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wrigby commented on Prime Number Grid   susam.net/primegrid.html... · Posted by u/todsacerdoti
fendy3002 · 10 days ago
it's interesting that for 6 cols only the 1st and 5th column has value, ignoring first row.
wrigby · 10 days ago
I enjoyed looking at this one too - playing around for a minute on paper with it was fun.

The numbers in each row (when cols is set to 6) are of the form:

6n+1, 6n+2, 6n+3, 6n+4, 6n+5, and 6n+6

Only 6n+1 and 6n+5 can't be trivially factored:

6n+1, 2(3n+1), 3(2n+1), 2(3n+2), 6n+5, 6(n+1)

So it follows that for any n >= 1, numbers in columns 2, 3, 4, and 6 can never be prime. Fun!

wrigby commented on The Gentoo Perl versioning scheme   wiki.gentoo.org/wiki/Proj... · Posted by u/RGBCube
johnisgood · a month ago
I know, I live in such an European country, but I still know (and use) "." as the decimal point. Most people I know here do, too, and they are not in IT. I think it often depends on context, too, and I would like to think people just know.

I just checked, my bank uses "." as the decimal point, too, instead of the official ",".

wrigby · a month ago
Hah - there I go acting like I know more about Europe than a European. TIL!
wrigby commented on The Gentoo Perl versioning scheme   wiki.gentoo.org/wiki/Proj... · Posted by u/RGBCube
johnisgood · a month ago
50.000 EUR is exactly 50 EUR, though. 50,000 EUR is not.

For the record, before you down-vote, check the other comments. I am from an European country where we "officially" use "," as the decimal point (so yes, I know it might not be universally true, at least not in theory), yet my bank uses ".", and so do people (many, at least). In IT, it always has been ".", too. Of course in elementary school (>20 years ago) we used "," as the decimal point, FWIW. :P It might still be the practice there.

wrigby · a month ago
Most European countries use . as the thousands separator and , as the decimal point.
wrigby commented on Nano-engineered thermoelectrics enable scalable, compressor-free cooling   jhuapl.edu/news/news-rele... · Posted by u/mcswell
bigattichouse · 2 months ago
A lot of people throw around 5% efficiency for Peltiers, and it's just not true - it depends heavily on the temperature differential and current vs. IMax. You can (with care) drive them >2.0 COP.

This isn't anything like a compressor or heatpump system, but Peltiers get a bad rap... they move heat really well if you're not pushing them to the edge.

Here's a nice chart. At 10k difference and 0.1 current max, you're over 2.5 COP. https://www.meerstetter.ch/customer-center/compendium/71-pel...

wrigby · 2 months ago
I didn’t know this, and it jumps out to me because 10k is pretty much the exact difference between room temperature and wine fridge tenperature - I wonder if this is actually not a horrible application for peltiers?
wrigby commented on Plastic bag bans and fees reduce harmful bag litter on shorelines   science.org/doi/10.1126/s... · Posted by u/miles
hansvm · 2 months ago
Coming from an assumption of being overweight or otherwise needing extra exercise in your day the argument completely falls apart. In the US, on average, you'd have a ton of benefits encouraging more walking, likely reducing net CO2-equivalent production in the process (smaller bodies require less maintenance energy).

In a country like Vietnam or Japan (or when applied at an individual level rather than a societal level, each individual weighing whether they actuall need more exercise at the moment) we can get back to the simple assumption of walking requiring extra calories (which you'll eventually eat due to hunger and some sort of weight homeostasis) and just running the numbers (all slightly conservative for "typical" scenarios, favoring beef over gasoline to mildly steelman the argument):

- Beef produces something like 48 lbs of CO2 equivalent emissions per pound

- Beef is something like 1200 calories per pound

- Walking burns something like 90 calories per mile

This directly gives 3.6lb of CO2 equivalent emissions per mile. Under a homeostasis assumption, none is sequestered on average long-term in the person doing the walking, though actual emissions could be slightly higher or lower when taking into account the relative greenhouse impact of human emissions in response to that digestion/exercise (but this is somewhat negligible compared to a cow's methane production).

Even pretty crappy cars in city driving conditions can achieve 20mpg, which is only 1.02lb of CO2 equivalent emissions per mile, 3.5x better.

Most people aren't eating pure beef, but the break-even point (compared to that hypothetical extremely shitty car; the argument favors gasoline even more with more modern vehicles) is 28% of your calorie budget (assuming all other inputs have zero greenhouse impact).

Chicken is better at only 1.6lb of emissions per mile of walking, with a break-even point at 63%. Cheese and butter are _slightly_ better still. Nearly all animal products are much worse than gasoline, and basically any diet made from >=70% animal products (denominated in calories) will have higher emissions than a 20mpg car and driving habit.

If you compare it to more typical cars (my car is dirt cheap, from 2008, and still gets 30mpg city even after 17 years of wear and tear), the break-even point is much worse.

