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David Andersen

@daveandersen.bsky.social
1.3K followers 897 following 3.7K posts

Computer Science Professor, CMU; co-founder and CTO, Enriched Ag Energy-efficient computing, a dash of security, and a pinch of databases. Also on Mastodon (hachyderm.io/@dave_andersen ) signal: dga.48 he/him

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David Andersen @daveandersen.bsky.social · 15h
I don't know what it is about this semester, but I'm leaving my grad class daily being just astoundingly impressed with the students. We may^H^H^Hwill be be facing an AI education crisis or already are, but this crop of students (early Ph.D., MS, a couple of ugrad seniors) still have the juice.
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David Andersen @daveandersen.bsky.social · 21h
Huh. Apparently now I am a professor in the Griffin School of Computer Science. I choose to believe it's a mythology reference. We should rename our competitive programming team or hacking team the LionEagles. www.cmu.edu/news/stories...
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David Andersen @daveandersen.bsky.social · 29/09/2026
It's mine and you can't take it away from me!
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David Andersen @daveandersen.bsky.social · 29/09/2026
Dear puppy with razor sharp teeth, I will WIN THIS BATTLE, with the POWER OF TECHNOLOGY
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Dave DiCello @davedicello.bsky.social · 29/09/2026
So many film images to go through as of late, but I love how this one came out. The way the clouds are reflecting off of PPG Place in #pittsburgh almost look connected with the clouds in front, making for such an interesting view.
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David Andersen @daveandersen.bsky.social · 28/09/2026
Nice thread to read. My colleagues in HCI (human computer interaction) like to point out that not only is none of us (CS people) normal, most people we know aren't either, by proximity to a Ph.D. computer scientist. It's risky to look at ourselves and say "oh, this is surely useful!" 1/
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David Andersen @daveandersen.bsky.social · 27/09/2026
made gougeres to bring to the block party. It turns out there is such a thing as eating too much puff pastry. don't think I'll be making those again for a while. 🤣
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David Andersen @daveandersen.bsky.social · 25/09/2026
well, that was a little harrowing. First bike-car accident I've ever been in in ~45 years of riding a bike all the time. Driver was signaling left and then decided, as I was going past them, to turn right instead.
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David Andersen @daveandersen.bsky.social · 25/09/2026
The phone scammers have defeated me. Five or more calls per hour for multiple hours per day making it through Google fi's spam prevention and many bypassing android phone screen. Time for the nuclear option. Hope nobody needs to call me for a while! 😭
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David Andersen @daveandersen.bsky.social · 21/09/2026
Random blog post inspired by someone else's random blog post. Mostly I just love succinct data structures and continue to want the world to know about them. :-) wiredream.com/vowels/
wiredream.com
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David Andersen @daveandersen.bsky.social · 21/09/2026
Oh @verizonofficial.bsky.social FiOS, I am so unimpressed this week You see, you have one part of an ECMP or LAG group that's flaky right by my house. Why? Because specific 5-tuples consistently have 90% outbound packet loss while most others have 0%. The lcr-21 path is the one with a bad sub-link.
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David Andersen @daveandersen.bsky.social · 21/09/2026
Random blog post inspired by someone else's random blog post. Mostly I just love succinct data structures and continue to want the world to know about them. :-) wiredream.com/vowels/
wiredream.com
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David Andersen @daveandersen.bsky.social · 19/09/2026
Oy. The home improvement scam calls have won. I've switched call screening back to screening all unknown numbers, which I hate, because it has a nontrivial false positive rate. Uncertain why Google fi isn't doing a better job against this wave of them. May a pox befall their entire call center
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David Andersen @daveandersen.bsky.social · 19/09/2026
Year 3 of the 5lb CO2 tank. Only got 11 months out of it this time and the price of the refill went up from $13 to $14, but still a huge win over $17 for a 0.9lb refill with exchange for sodastream’s little co2 thingies. $0.06 / liter of carbonated water vs like $0.40/liter. 🤓
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David Andersen @daveandersen.bsky.social · 19/09/2026
Today, bluesky has the juice
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c0nc0rdance @c0nc0rdance.bsky.social · 17/09/2026
There are two ways you will react to the image below. Never encountered: "Neat! A caterpillar with a little sports jersey on!" Encountered: "Oh god, get it away before it kills us all!" Let's meet the saddleback caterpillar (Acharia stimulea), a tiny bug that that 'hides' a painful sting.
