HN user

Symmetry

19,396 karma

Robotics software/firmware engineer at Boston Dynamics working on Spot.

My blog: http://hopefullyintersting.blogspot.com/

My not-horribly-impressive github: https://github.com/aclough/ Mostly you might be interested in stealing my dotfiles.

Posts118
Comments6,208
View on HN
newsletter.semianalysis.com 6mo ago

How AI labs are solving the power problem

Symmetry
167pts258
newsletter.semianalysis.com 7mo ago

AWS Trainium3 Deep Dive – A Potential Challenger Approaching

Symmetry
71pts24
github.com 11mo ago

An analysis of AI performance in 2025 Heuristic contest

Symmetry
2pts0
hopefullyintersting.blogspot.com 1y ago

Normalizing Ratings

Symmetry
51pts52
peterwildeford.substack.com 1y ago

Ten Takes on DeepSeek

Symmetry
4pts0
chipsandcheese.com 1y ago

A RISC-V Progress Check: Benchmarking P550 and C910

Symmetry
3pts0
www.jpl.nasa.gov 1y ago

NASA's Perseverance Rover Scientists Find Intriguing Mars Rock

Symmetry
1pts0
www.neonarrative.us 2y ago

An Interview with Scott Alexander

Symmetry
5pts2
danwang.co 2y ago

Dan Wang's 2023 Letter

Symmetry
5pts0
clinic.amazon.com 2y ago

Amazon Clinic

Symmetry
1pts0
www.niskanencenter.org 3y ago

Culture eats policy

Symmetry
183pts61
www.semianalysis.com 3y ago

AMD MI300 – Taming the Hype

Symmetry
2pts0
chipsandcheese.com 3y ago

Loongson’s 3A5000: China’s Best Shot?

Symmetry
2pts0
theoryofconstraints.blogspot.com 3y ago

“Blue Light” creating capacity for nothing (2007)

Symmetry
151pts78
en.wikipedia.org 3y ago

Nocturnal bottleneck

Symmetry
203pts76
warontherocks.com 4y ago

What's wrong with wanting a “human in the loop”?

Symmetry
75pts84
www.vox.com 4y ago

Why experts are terrified of a human-made pandemic and what we can do to stop it

Symmetry
19pts11
www.propublica.org 4y ago

Why Rapid Covid Tests Are So Expensive and Hard to Find in the US

Symmetry
6pts1
en.wikipedia.org 5y ago

Operation Outward: Attacking power lines with balloons in WWII

Symmetry
8pts5
s3.amazonaws.com 5y ago

Outsourcing Failed at Boeing [pdf]

Symmetry
3pts1
fuse.wikichip.org 5y ago

Arm Introduces Its Confidential Compute Architecture

Symmetry
150pts67
www.fda.gov 5y ago

FDA approves rapid at home Covid testing

Symmetry
1pts0
semiaccurate.com 5y ago

Intel lays out a new direction at Unleashed

Symmetry
2pts0
forums.xilinx.com 5y ago

Using ROCm to Program FPGAs

Symmetry
41pts5
secretgeek.github.io 5y ago

This page is a truly naked, brutalist HTML quine

Symmetry
952pts179
www.cnn.com 5y ago

Explosion rocks Beirut, injuring thousands across Lebanese capital

Symmetry
30pts17
quillette.com 6y ago

Covid-19 Superspreader Events in 28 Countries: Critical Patterns and Lessons

Symmetry
237pts146
acoup.blog 6y ago

Why Don't We Use Chemical Weapons Anymore?

Symmetry
4pts0
wiki.lesswrong.com 6y ago

A Human's Guide to Words (2010)

Symmetry
109pts15
www.gwern.net 6y ago

Littlewood’s Law and the global media

Symmetry
49pts9

There actually wasn't any appreciable fallout after the atomic bombs were dropped on Japan. Fallout is mostly generated when a bomb explodes close to the ground so that its neutrons are able to reach and transmute that ground into radioactive isotopes. The bombs dropped on Japan exploded high up to affect as large an area as possible. Many people suffered terribly from the ionizing radiation produced by those bombs, but all that damage was inflicted in the first microseconds immediately after the bombs detonated.

It's unfortunate that we only have one vocabulary for radiation to cover both a 100 uS dose of fallout and a 10 S one. If a quantity of rock drops on someone we have different words like "pebble" and "boulder" that tell us how concerned we should be. I was shocked to learn that "fallout" in the context of a nuclear war could mean something that could cause you to die in hours, not raise your lifetime risk of cancer somewhat.

At the time (the 1950s) evidence from fruit flies was essentially all the evidence there was. But as the article points out we have pretty good data showing it works the same way in humans.

Even before Linear No Threshold was a thing scientists were doing experiments showing that dosing fruit flies with radiation all at once would lead to a highly mutated second generation, but spreading that radiation out over the course of a month wouldn't.