Counter-arguments include that the carbon impact of a car is much higher than just its gasoline consumption, but if you work through the math everything else put together is a rounding error compared to the gas over the lifetime of a vehicle (still 5-15%, but it doesn't substantially impact anything I've said so far).

wrigby · 2 months ago
I was curious what these numbers look like if people get their extra calories from carbs instead of animal products:

- A 100g cooked serving of pasta has 131 calories [1] - This random website claims that a 100g serving of pasta generates 0.58 lb CO2 equivalent emissions - To get 90 calories we need ~69g of pasta - This gives 0.4lb CO2e per mile when walking under pasta power

I'm not sure if the CO2 estimation for pasta is using a cooked weight or a dry weight, so I chose the worst-case scenario. If that CO2e number is applied to 100g of _dry_ pasta, the numbers get way better.

1: https://fdc.nal.usda.gov/food-details/169728/nutrients 2: https://www.co2everything.com/co2e-of/pasta

wrigby commented on SSHTron: A multiplayer lightcycle game that runs through SSH   github.com/zachlatta/ssht... · Posted by u/thunderbong
beloch · 2 months ago
This made me nostalgic for GLTron. After a round of that, I decided to look for a more up-to-date lightcycle game but, surprisingly, there aren't any that capture the look of the 80's Tron movie with a similar level of faithfulness.

Armagetron was roughly contemporary with GLTron, but has a zoomed out perspective that doesn't capture the claustrophobic feeling of not knowing what's on the other side of that trail you're next to. There are also games based on the lightcycle sequences from the newer TRON movies. I have nothing against them, but they're not the same thing.

Seems like an underserved audience might possibly exist for this sort of thing.

wrigby · 2 months ago
This brought back memories - GLTron was fantastic. It was always either that or TuxRacer that would get fired up after finally getting my ATI drivers sorted out on whatever distro I was playing with at the time.

Looks like the last release was in 2016, which is a lot more recent than I expected. I wonder if we could dust it off and get a build?

wrigby commented on Espressif's ESP32-C5 Is Now in Mass Production   espressif.com/en/news/ESP... · Posted by u/radeeyate
mort96 · 4 months ago
Why is 5GHz increasingly important? For most IoT applications, isn't the better wall penetration of 2.4GHz more important than the increased peak speeds of 5GHz?
wrigby · 4 months ago
Yes and no, depending on the environment. In an apartment building, the wall penetration is a liability, as the 2.4ghz spectrum, with only three channels, gets extremely congested. Going 5ghz helps immensely, with more channels available and less penetration, so you get more spectrum reuse.
wrigby commented on Why Apple's Severance gets edited over remote desktop software   tedium.co/2025/03/29/seve... · Posted by u/shortformblog
brcmthrowaway · 5 months ago
Sadly seems to be NVIDIA/PC? only.
wrigby · 5 months ago
This bummed me out, but it looks like it's not? From the Sunshine (server) GitHub page[1]:

  Sunshine is a self-hosted game stream host for Moonlight. Offering low latency, cloud gaming server capabilities with support for AMD, Intel, and Nvidia GPUs for hardware encoding. Software encoding is also available.
1: https://github.com/LizardByte/Sunshine

wrigby commented on Egg prices are soaring. Are backyard chickens the answer?   civileats.com/2025/02/18/... · Posted by u/greenie_beans
latexr · 6 months ago
Mushrooms are “fruits”. The “plant” itself is the mycelium underground and the mushroom is the “fruity” part which is produced to spread the “seeds” (spores).

And fruits are broader than most people think. Many of the things you think as vegetables are fruits: pumpkins, zucchinis, tomatoes. But even outside fruits there is food you can harvest without harming the plant, like potatoes. And we haven’t even gotten into seeds and grains, like rice.

So you can definitely live without killing what you eat.

wrigby · 6 months ago
Hah of course you're 100% right on mushrooms - that totally slipped my mind. Am I completely out to lunch on root vegetables though?
wrigby commented on Egg prices are soaring. Are backyard chickens the answer?   civileats.com/2025/02/18/... · Posted by u/greenie_beans
latexr · 6 months ago
> being vegetarian doesn't exclude you from the necessity of killing in order to live. You're just killing forms of life that you emphasize with less, which is very reasonable and rational but also not materially different.

That’s like saying you kill chickens to eat eggs. You don’t kill a plant to eat its fruit. In fact, plants benefit from animals eating what they produce, be it oranges or tomatoes or something else and crapping the seeds somewhere else for proliferation.

wrigby · 6 months ago
Admittedly this is pedantry on my part, but isn’t this only true for fruits? GP’s argument seems perfectly valid for e.g. carrots or mushrooms.

u/wrigby

KarmaCake day779October 14, 2014
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Systems engineer ("DevOps" if you're a recruiter), with a dash of audio engineer thrown in there for fun.

[ my public key: https://keybase.io/wrigby; my proof: https://keybase.io/wrigby/sigs/MdiYCR9-ieNbkrRSq38cl5kTsYb0FPgkJhNFC0C0ZWA ]

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