Hacker News: Thorondor

New comment by Thorondor in "Matrix Multiplications on GPUs Run Faster When Given “Predictable” Data (2024)"

Thorondor — Wed, 27 May 2026 19:21:38 +0000

Weights should not be 0 (at least not frequently) but in a ReLU-based neural network, activations are 0 pretty often. You're absolutely right about die area though.

New comment by Thorondor in "Matrix Multiplications on GPUs Run Faster When Given “Predictable” Data (2024)"

Thorondor — Wed, 27 May 2026 17:41:55 +0000

Hardware engineer here. Special casing the multiply by 0 and multiply by 1 paths is harder than it sounds. In software, the cost of adding special cases is simply performance. You're adding more instructions that execute in sequence on a CPU that already physically exists. Doing this for your multiply case is worthwhile because the speedup is large for 0 and 1 while the cost is not that large (relative to the time taken for the whole multiplication operation) for other values.

Hardware is different. Every operation that can be performed in hardware by a chip needs dedicated circuitry. Special casing 0 and 1 means adding at least OR reduction on each operand and a dedicated multiplexer for every bit of the output. Those transistors use power even when they're not in use (leakage power is a huge issue on modern semiconductor processes). They also degrade timing by adding more gates on critical paths through the multipliers. (The timing issue here is that all operations that happen between one flip-flop and another flip-flop need to finish within one clock cycle.) And unless there are whole blocks of 0's and 1's (this does happen in certain neural networks), you typically won't see a direct speedup anyway. In software terms, the matrix multiply is scheduled as many parallel operations that cannot be accelerated much overall by skipping a few operations in some "threads."

All of this makes zero skipping a nontrivial topic. People do still try to do it but it needs serious consideration as, depending on the application, the case is rarely one-sided.

AI agent designs complete RISC-V CPU from a 219-word spec, startup claims

Thorondor — Thu, 23 Apr 2026 13:28:36 +0000

Article URL: https://www.tomshardware.com/tech-industry/artificial-intelligence/ai-agent-designs-a-complete-risc-v-cpu-from-a-219-word-spec-in-just-12-hours

Comments URL: https://news.ycombinator.com/item?id=47875538

Points: 3

# Comments: 0

The Rabbit Woman of Gowanus (2015)

Thorondor — Sun, 01 Mar 2026 23:04:01 +0000

Article URL: https://www.theawl.com/2015/02/the-rabbit-woman-of-gowanus/

Comments URL: https://news.ycombinator.com/item?id=47211712

Points: 3

# Comments: 0

Are laser-based spark plugs a viable option?

Thorondor — Thu, 22 Jan 2026 15:24:56 +0000

Article URL: https://www.eetimes.com/are-laser-based-spark-plugs-a-viable-option-for-igniting-ice-fuel/

Comments URL: https://news.ycombinator.com/item?id=46720463

Points: 1

# Comments: 0

New comment by Thorondor in "Donut Lab’s all-solid-state battery delivers 400 Wh/kg of energy density"

Thorondor — Tue, 06 Jan 2026 02:14:52 +0000

Yes, but a car can't use electricity at 1 MV and converting the megawatt back to something lower than 1 MV still produces a lot of heat.

China's Hongqi Bridge collapse: bridge stood, mountain didn't

Thorondor — Wed, 12 Nov 2025 01:40:11 +0000

Article URL: https://scientificinquirer.com/2025/11/11/hongqi-bridge-collapse-the-bridge-stood-the-mountain-didnt/

Comments URL: https://news.ycombinator.com/item?id=45895421

Points: 19

# Comments: 0

Otto Aerospace Secures 300 Aircraft Order with Flexjet

Thorondor — Tue, 30 Sep 2025 05:36:20 +0000

Article URL: https://ottoaerospace.com/news/otto-aerospace-secures-historic-300-aircraft-order-with-flexjet/

Comments URL: https://news.ycombinator.com/item?id=45422260

Points: 4

# Comments: 0

New comment by Thorondor in "Mirror Life Worries"

Thorondor — Thu, 18 Sep 2025 16:24:26 +0000

A mirror virus would not be able to infect normal cells. Viruses depend on (chiral) host cell machinery such as ribosomes to reproduce.

New comment by Thorondor in "AI-designed chips are so weird that 'humans cannot understand them'"

Thorondor — Mon, 24 Feb 2025 15:23:15 +0000

> Take a look at the structure of something like CMOS and you’ll see why running transistors in anything other than “on” or “off” is definitely not energy efficient. In fact, the transitions are where the energy usage largely goes. We try to get through that transition period as rapidly as possible because minimal current flows when the transistors reach the on or off state.

