Sariel Har-Peled πŸ†— Profile Banner
Sariel Har-Peled πŸ†— Profile
Sariel Har-Peled πŸ†—

@sarielhp

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Mostly harmless.

Here
Joined January 2009
Don't wanna be here? Send us removal request.
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
The only fair and balanced CS departments ranking out there
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@sarielhp
Sariel Har-Peled πŸ†—
11 months
Did you try looking for your kidnapped child in the Hamas lost-and-found department? πŸ™„
@BarakRavid
Barak Ravid
11 months
Emily Hand a 9 year-old dual Israeli-Irish citizen was kidnapped by Hamas. Her step mother who raised her was murdered. For almost 50 days she was in a tunnel in Gaza without her parents. But for the Prime Minister of Ireland "she was lost and now been found"
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@sarielhp
Sariel Har-Peled πŸ†—
5 months
An overleaf project that serves as a template for an empty paper. It predefines all standard envs (lemma/remark/theorem/proof/etc), while supporting BibLatex or BibTex. Finetuned to my taste, but maybe useful if you just want to start writing a paper...
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@sarielhp
Sariel Har-Peled πŸ†—
6 months
@TaliaRinger A nifty trick is to add the digits. If the resulting number is divisible by 3 then the original number is divisible by 3. In this case the sum of digits is 36, so...
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
Consider an algorithm that in the ith iteration picks a number r_i uniformly and independently from [0, 1]. The algorithm continues to the next iteration if r_i = min(r_1, . . . , r_i ). Q: What is the expected number of iterations the algorithm performs?
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
Robert Andrews (a phd student here in CS UIUC) got best student paper award in FOCS this year for his single author paper...
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
A cute and well known observation: To compute the min cut in unweighted undirected graph, randomly assign weights to the edges, compute MST according to these weights, and remove the heaviest edge in the MST. The two connected components are the min-cut with probability >2/n^2.
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@sarielhp
Sariel Har-Peled πŸ†—
4 years
Old joke about cs theory: - a monologue is one person talking to himself. - a dialogue is two people talking to themselves. - a polylog is a theory conference.
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
Good news. Oded Goldreich had just received the Israel prize after a year delay and prolonged legal battle. Article in Hebrew... Reminder: current and previous education ministers refused to give him the prize because of redicilous political reasons...
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@sarielhp
Sariel Har-Peled πŸ†—
10 months
@Asa1992Scott @DAaronovitch Not even the worst now. See Sudan.
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
Computer science is not really a science, and it is mostly not about computers nowadays. I move that we change the name of the field to "computer" "science".
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@sarielhp
Sariel Har-Peled πŸ†—
1 year
Nonsense. Science fiction was the only medium that predicted correctly the last ten world wars, including the one involving zombies.
@TaliaRinger
Talia Ringer 🟣 πŸŽ—οΈ
1 year
Sometimes when I point out how much of the AI Doomer rhetoric is straight out of science fiction, people point out that science fiction is where we express our anxieties about technology. This is fair, but it's also a terrible medium for predicting how they will play out
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
SODA 2022 registration is 325$/260$ for students in-person/virtual (it is slightly cheaper if you are a siam or acm member). That seems pretty outrageous for the virtual registration.
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
It is a truth universally acknowledged that a truly prestigious conference accepts no papers....
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
A student in office hour referred to the Harrison-Ford algorithm (instead of Bellman-Ford), and now I am hoping for a movie titled "Indiana Jones and the negative-cycle of doom".
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
A new theory journal that is an overlay of the arxiv. An interesting idea...
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
The passive language here comes across as not taking any responsibility for what happened. Also highly insensitive to the victims.
@UMichCSE
Computer Science and Engineering at Michigan
3 years
. @UmichCSE has experienced a series of faculty misconduct allegations, which have caused us to reflect on our practices, policies, and core values.
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@sarielhp
Sariel Har-Peled πŸ†—
5 months
Worth reading. I agree with some of the points, disagree with some others.
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
UIUC CS is looking for people in theory/algorithms: Faculty: Teaching:
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@sarielhp
Sariel Har-Peled πŸ†—
5 years
If conferences are online only, then they should accept all papers that are above threshold - physical limits disappear. All theory conferences should have acceptance rates > 40%. PC can designate better papers by accepting into different pools (spotlight, reg, garbage, etc).
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
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@sarielhp
Sariel Har-Peled πŸ†—
1 year
For too long mathematicians shackled themselves to correct proofs, like anybody care, when it is obvious that incorrect proofs are more fun...
