How exactly is this a foundational principle of computer science?

When I went through such a selection process years ago, we took all sorts of tests before and even after the selection process. Towards the end, the head instructor told us they don't really have a good way to measure who will make it through. What he did tell us though is that top physical fitness test scores were not indicative that a candidate will make it to the end.

Is there a PDF version or instructions for building your thesis? I'd like to read it.

FWIW, constructing a weapon with highly enriched uranium is, relatively, simple. At the time, the choice was made to use a gun-type weapon that shot a projectile of highly enriched uranium into a a "target" of highly enriched uranium. The scientists were so sure it would work that the design didn't necessitate a live test. This was "little boy", which was eventually dropped on Hiroshima.

Fat Man utilized plutonium which required an implosion to compress the fissile material that would set off the chain reaction. This is a much more complex undertaking, but it's much more efficient. Namely, you need much less fissile material, and more of that fissile material is able to participate in the chain reaction. This design is what allows for nuclear tipped missiles. The same principles can be applied to a U-235 based weapon as well.

The implosion based design is super interesting to read about. One memorable aspect is that the designers realized that applying a tamper of uranium (U-238) around the fissile material allows for significant improvement in yield. The chain reaction is exponential, so the few extra nanoseconds that the uranium keeps the fissile material together leads to significant increase in yield.

https://en.wikipedia.org/wiki/Little_Boy

https://en.wikipedia.org/wiki/Fat_Man

> 11,294 munitions in the first 16 days of the conflict, at a cost of approximately $26 billion.

Several detailed tables are in the link below.

https://www.rusi.org/explore-our-research/publications/comme...

Patriot PAC-3 (~$4M): Nations burnt through 600-800 in the first few days of Operation Epic Fury. There are reports that they're being used for drone defense.

SM-3 (~$10-30M): Ship-launched

SM-6 (~$4-5M): Ship-launched

THAAD (~$12-15M): Terminal phase, high altitude

GBI (~$75M): intended for interception of ICBMs (reported as the hardest type of missile to intercept)

Each type of interceptor is optimal for certain type of threats, which is yet another constraint on the optimization problem.

[0] https://en.wikipedia.org/wiki/Golden_Dome_(missile_defense_s...

Author here. Thank you for your insight.

I took some time to read about the recently proposed "Golden Dome" defense system, and what you laid out seems to be the end goal [0]. It's difficult to tell how realistic this actually is. The size of the constellation of satellites needed seems prohibitive, to say the least.

[0] https://armscontrolcenter.org/fact-sheet-golden-dome/

[1] https://www.defenseone.com/ideas/2026/02/space-based-interce...

Comments URL: https://news.ycombinator.com/item?id=47501950

Points: 382

# Comments: 427

Even storing something simple such as an array of complex numbers as a structure of arrays (SoA) rather than an array of structures (AoS) can unlock a lot of optimizations. For example, less permutes/shuffles and more arithmetic instructions.

Depending on how many fields you actually need when you iterate over the data, you prevent cache pollution as well.

Comments URL: https://news.ycombinator.com/item?id=40973938

Points: 2

# Comments: 0

One of the authors of PhastFT here. Thank you for your interest.

We went out of our way to configure FFTW for AVX-512. The Rust bindings don't do it, but the FFTW itself in the benchmark does.

It's worth noting that with FFTW you have to choose between building it for your CPU and making it non-portable, or targeting the lowest common denominator of CPU features so that it runs everywhere but much slower. Meanwhile PhastFT detects the available CPU features at runtime, and will utilize the fastest CPU features without sacrificing portability.

Lastly, we are currently working on support for interleaved format [1]. That should ship in the next release.

[1] https://github.com/QuState/PhastFT/pull/27