Nostr notes by Hanno Rein

How can one possibly distinguish one from the other?

2026-03-30T20:00:17Z

In reply to nevent1q…2ly9
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How can one possibly distinguish one from the other?

I just gave an interview with a journalist raising concerns about ...

2026-03-30T19:35:02Z

I just gave an interview with a journalist raising concerns about Kessler Syndrom and complaining about megaconstellations in general. And less than 5 minutes later, I see a post about a starlink satellite being involved in a "fragment creation event".

Prof. Sam Lawler (npub1dgc…cla4)

Could someone please vibe-code a tool that monitors my keystrokes ...

2026-03-27T23:47:00Z

Could someone please vibe-code a tool that monitors my keystrokes in vi and then suggest faster alternatives for the most common patterns?

Over the years I've accumulated an inconsistent mess of ...

2026-03-20T23:38:57Z

Over the years I've accumulated an inconsistent mess of integer types in REBOUND. I'm finally cleaning this up by using size_t for all array sizes and indices.

(We're close 😉) ...

2026-03-17T14:22:27Z

In reply to nevent1q…t3vm
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(We're close 😉)

Congratulations!

2026-03-17T14:21:15Z

In reply to nevent1q…fpp6
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Congratulations!

I'm one of two invited keynote speakers at SONAD 2026, the ...

2026-03-15T13:18:10Z

I'm one of two invited keynote speakers at SONAD 2026, the 41st Southern Ontario Numerical Analysis Day. It's a free one day event which this year takes place at the Department of Computer Science in Toronto on May 1st. If you're nearby and interested in numerical analysis and scientific computing, please sign up and join us!

https://www.cs.toronto.edu/~ccc/NAday26/

#hpc #toronto #computerscience

I guess the compiler assumed that because some random element ...

2026-01-13T22:57:47Z

In reply to nevent1q…lufm
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I guess the compiler assumed that because some random element somewhere in r is aligned, some other element in r should also be aligned. It then probably tried to optimizing the different "=NULL" assignments into one using a vector operation. But that failed because the first element in r never actually was properly aligned despite the attribute, and hence neither the other elements.

And of course, as soon as I post it, I find the problem. Despite ...

2026-01-13T22:38:24Z

In reply to nevent1q…rw45
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And of course, as soon as I post it, I find the problem. Despite me searching for an hour already...

The problem was an EXTRA aligned(64) attribute somewhere in the struct r.

I still don't understand the full reason for why this resulted in a segfault at the point it did. But fixing it is good enough for me right now...

FWIW, the code uses #AVX512 at other places in the code. That ...

2026-01-13T22:23:54Z

In reply to nevent1q…4ee0
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FWIW, the code uses #AVX512 at other places in the code. That could be related (i.e. some alignment issue?). But I'm lost as how to find the right spot as the code the debuggers point to has no AVX512.

Very frustrating bug: Without optimization, everything runs fine. ...

2026-01-13T22:21:53Z

Very frustrating bug:
Without optimization, everything runs fine. On O2 or higher, I get a segfault due to an invalid address 0x0. Same for both #clang and #gcc. And I cannot for the life of it figure out where this segfault originates. Both clang and gcc point to a line which doesn't make sense to me. For example in this code
r->a = NULL;
r->b = NULL;
r->c = NULL;
the last line triggers. According to the debugger r is not NULL.

Any suggestions welcome.

A lot of my astronomy colleagues seem to be excited about a ...

2026-01-09T02:05:32Z

A lot of my astronomy colleagues seem to be excited about a billionaire tech bro buying them a new space telescope to play with. I mean sure, better than spending the money on a deep-fake generating AI bot. But has anyone considered just taxing these people and then letting a democratically elected government decide what to do with all that abundant money?

It depends on the bear! ⬆️ is good advise for black bears.

2026-01-02T14:26:52Z

In reply to nevent1q…kvr7
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It depends on the bear! ⬆️ is good advise for black bears.

🎉💫 We had another paper accepted last week. ...

2025-11-10T14:28:48Z

🎉💫 We had another paper accepted last week. Garett Brown, PhD (he/they) (npub13t3…wxv7) was the lead on this one. We study the effect of a substellar flyby on the Solar System and find that there is a surprisingly high probability that such a flyby could have played an important role in shaping the system's architecture.
https://arxiv.org/abs/2412.04583

Today’s harvest: beets, kale, and almost 4kg of carrots. ...

2025-10-28T18:41:40Z

Today’s harvest: beets, kale, and almost 4kg of carrots.

My university now offers burner/loaner phones for people ...

2025-09-10T15:02:01Z

My university now offers burner/loaner phones for people travelling to the US. Funny times.

I'm working on an algorithm which can automatically determine ...

2025-08-28T20:46:50Z

I'm working on an algorithm which can automatically determine the orbital hierarchy for an arbitrary set of point masses and then visualize it in a meaningful way. It's hard! Here's a working example of an octuple system made out of four equal mass circular binaries.

There's an article in the Guardian today about so many ...

2025-07-13T19:08:50Z

There's an article in the Guardian today about so many academic papers being published, it's hard to keep up. I completely agree!

“But nobody really knows what to do about it.”

How about a new journal where each author is only allowed to submit exactly one paper per year. I suspect it would lead to high quality papers because one has to be so selective.

Any thoughts? Peter Coles 🏳️‍🌈 🏳️‍⚧️ (npub1vfp…hct4) ?

https://www.theguardian.com/science/2025/jul/13/quality-of-scientific-papers-questioned-as-academics-overwhelmed-by-the-millions-published

💫🌎 My group's new paper is now on the arXiv. We do ...