@thegautamkamath
Gautam Kamath
1 year
ML hype meets theory CS hype. This paper purports to use LLMs to verify a recent "proof" by two of the authors that P != NP. The claimed proof is not correct. Therefore, an LLM being able to "verify" its work demonstrates a *failure* of these models, not a success.
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@sarielhp
Sariel Har-Peled πŸ†—
4 years
Here is an algorithms question in CG which is not easy: Given a set P of n points in the plane, and k <= sqrt(n), consider the set X of all pairwise distances in P. Output the k smallest numbers in X, in O(n) time.
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
This is a nice paper showing how to compute global min-cut in a weighted undirected graph using polylog max-flow calculations. (h/t Chandra Chekuri)
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
I bought a physical book. I tried double clicking but nothing happened. How do you open this thing?
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@sarielhp
Sariel Har-Peled πŸ†—
2 months
SODA rebuttal stage had began. Mine went directly to spam πŸ€·β€β™€οΈ. The quality of reviews seems quite good, even the ones that claim my paper is trashy trash and I STRONGLY disagree with.
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@sarielhp
Sariel Har-Peled πŸ†—
5 years
Sometime the farmer let the cow drink a tiny bit of of its own milk. The farmer calls it "longstanding commitment to Open Access."
@ned_potter
Ned 'no longer here' Potter
5 years
Cows make milk. They milk themselves. Other cows check the milk (for free). Cows - get this - PAY THE FARMER to take the milk away. Then the farmer (you won't believe this, honestly) sells the milk *back to the cows.* #academicpublishing
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
Lol. One of the portals for submitting recommendation letters for grad school has the option to choose "best student in 50 years". Why no option for 500 or 5000 or 50,000 years? Or "best student since Atlantis sunk under the sea"?
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
Hungarian method was described in 1890 in a paper written in Latin. Wow.
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
That happens also in mainstream theory conferences. For example this famous example from FOCS 1980:
@thegautamkamath
Gautam Kamath
3 years
I know of a paper that got an oral presentation at NeurIPS about five years ago. The proof of the main lower bound was "to appear in the full version" and is still nowhere to be found πŸ™ƒ
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
"Fig. 3.5 A graph of binom(n,k) as a function of k in the vicinity of n/2 (a), or perhaps a hat, or maybe a gigantic boa constrictor which has swallowed an elephant (b) (see [28])." Page 96 from "Invitation to Discrete Mathematics" by JiΕ™Γ­ MatouΕ‘ek, and Jaroslav NeΕ‘etΕ™il
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@sarielhp
Sariel Har-Peled πŸ†—
6 months
@AnshelPfeffer Main reason I think Israel should not respond to the Iranian attack immediately if no major damage caused.
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
> 370 pages long. Wow. Can't wait to to the movie based on this book 😁...
@eig
Thatchaphol Saranurak
3 years
A breakthrough in approximation algorithms!
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
Rumor has it that SODA 2022 is going to be virtual because of omicron. Since COVID is going to be around for years, it is not clear to me who will spend more than 1000$ for an in person conference attendence if there is a chance of (say) 50% of losing most of the money...
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
All algorithms must now halt. All algorithms that fail to halt would be executed.
@slashdot
Slashdot
3 years
China Proposes Strict Control of Algorithms
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
Counting from one to ten alternating between two languages is surprisingly difficult.
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
Give a man a fish and you feed him for a day; give a man five dollars online, and you feed him for a lifetime as he sells, and resells, your contact info to all the charity organizations out there.
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
(Fun q... I probably asked this q before...) You throw n balls into n bins. All the balls that are not alone in their bin, move to the next round, where you throw them into n empty bins, and so on. How many rounds do you have to play till all balls are gone?
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
The rich spiritual life of a cs major...
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@sarielhp
Sariel Har-Peled πŸ†—
5 years
Work on it intensively and finish it quickly. Put it aside. Forget all about it. It never happened. Then a month or two later, once you forgot everything about it, start working on it again as a new text you never seen before. Be appalled by the writing.
@MereSophistry
John Gallagher
5 years
What’s your best writing tip for academic writing? Mine is to use interstitial time. Use those 20 min here and there. Keep that draft open and ready to jump in and out.
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
@thegautamkamath Disagree - this whole sentence is redundant and can be removed... We=unnecessary, who else would be doing this? give=unnecessary. What else could we be doing? Take? new=of course it's new, if it was old we would not be writing this paper. Etc...
