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cjbillington commented on NIST ion clock sets new record for most accurate clock   nist.gov/news-events/news... · Posted by u/voxadam
Avamander · 2 months ago
> It's an amazing time to be alive. While not this precise, you can have atomic cesium beam clocks of your own for a few thousand dollars each, and some elbow grease.

How hard or expensive would it be for a reasonably equipped lab to build their own optical clock though? I see there are optical clocks the size of few rack units on the market for a rather hefty price, are the materials needed that expensive or is it just the expertise?

cjbillington · 2 months ago
The lasers alone set you back many tens of k so it's not really possible to do on the cheap presently, even if a lot of the cost is expertise and the high overhead of R&D costs when only producing small number of units.

Oh and to know if it's any good you have to either build two (ideally more) of them to compare against each other (ideally using different approaches so their errors are less correlated), or have access to a clock better than the one you're building to compare to. So you can rarely get away with building just one if you want to know if you've succeeded.

Source: I work on the software for these portable optical clocks: https://phys.org/news/2025-07-quantum-clocks-accuracy-curren...

cjbillington commented on Nano-engineered thermoelectrics enable scalable, compressor-free cooling   jhuapl.edu/news/news-rele... · Posted by u/mcswell
dvh · 2 months ago
But isn't condensation based cooling like 500% efficient?
cjbillington · 2 months ago
The Carnot limit is the theoretical upper limit of the efficiency of a heat pump, so the stated number is presumably with respect to that, not heat moved per unit energy input like you're quoting.
cjbillington commented on Private sector lost 33k jobs, badly missing expectations of 100k increase   cnbc.com/2025/07/02/adp-j... · Posted by u/ceejayoz
pzo · 2 months ago
> Even the good old GDP per capita covers your case.

GDP or even GDP per capita is not the best metric. You can sell 100 iphones for $1000 or sell 500 cheap androids for $200 and both countries will have same GDP but I think output and outcome is much better in latter case (you produced 5x more products and 5x more people can benefits and be more productive with those 'tools'). Sure iphone for $1000 is better than $200 android phone but is it 5x better? Same with cars you can sell ferrari or more cheaper toyotas for the same value. We would have to measure how much goods we can produce.

cjbillington · 2 months ago
If it's true that more phones will allow people to be more productive, that increase in productivity should show up in GDP as well
cjbillington commented on Melbourne man discovers extensive model train network underneath house   sbs.com.au/news/article/i... · Posted by u/cfcfcf
averageRoyalty · 2 months ago
Population growth rate in Victoria has been 1.9% YOY average for 20 years, with no sign of slowing down. Even if they hit their targets, demand will exceed supply.

The Victorian government has also failed significantly on public housing. The wait time is about 20 months (10 months is VicGov's target, it was 14 months 3 years ago) and they're currently looking to demolish many existing options without many short term optionsnfor residents.

It seems very unlikely to me that Victoria's house prices will drop in any sigificant way this decade.

cjbillington · 2 months ago
I don't think there'll be any significant drop on a sub-decade timescale unless there's some kind of financial crisis, but the ideal kind of trend is prices stagnating or growing slower than wages, which is the case right now - and the question is whether it will continue.

I think there is a good chance it will, as long as a change of government doesn't deliberately dismantle the current approach. Yes there's population growth and yet prices have been stagnant or declining the past few years and construction has picked up. That's a good trend!

I'm not familiar with the situation with public housing but am happy to accept if the government has failed there. But this seems like a separate failure rather than an indictment of their approach to increasing supply generally which I think is working.

cjbillington commented on Melbourne man discovers extensive model train network underneath house   sbs.com.au/news/article/i... · Posted by u/cfcfcf
danielheath · 2 months ago
The Melbourne real-estate market is _mad_. Prices (relative to wages) are exceptionally high and continue to rise, spending half your take-home income on housing isn't super uncommon.

Widespread sentiment that if you don't buy something ASAP, you'll never be able to - meaning lots of buyers skimping on due diligence to close a sale.

cjbillington · 2 months ago
Melbourne property prices actually haven't recovered from their 2022 peak, and that's before adjusting for inflation. I believe rents are down in real terms as well.