From Brittanica Encyclopedia:
"Saddleback caterpillar
The armed and brightly colored saddleback caterpillar (Acharia stimulea) is a type of slug caterpillar moth found in North America."

CREDIT:  hagit berkovich/Shutterstock.com
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David Andersen @daveandersen.bsky.social · 16/09/2026
I got well-ackshully'd by my watch in class today. I failed to turn off the "talk to Gemini by raising your hand to your mouth" thing. It never works but it triggers sometimes writing on the blackboard. I said "the drive's read head parks" and my watch burst out "THAT IS CALLED THE ACTUATOR" dead
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David Andersen @daveandersen.bsky.social · 16/09/2026
me: llm, implement this new pipeline for training a network I want to play with. llm: Sure! Let me do that! (it does) But you told me not to run from 3-9pm when it's peak power so I'll delay launching it. me: it's 10pm. llm: sure! you can override the local clock. (the local clock says 10pm) 🤦🏼
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David Andersen @daveandersen.bsky.social · 14/09/2026
I ❤️ my cargo e-bike. It's let us stay a 1 car family despite two kids. That might change but so far, 3.4 years in, it's cost us about $2k/year and continues dropping as we amortize the purchase price. I'll take that over $15k/year. 🤓
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David Andersen @daveandersen.bsky.social · 14/09/2026
puppy and i are having the same reaction to monday morning* (* ok, this is only partly true. we're both sleepy but I didn't poop on the floor. yet.)
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Michael Clemens @mclem.org · 12/09/2026
The US President's new proposal to tax international students has been approved by the White House for release this week. It's an unprecedented $100,000 tax on int'l grads who stay to work after graduation on Optional Practical Training (most grads do), a crucial bridge to remaining by any channel.
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David Andersen @daveandersen.bsky.social · 11/09/2026
This was worth reading and thinking about mathandai.org
mathandai.org
Declaration — Math and AI
Read the declaration and add your name.
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David Andersen @daveandersen.bsky.social · 11/09/2026
It amuses me that the easiest way to get the dog crate to my office was to take it on the cargo bike - the university seems to frown on the idea of me parking my car on the sidewalk next to the entrance to the building but they have kindly provided a bike rack there. 🤓
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David Andersen @daveandersen.bsky.social · 08/09/2026
Mistakes were made
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David Andersen @daveandersen.bsky.social · 07/09/2026
i am goose destroyer, hear me roar
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David Andersen @daveandersen.bsky.social · 07/09/2026
Crag puppy's first time climbing went well.
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David Andersen @daveandersen.bsky.social · 07/09/2026
Tryin' out some classic Pittsburgh rock 🤣
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David Andersen @daveandersen.bsky.social · 06/09/2026
I let the garden be taken over by volunteer butternut squash this year, but fortunately, they roasted up very well. Which is good, because there are like five more in there.
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Sundance @sundance.bikesky.social · 19/08/2026
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David Andersen @daveandersen.bsky.social · 04/09/2026
niche AI comment: I used to like Artificial Analysis as a way to quickly eyeball models, but their use of TerminalBench 2.1 is making them useless for what I actually care about. It's saturated. Consider below. Gemini 3.8 "wins" TerminalBench 2.1 but is remarkably behind on 4.0, which ...
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David Andersen @daveandersen.bsky.social · 04/09/2026
Daaaaamn. The intersection at Reynolds and Murtland was flooded three feet deep. Saw someone wading across it and decided to find a better way home from the climbing gym. #pittsburgh
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David Andersen @daveandersen.bsky.social · 03/09/2026
As I watch the current cascading outage across AI providers ("claude is down! let's switch to codex! ... oops"), I can't help but ponder again when it will become important for those companies to balance (a) move-fast-AI culture and; (b) keep-things-running SRE culture. Right now they mostly do (a).
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David Andersen @daveandersen.bsky.social · 02/09/2026
sleeping puppy is best puppy particularly since she's not trying to eat my ankles while asleep.