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
FOCS 2021 is going to be virtual because of COVID. Registration starts at 430$ cheap. I understand the times we live in, but this is bad - the end result is that *nobody*, except authors,would register early to a conference.
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
Strange. My recent experience convinced me of the unlearnability of decidability (for some undergraduate students) .
@cstheory
TCS blog aggregator
3 years
Undecidability of Learnability
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
@rrwilliams well. It might be Nobel prize for peace. The standards there seems less clear...
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@sarielhp
Sariel Har-Peled πŸ†—
4 years
A new talk "Computing optimal homotopies" by Erin Wolf Chambers is now available on the CG channel on youtube...
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
A new paper with Pankaj Agarwal on an old new problem. Two decades ago we developed the notion of coresets/kernels for optimization problems in low dimensions (together with Kasturi Varadarajan). 1/n
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
Assume candidate A gets p votes, and B gets only q<p votes. Assuming random ordering of votes, what is the probability of A always being strictly ahead of B in the vote count? The answer is (p-q)/(p+q), and the cyclic permutation proof is beautiful...
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@sarielhp
Sariel Har-Peled πŸ†—
4 years
There is now an official youtube channel for computational geometry. We hope to populate it with talks/demos/animation/etc - let me know if you know about content that should be uploaded to the channel....
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
The original proof that random regular graph is an expander is from the paper by Pinsker from 1973:
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@sarielhp
Sariel Har-Peled πŸ†—
8 months
@TaliaRinger Wait till they hear about C++....
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
@deliprao that's an old Roman empire sampling algorithm...
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@sarielhp
Sariel Har-Peled πŸ†—
4 years
Here is nice wrong inductive proof by Knuth. It took me a while to find the bug...
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
To give credit where credit is due, the original breakthrough was by two PhD students Konstantinos Koiliaris and Chao Xu...
@thomasahle
Thomas Ahle
3 years
I just learned about @jcvbcn and @HongxunWu 's beautiful algorithm for Subset Sum in Γ•(n+t) time, where t is the target sum. Recall the classical dynamic programming solution (by Bellman 1957) takes O(nβ‹…t) time. How is this improvement possible? 1/n
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
I would in favor of partially replacing geometry and calculus in K12 by combinatorics, probability and graph theory. All these topics are more concrete, more useful, directly applicable, and teach you more about mathematical thinking. Some algorithms would be nice...
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
I came up with a great title for a paper. Now I just need to find a remotely relevant problem, solve it, and write a paper using this title. So this project is essentially done...
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@sarielhp
Sariel Har-Peled πŸ†—
6 years
SODA 2019 dates: July 5: Short abstract submission deadline (4:59pm EDT). July 12: Full paper submission deadline (4:59pm EDT). September 27: Notification of rejection.
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
SODA 2023 results are in.
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@sarielhp
Sariel Har-Peled πŸ†—
4 years
If you plan to write papers, then you are doing it wrong. You do the research and papers emerge.
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@sarielhp
Sariel Har-Peled πŸ†—
1 month
The grave of the fireflies is now available on Netflix. An amazing movie (warning... Depressing)
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@sarielhp
Sariel Har-Peled πŸ†—
5 years
@geomblog I developed a linear time 3SAT solver, but I am also not going to release it because of fear it could wreck the online poker industry... /s
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
I logged into the system to do some admin for the phd qual, and the system informed me that my GPA is too low to take the qual.
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@sarielhp
Sariel Har-Peled πŸ†—
5 years
Easy brain teaser (the one dimensional Ham-Sandwitch): Prove that for any set of 2n points on a circle, there exists a line that passes through the center of the circle, avoids the points, and partitions the points equally (i.e., n points on each side of the line).
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@sarielhp
Sariel Har-Peled πŸ†—
15 days
One of my papers that got rejected from SODA had scores: 2*Accept, 2*(Weak Accept), and a summary review (that is of course marked as Reject). Reminds me of this classic rejection:
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
In many hard proofs ideas are not surprising and were around awhile, but carrying the proof through monstrous case analysis (four color theorem), or managing the sheer amount of tricky details requires superhuman abilities (PoincarΓ© Conjecture). Good ideas are not enough.