Things have been crazy for a long time, but I am actually optimistic for Melbourne specifically - the construction rate is up and the state government has been decreasing the power local governments have to block or delay development. If this continues, housing affordability should improve. My main concern is that a change of government may put an end to it, but I hope not.

Some details about what VIC is doing differently in this AFR article if you're interested (archive link because original is paywalled):

https://archive.md/yeDxF

cjbillington commented on Getting Past Procrastination   spectrum.ieee.org/getting... · Posted by u/WaitWaitWha
diggan · 3 months ago
> The magic of Git means you can immediately find them in the working index

How does git help you find certain texts in files? `grep` should do the trick just fine, unless I misunderstand what "chuck Todo comments in the code" mean, the code lives on your disk no?

cjbillington · 3 months ago
They'll show up in the diff.

Grep will find them too, but any in the diff you'll know for sure were added by you.

cjbillington commented on 20 years of Git   blog.gitbutler.com/20-yea... · Posted by u/videlov
TiredOfLife · 5 months ago
For me it won (10+ years ago) because for some reason git (a deeply linux oriented software) had better Windows support than Mercurial (that boasted about Windows support). You could even add files with names in various writing systems to git. I am not sure that Mercurial can do that even now.
cjbillington · 5 months ago
Huh, that's not my recollection.

Mercurial on windows was "download tortoisehg, use it", whereas git didn't have a good GUI and was full of footguns about line endings and case-insensitivity of branch names and the like.

Nowadays I use sublime merge on Windows and Linux alike and it's fine. Which solves the GUI issue, though the line ending issue is the same as it's always been (it's fine if you remember to just set it to "don't change line endings" globally but you have to remember to do that), and I'm not sure about case insensitivity of branch names.

Pretty sure Mercurial handles arbitrary filenames as UTF-8 encoded bytestrings, whether there was a problem with this in the past I can't recall, but would be very surprised if there was now.

Edit: does seem there at least used to be issues around this:

https://stackoverflow.com/questions/7256708/mercurial-proble...

though google does show at least some results for similar issues with git

cjbillington commented on Show HN: Beating Pokemon Red with RL and <10M Parameters   drubinstein.github.io/pok... · Posted by u/drubs
fancyswimtime · 6 months ago
the game has been beaten by fish
cjbillington · 6 months ago
Based on the other examples of random inputs not being sufficient, I dare say the fish-based attempt may have been fraudulent.
cjbillington commented on A FPGA friendly 32 bit RISC-V CPU implementation   github.com/SpinalHDL/VexR... · Posted by u/_benj
phire · 7 months ago
Most FPGAs have converged on 18 bit wide multiplier blocks. If you ask for a 64 bit multiplier, the router will automatically chain together four multiplier blocks and add them together in a single cycle, which is really going to hurt your maximum clock speed (fmax).

VexRiscv is aware of this unofficial standard, and asks for four 16x64 multiplies and adds the result together on the next cycle. This produces a much better fmax on FPGAs, but if you were targeting an ASIC, you would be better off asking for a 64-bit multiplier, or not trying for a single-cycle multiply.

Most modern CPUs tend to target a 3 cycle pipelined multiplication, which means 22-bit wide multipliers. Doing this on an FPGA each 22-bit multiplication would require two 18-bit multiplier blocks, for a total of six multipliers, wasting more resources.

-----

In general, "FPGA friendly" means optimizing your design to take advantage of the things which are cheap on FPGAs, like the 18-bit wide multipliers and the block ram. Such designs tend to run faster on FPGAs and use less resources, but it's wasteful to synthesize them to ASICs.

cjbillington · 7 months ago
It took me to the end of your comment to realise the crucial bit I was missing: that they're talking about implementing the CPU on an FPGA.

As opposed to, say, interfacing with an FPGA which could be totally different way to be "FPGA-friendly".

cjbillington commented on Starship Flight 7   spacex.com/launches/missi... · Posted by u/chinathrow
einrealist · 7 months ago
Waiting for the day when they can load more than a banana. But I fear, the planet will be uninhabitable before that's a thing.
cjbillington · 7 months ago
They had some Starlink simulators they were planning to deploy (to a suborbital trajectory, to re-enter along with the ship) this launch.

u/cjbillington

KarmaCake day174August 14, 2017View Original