Comment by rafa

Thank you so much for taking the time to dig into the code and docs, it means so much to me!

Here’s the core idea behind how SHDL compiles to C.

At compile time, SHDL groups all gates of the same typea together and packs them into uint64_t bitfields. Each individual gate occupies exactly one bit. If there are more than 64 gates of a given type, multiple uint64_t's are used.

So for example, if a circuit contains: 36 XOR gates - 82 AND gates - 1 NOT gate

The compiler will generate: 1 uint64_t for XOR (36 bits used, rest unused) - 2 uint64_t's for AND (64 + 18 bits) - 1 uint64_t for NOT

Each of these integers represents the state of all gates of that type at once.

The generated C code then works lane-wise: during `tick()`, it computes the inputs for all gates of a given type simultaneously using bitwise operations, and then evaluates them in parallel. Because everything is packed, a single ~, &, |, or ^ operates on up to 64 gates at once.

So instead of iterating gate-by-gate, the simulation step becomes something like: build input bitmasks - apply one bitwise operation per gate type - write the result back into the packed state

In other words, a full simulation step can advance dozens or hundreds of gates using just a handful of native CPU instructions. That’s the main reason the generated C code is both simple and fast.

This also ties directly into the “anti-abstraction” idea sunce there’s no hidden scheduler, no opaque simulator loop, and no dynamic dispatch. The DSL maps very explicitly to bit-level operations in C, and you can see exactly how a logical structure becomes executable code.

The final result is a compiled C shared library, which we can interact from using python (or anything else if you want to build it)

I really appreciate you calling this out. Do you think I should make it clearer in the docs? Thanks again for the comment!

Very cool, I enjoyed the explanation about how bitwise operations are built up to work on a set of gates all at once. I was browsing more of the codebase, it's really well-organized and commented code. I like how SHDL is readable for beginners, the examples are all intuitive and self-explanatory.

As another commenter mentioned, integrating visual diagrams would add an interesting dimension. I saw some manually written ASCII diagrams on the documentation site, and could imagine a way to convert SHDL into diagrams. And a step further, a code playground to write and run SHDL circuits, to be able to see the circuits work visually.

For educational purposes, the docs could use more visual descriptions, like starting with the simplest circuits and show step by step what happens.

Comment by rafa_rrayes