I wish they wouldn't call these "open source" models. The output weights are open but that's more analogous to a binary. The source would be the training data and techniques that went into producing the binary/weights.

"Open weights" is also a term in wide use and accurately tells us what we're getting.

Except for a brief spike during Covid unemployment has been below 5% for a long time which has led to more wage growth for cooks and waiters than for programmers.

In all of human history nobody has ever had a glass of water with literally no arsenic in it, there are trace amounts in every lake, river, and well. Even the ultra-purified water used in bleeding edge semiconductor fabrication has a lot more than 1 atom of arsenic per glass. In the far future humanity might obtain the technology to create water with literally no pollutants in it but that age has yet to arrive.

Starship V3 2 months ago

Not if you first absorb heat with your solar panels. Conservation of energy and all that.

Starship V3 2 months ago

Yeah. I don't have any doubts that this is something that can be done. But doing it cheaply enough to be worth while is the difficult bit. Elon does have reputation for delivering impressive things, but not for finishing them on the deadlines he sets.

Starship V3 2 months ago

Nobody (sane) is talking about putting nuclear reactors on Satellites in close Earth orbit so we don't have to worry about them generating heat. They've got solar panels that move some of the solar energy they absorb to a central location which presents problems in moving the waste heat back out so that spot doesn't get too hot. But that doesn't change the overall equilibrium temperature.

There's been a lot of churn over the years but additions being done in the same timeframe as XORs has been pretty constant. The Pentium 4 double pumped its ALU but both XORs and ADDs could happen in a half cycle latency. The POWER 6 cut the FO4s of latency in stage from 16 to 10 and kept that parity as well. When you need 2 FO4s for latching between stages and 2 to handle clock jitter at high frequencies the difference between what a XOR needs and what an ADD need start looking smaller, particularly when you include the circuitry to move the data and select the instruction. Maybe if we move to asynchronous circuits?

For a 32 bit number you're looking at going from using 256 to ~1800 transistors in the operation itself. A modern core will have roughly 1,000,000,000 transistors. Some of those are for vector operations that aren't involved in a xor or sub, but most of them are for allowing the core to extract more parallelism from the instruction stream. It's really just a dust mote compared to the power reduction you could get by, e.g., targeting a 10 MHz lower clock rate.

There's a structure called a carry-bypass adder[1] that lets you add two numbers in O(√n) time for only O(n) gates. That or a similar structure is what modern CPUs use and they allow you two add two numbers in a single clock cycle which is all you care about from a software perspective.

There are also tree adders which add in O(log(n)) time but use O(n^2) gates if you really need the speed, but AFAIK nobody actually does need to.

[1]https://en.wikipedia.org/wiki/Carry-skip_adder

That's all true, but on any modern x86 processor both the single pair of gates for the xor and the 10 or so for a carry-bypass 64 bit wide subtraction both happen with a single clock cycle of latency so from a programmer's perspective they're the same in that sense. There's still an energy difference but its tiny compared to what even the register file and bypass network for the operation use, let along the OoO structures.

There's only a few grams of hydrogen in the reactor's plasma, it's reaction with oxygen wouldn't be much more exciting than just losing containment. There are engineering challenges that have to be addressed but no worse than the 6 MW research reactor I used to walk by every day to my college classes in the middle of a dense city.

The proliferation risk of someone using the neutron flux to produce an atomic or dirty bomb are real but that exists no matter where it is.

"Any problem in computer science can be solved with another level of indirection...except for the problem of too many levels of indirection."

SAE level 2 is just a bad idea. People can't be expected to carefully monitor a car and take over at a moment's notice when it's doing all the driving. My adaptive cruise control is great and I hope to have a future car where I can zone out while it drives and take over after after a few seconds heads up, but the zone between shouldn't be a valid feature.

If they wanted they could always just double the $/token. They don't seem to be able to keep up with their current demand and that's what companies normally do in that circumstance if they're looking to money grab, no need for the bankshot approach.

"Poison" can also refer to a substance toxic to other animals. We say that chocolate is poisonous to dogs for instance. And a good fraction of Earth's biosphere was killed off by oxygen poisoning in the first of Earth's great mass extinctions.

Also, the dose makes the poison and excess oxygen actually can poison humans. Deep sea divers have to worry about excess oxygen inducing seizures if they mess up their breathing gasses enough. And even 100% oxygen at regular pressure will slowly damage the lungs, something ICUs have to worry about.

Nick Lane had a great book about oxygen, Oxygen, which maybe isn't as good as his book about mitochondria but is well worth reading.

The technical error that caused accidental chain-of-thought supervision in some prior models (including Mythos Preview) was also present during the training of Claude Opus 4.7, affecting 7.8% of episodes.

_>

It's more reproducing than surviving. If the population of some species increases and the number of copies of some allele remains constant we could consider than gene less fit than the other alleles, in the population genetics sense. So it's frequency rather than survival that geneticists look at. But that proves that there are indeed other ways that they could have defined fitness if they wanted to.