The biggest run classified nuclear stockpile loads, at least in the US. They cost about half a billion apiece. And are 30 (carefully cooled and cabled) megawatts. https://en.wikipedia.org/wiki/El_Capitan_(supercomputer)

No chance they're going to take risks to share that hardware with anyone given what it does.

The scaled down version of El Capitan is used for non-classified workloads, some of which are proprietary, like drug simulation. It is called Tuolumne. Not long ago, it was nevertheless still a top ten supercomputer.

Like OP, I also don't see why a government supercomputer does it better than hyperscalers, coreweave, neoclouds, et al, who have put in a ton of capital as even compared to government. For loads where institutional continuity is extremely important, like weather -- and maybe one day, a public LLM model or three -- maybe. But we're not there yet, and there's so much competition in LLM infrastructure that it's quite likely some of these entrants will be bag holders, not a world of juicy margins at all...rather, playing chicken with negative gross margins.

>The big ones are running weather, astronomy simulations, nuclear explosions, biological sequencing, and so on.

these things constitute public goods that benefit the individual regardless of participation.

Many more people materially benefit from e.g. good weather forecasts than form video slop generation.

What's the democratic control of existing resources? I would make the opposite assumption, it would be captured by the wealthiest interests.

Certainly! Your congress representatives would be voting on how to allocate its computing power. (Do you remember who did you vote for last time?)

There are arguments aplenty that schooling and a minimum amount of healthcare are public goods, as are roads built on public land (the government owns most roads after all).

What is the justification for considering data centers capable of running LLMs to be a public good?

There are many counter examples of things many people use but are still private. Clothing stores, restaurants and grocery stores, farms, home appliance factories, cell phone factories, laundromats and more.

Healthcare, schools, roads, generative AI. One of these things is not like the others.

I have no idea why you're being downvoted because you're right. The entire point of taxation is to spread the cost among everyone, and since everyone doesn't utilise every government service every tax payer ends up paying for stuff they don't use. That like, the whole point...