Sounds like you might be thinking of power electronic circuits rather than CMOS. In a CMOS logic circuit, current does not flow from Vdd to ground as long as either the p-type or the n-type transistor is fully switched off. The circuit under discussion was operated in subthreshold mode, in which one transistor in a complementary pair is partially switched on and the other is fully switched off. So it still only uses power during transitions, and the energy consumed in each transition is lower than in the normal mode because less voltage is switched at the transistor gate.

New comment by Thorondor in "Amplification of electromagnetic fields by a rotating body"

Thorondor — Fri, 18 Oct 2024 02:47:45 +0000

The main issue is that when objects spin really, really fast, they tend to explode due to centrifugal force.

The tensile stress on a spinning round, homogeneous object is p * r^2 * w^2, where p is density, r is radius, and w is angular velocity. Using your numbers for a steel cylinder with density 8 g/cm^3 gives a tensile stress of (8 g/cm^3) * (5 mm)^2 * (2pi*1 MHz)^2 = about 8 TPa which vastly exceeds the tensile strength of steel or any other known material. Using cows connected by ropes would be even worse because the enormous centrifugal force would be borne by only a small rope.

New comment by Thorondor in "The first nuclear clock will test if fundamental constants change"

Thorondor — Thu, 05 Sep 2024 13:40:31 +0000

You're ignoring the units of G. The gravitational constant has units N * m^2 / kg^2 = m^3 / (kg * s^2). That contains a length unit raised to the third power, which exactly balances the factor of 8 that you identified.

New comment by Thorondor in "Superconducting Microprocessors? Turns Out They're Ultra-Efficient (2021)"

Thorondor — Wed, 31 Jul 2024 03:08:12 +0000

Landauer's limit assumes that computation uses a thermodynamically irreversible process and erases bits of information. This is not necessarily true for all useful computers [0]. So theoretically speaking, it's not impossible to create an adiabatic microprocessor. Skepticism is definitely warranted though.

[0] https://en.m.wikipedia.org/wiki/Reversible_computing

New comment by Thorondor in "Companies Say They're Using Microphone Audio to Target Ads [audio] (2023)"

Thorondor — Mon, 13 May 2024 22:29:16 +0000

To prove that it's possible to buy ads targeted on microphone audio. If this kind of targeting was really as widely available as the article implies, a journalist would be able to do it fairly easily and write an article about it.

NASA Public Lessons Learned System

Thorondor — Fri, 08 Mar 2024 14:31:37 +0000

Article URL: https://llis.nasa.gov/

Comments URL: https://news.ycombinator.com/item?id=39641356

Points: 1

# Comments: 0

New comment by Thorondor in "PID Without a PhD (2016) [pdf]"

Thorondor — Mon, 26 Feb 2024 14:34:53 +0000

In my experience, there are a lot of applications that are "trivial" enough that PID works fine. I'm reasonably comfortable with state space modeling for systems with more variables. But OK, I'll bite - always open to picking up something new. What resources would you suggest for someone who wants to learn more about nonlinear controls?

Chess prodigy joked "I'm Taliban" in message, sparked fighter jet escort

Thorondor — Wed, 24 Jan 2024 20:10:55 +0000

Article URL: https://www.dailymail.co.uk/news/article-12991759/amp/Brit-chess-prodigy-tells-Spanish-court-messing-joked-Im-Taliban-told-pals-way-blow-plane-message-sparked-fighter-jet-escort-easyJet-flight-Menorca.htmle-message-sparked-fighter-jet-escort-easyJet-flight-Menorca.html

Comments URL: https://news.ycombinator.com/item?id=39122024

Points: 3

# Comments: 6

National Hurricane Center forecast verification

Thorondor — Fri, 01 Sep 2023 13:03:53 +0000

Article URL: https://www.nhc.noaa.gov/verification/

Comments URL: https://news.ycombinator.com/item?id=37350291

Points: 2

# Comments: 0

Light My Fire (How we start rocket engines, part 2)

Thorondor — Tue, 18 Jul 2023 23:37:40 +0000

Article URL: https://blogs.nasa.gov/J2X/2014/01/24/inside-the-leo-doghouse-light-my-fire/

Comments URL: https://news.ycombinator.com/item?id=36780421

Points: 2

# Comments: 0

New comment by Thorondor in "Nuclear: Not a Faustian bargain, a near-perfect providential gift (2008) [pdf]"

Thorondor — Mon, 15 May 2023 01:32:03 +0000

Nuclear energy is hardly the only power source that has made an entire city uninhabitable. The Banqiao dam failure flooded 30 cities and affected over 10 million people. https://en.m.wikipedia.org/wiki/1975_Banqiao_Dam_failure

Then there's Centralia, PA, which was turned into a virtual ghost town by a coal mine fire. https://en.m.wikipedia.org/wiki/Centralia_mine_fire

And we're not even considering the effects of global warming here. Sure, nuclear has risks, but our civilization needs energy and nuclear has proven to be one of the least risky ways to produce it.