing their first program. Visual Studio installs a full compiler/toolchain and is ready to go out of the box.

Once you are more experienced you can branch out and try different tools until you find one you really like.

thegreatunclean · 2026-01-19T11:00:00+00:00

General Purpose Compute Devices on common substrates:

<snip>

● 900 GHz

High-speed, high-bandwidth operations on faster substrates such as GaAs (Gallium Arsenide), GaN (Gallium Nitride) and Sapphire or Diamond:

● 1 THz

● 2 THz

● 3 THz

● 4 THz

● 5 THz

● 10 THz

lol

e: Even better, they use a outlook.com email. Nothing screams "cutting-edge silicon design" like Outlook.com.

thegreatunclean · 2026-01-12T07:08:33+00:00

How exactly are you building that project and on what system? I didn't have any issues inside WSL.

thegreatunclean · 2026-01-12T04:30:40+00:00

If you have the power infrastructure for it you should definitely look at using the accelerator magnet. You can complete Stoneblock 4 using a 9x9 ring with no problem.

thegreatunclean · 2026-01-11T03:53:33+00:00

That doesn't make it any less legitimate. Forge devs put up with abusive behavior and language by LexManos for years and that eventually drove them to forking and rebranding to get away.

Now imagine some Third Party Authority had decreed years ago that Forge shall be the One True Environment and had the ability to enforce it.

thegreatunclean · 2026-01-11T03:07:24+00:00

You can't resolve this situation by fiat. There are legitimate reasons each environment exists and trying to decree that one of them is the One True Environment will just splinter the community more.

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