2025-07-09T15:40:11Z

In reply to nevent1q…rhmf
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💫🌎 My group's new paper is now on the arXiv. We do something really simple that I'm surprised nobody has done before: a convergence study of N-body simulations of the Solar System. We find that timesteps can be ridiculously large and still yield physical results. Specifically, the timestep can be as large as 1/3 of Mercury's orbital period, or ~32days. This works because the Solar System is chaotic and secular, not mean-motion resonances are driving the evolution. https://arxiv.org/abs/2507.04987

Nostr event nevent1qqsv0mjumsflqut8rnn2zdzvtxzxms8zp5e395p8g7hczdjm5d59zsgzyrt2t4sjqky5ytuljvcgktgdefhek99ysdjvnxskgrnsm4aq363u7gfn6s0

2025-07-04T14:16:57Z

🎉 Paper submitted!

Ice storm #onstorm ...

2025-03-30T15:41:00Z

Ice storm #onstorm

spf=pass, dkim=pass, dmarc=pass!

2025-03-25T21:55:05Z

In reply to nevent1q…knzn
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spf=pass, dkim=pass, dmarc=pass!

Nostr event nevent1qqsxd0q7vzx5axfz2hll7dz06scp4fwzyj5mxdkzvzv7wzr8vfxza4szyrt2t4sjqky5ytuljvcgktgdefhek99ysdjvnxskgrnsm4aq363u7n6lxrq

2025-03-25T21:37:15Z

TIL SPF, DKIM, and DMARC!

all you need is a Linux machine with a sound card and a ...

2025-03-17T00:58:24Z

In reply to nevent1q…msn9
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all you need is a Linux machine with a sound card and a microphone https://github.com/tphakala/birdnet-go

Today’s bird detections in our backyard ...

2025-03-17T00:33:06Z

Today’s bird detections in our backyard

Side note: The servers use 240V. I didn't want to wait for ...

2025-01-31T22:28:48Z

In reply to nevent1q…vrwh
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Side note: The servers use 240V. I didn't want to wait for the university to put a 240V circuit in at work and I don't have an easily accessible 240V socket at home either. So I built this MacGyver-style contraption which combines two 120V outlets on different circuits into one 240V. And yes, this is definitely not up to code for many different reasons and you should absolutely not try this at home yourself.

The System Management Module (SMM) has its own ethernet port. I ...

2025-01-31T22:16:00Z

In reply to nevent1q…m00j
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The System Management Module (SMM) has its own ethernet port. I *think* I've successfully reset the SMM to factory defaults. However, the SMM's network port is completely silent - no traffic at all. Which I *think* is the default. There are instructions in the manual on how to enable the SMM network, but those require me to reach the XCC. So I'm a bit stuck. 🤷‍♂️

Any hints would be appreciated! 😉

So far I'm not having much luck in getting the nodes up and ...

2025-01-31T22:08:15Z

In reply to nevent1q…rzse
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So far I'm not having much luck in getting the nodes up and running. In short, I'm not sure how to access the Lenovo XClarity Controller (XCC). By default it is supposed to try DHCP first and then fallback to a static IP if that fails. I do see some traffic on the ethernet port, including a DHCP request, but strangely the DHCP offers are not accepted. The default static IP also doesn't work. So maybe the default behaviour was changed? It's not clear to me how to reset the XCC to factory defaults

Many thanks to my (former) students ...

2025-01-29T02:51:33Z

Many thanks to my (former) students [@zyrxvo](https://mas.to/@zyrxvo ), Dang, Pejvak and Nick, who helped disassemble 16 nodes of the NIAGARA supercomputer today. Everything is now at UTSC and once we've put it back together, my group will have its own small compute cluster with 640 cores.

This is pretty cool: Amateur astronomers* were able to receive ...

2024-12-22T16:04:35Z

This is pretty cool: Amateur astronomers* were able to receive the carrier signal of Voyager 1. https://www.camras.nl/en/blog/2024/dwingeloo-telescope-receives-signals-from-voyager-1/

* Amateur astronomers who have access to a 25m antenna.

PSA: If you're a scientist and use an LLM for your research, ...

2024-12-02T22:41:48Z

PSA: If you're a scientist and use an LLM for your research, then I don't think very highly of you.

I've finished the bedside tables! #woodworking ...

2024-11-30T22:00:14Z

In reply to nevent1q…lznx
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I've finished the bedside tables! #woodworking

I made good progress on the bedside tables this weekend. ...

2024-11-24T20:27:59Z

In reply to nevent1q…hdka
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I made good progress on the bedside tables this weekend. #woodworking

Upcoming #woodworking project: two bedside tables. Still trying ...

2024-11-16T22:30:31Z

Upcoming #woodworking project: two bedside tables. Still trying to fine tune the design...

☄️+⭐️=💥 My student Dang Pham together with Matthew ...

2024-11-15T12:51:41Z

☄️+⭐️=💥 My student Dang Pham together with Matthew Hopkins in Oxford led a project about fast radio bursts (FRBs) and interstellar objects (ISOs). In short: ISOs colliding with neutron stars could actually explain the observed FRB rate, the observed energy distribution, and even even some of the sub-structure. The paper has been accepted and is now on the arXiv. Check it out!

https://arxiv.org/abs/2411.09135
#astrodon #astronomy #astrophysics

I'm teaching a graduate course on visualizations and #GPU ...

2024-11-11T17:48:36Z

I'm teaching a graduate course on visualizations and #GPU programming this term. This week we'll write an N-body integrator using #WebGPU! #astrodon

Small #woodworking project: laminated and framed a map of ...

2024-11-02T14:57:00Z

Small #woodworking project: laminated and framed a map of #AlgonquinPark to keep track of our trips.