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David Andersen @daveandersen.bsky.social · 01/09/2026
First attempt at bring your puppy to work day is going pretty well so far, though it took both me + 14yo to manage her effectively through a meeting. :) (Goal is to make sure she's well-socialized to work so that once she's capable of settling more I can bring her regularly.)
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David Andersen @daveandersen.bsky.social · 01/09/2026
😍 www.nber.org/digest/20260... tl;dr: Ambulance time-to-reach-hospital near the congestion pricing boundary in NYC fell from about 12 minutes to 11 minutes (~8%), almost certainly improving patient outcomes. Nice stuff.
nber.org
Urban Congestion Pricing and the Response Times of Emergency Medical Services
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David Andersen @daveandersen.bsky.social · 29/08/2026
Now witness the power of this fully prepped and operational burrito station* *It does not make space laser sounds :(
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disc horse bot @horsedisc.bsky.social · 28/08/2026
Tactical Princess Peach can still happen if people want it bad enough
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David Andersen @daveandersen.bsky.social · 27/08/2026
Puppy day 6: oh thank god, dr. prof. spouse found the stealth poo and got rid of it
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David Andersen @daveandersen.bsky.social · 26/08/2026
Puppy crate training progress as measured by sleeping heart rate patterns. Good progress. That first night was rough.
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David Andersen @daveandersen.bsky.social · 25/08/2026
Oh my god this woman needs to be interviewed more often www.cbc.ca/radio/asitha...
cbc.ca
B.C. swimmer crosses the Strait of Georgia in under nine hours | CBC Radio
When it comes to crossing the Strait of Georgia, most people would choose to do so in a boat, a ship — any kind of a marine vessel, really. But not Melanie Buggey. She chose to swim.
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David Andersen @daveandersen.bsky.social · 25/08/2026
Floppy ear brigade reporting for duty
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Richard Kadrey @richardkadrey.bsky.social · 24/08/2026
The Allegheny River this morning Pittsburgh, PA
a bright day with just a few clouds in the sky looking across the river toward downtown and a bridge whose name I can't remember
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David Andersen @daveandersen.bsky.social · 24/08/2026
Friends with kids at dice: I'm so confused. The text version of the calendar says Jan 21 clerical, Jan 22 professional development days. But the image on that page says Jan 19 clerical, Jan 20 clerical. Anyone know which of these is actually correct or where ground is? www.pghschools.org/calendar
pghschools.org
Calendar - Pittsburgh School District
Pittsburgh Public Schools District Calendar
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David Andersen @daveandersen.bsky.social · 24/08/2026
I love working at a university. ,🤣 (photograph is from today at cmu. This thing is a couple of years old, but I hadn't seen it before..)
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David Andersen @daveandersen.bsky.social · 24/08/2026
Yes, you (admittedly cute) little monster, sleep, sleep, get all of the sleep you didn't get last night while waking me up every 45 minutes.
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David Andersen @daveandersen.bsky.social · 21/08/2026
Oh dear. We seem to have added someone to our family. Nova, meet bluesky.
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David Andersen @daveandersen.bsky.social · 19/08/2026
There's more information needed to dig into this graph from a causal perspective, which would be really useful, but just the fact that AI is so breaking the relationship between homework scores and test scores is itself really painful for education. It's one I'm feeling a lot of for undergrad stuff.
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BWJones @bwjones.bsky.social · 19/08/2026
Many years ago, Salt Lake City Utah did the same experiment with the same results. They took the biggest users of social services and housed them along with resources. It was *cheaper* than not doing that and they had better outcomes.
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David Andersen @daveandersen.bsky.social · 18/08/2026
Decided to treat ourselves a little for our last night in Iceland. Mmmm.
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David Andersen @daveandersen.bsky.social · 17/08/2026
Interesting if you like reading about energy generation pricing and policy: newsletter.semianalysis.com/p/12b-of-us-... (Long and detailed. Perhaps a bit excessively verbose. But it will also make you more annoyed at PJM)
newsletter.semianalysis.com
Full of Cold Air - PJM's $12B modeling mistake
How America's greatest grid wasted billions and is putting ratepayers at risk by using bad models, no not those models.
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