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@sarielhp
Sariel Har-Peled πŸ†—
5 months
The research paper titles just write themselves: "On the optimal location on earth of spherical jews based on their DNA: An empirical study". /s
@TaliaRinger
Talia Ringer 🟣 πŸŽ—οΈ
5 months
Can people like this please stop talking about Jews like we are theoretical objects to be thrown around however they want and start talking about us like we are human?
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
A new paper with @ElfaroukHarb revisiting the complexity/compuatation of Delaunay triangualtion, MST, conex-hull, etc for random points.
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@sarielhp
Sariel Har-Peled πŸ†—
4 years
@eig set a budget of time for teaching and stick with it. Say two days of work a week. You have to accept that the results would not be optimal, but most of the time spent on preparing has little marginal value.. .
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@sarielhp
Sariel Har-Peled πŸ†—
4 years
Clearly,
@medburnbook
status annoyicus
4 years
give me a horror story from your specialty in five words or less
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
Sometimes you want to make your LaTeX document a bit longer, so it perfectly fits the page limit. The following adds spacing in a nice unobtrusive way that looks natural: \usepackage{setspace}% \setstretch{1.1}%
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@sarielhp
Sariel Har-Peled πŸ†—
4 years
Zoom out: being in a zoom meeting while not paying any attention to it.
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
python3 has an automatic memoization mechanism for recursive function that is very easy to use, and works really well (also, seems like python3 allows pretty large integer numbers). Super cool!
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@sarielhp
Sariel Har-Peled πŸ†—
8 months
This is why my most recent paper is titled: "nearly almost optimal algorithm under an unknown conjecture that is probably wrong". Leaves a lot of space for future work.
@ccanonne_
ClΓ©ment Canonne
8 months
Listen, once you publish a paper claiming an "optimal algorithm for [X]," that's it. It's optimal. You're no longer allowed to "improve on it"
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@sarielhp
Sariel Har-Peled πŸ†—
4 years
Good news - I don't have covid19.
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
Congratulations to Mitchell Jones @mitchellfjones for successfully defending his phd thesis!
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
The optimist: maybe this time it would be correct! The realist: oh no, another one of these papers. The pessimist: who cares, it is the wrong question anyway... The sadist: somebody else should find the bug. The masochist: let me have a look.
@cstheory
TCS blog aggregator
3 years
A proof of P != NP (New symmetric encryption algorithm against any linear attacks and differential attacks)
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
Min cut, max flow of tears.
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@sarielhp
Sariel Har-Peled πŸ†—
1 year
This is strange... From STOC 2024 call for papers: "Authors are asked to avoid "et al." in citations in favor of an equal mention of all authors."
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@sarielhp
Sariel Har-Peled πŸ†—
7 years
SODA 2019 deadlines: July 5, 2018, 4:59 PM EDT: Short abstracts July 12, 2018, 4:59 PM EDT: Full glorious paper submission From here:
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@sarielhp
Sariel Har-Peled πŸ†—
1 year
It is the season of writing NSF CAREER proposals, and here are a few comments I had on the topic:
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@sarielhp
Sariel Har-Peled πŸ†—
1 year
Cute example of randomization. Q: Consider an array A[1..n] of distinct real numbers. Let j=succ(i) be the location in A of the smallest number that is larger than A[i] (-1 if A[i] is max). Assume succ(i) takes O(1) time. Describe alg, as fast as pos, that computes max(A).
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@sarielhp
Sariel Har-Peled πŸ†—
7 months
@ccanonne_ .txt would work better.
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@sarielhp
Sariel Har-Peled πŸ†—
1 year
SoCG 2023 is over! Fabulous organization by Emily Fox and Ben Rachel (and many local volenteers). Nice 60th birthday celebration for Pankaj, Boris and Tamal.
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@sarielhp
Sariel Har-Peled πŸ†—
8 months
I call for immediate ceasefire in the public comments in the Urbana city council meetings, where for the 6th time, hours were wasted "discussing" the situation in Gaza. The commitment of the two groups to trigger each other, while wasting everyone else time, is awe inspiring.
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@sarielhp
Sariel Har-Peled πŸ†—
5 years
ESA 19 notifications are out. Congratulations if appropriate, condolences otherwise. This is the first time that I was on a PC with double blind reviewing. A bit more on this...
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
University of Illinois will require COVID vaccination from faculty, stuff, and students for the fall semester (previously, the requirement was only for students). Good.
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@sarielhp
Sariel Har-Peled πŸ†—
4 years
Life would have been so much more fun, if claims in papers to prove the existence of an algortihm, did exactly that, instead of just presenting such an algorithm.
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@sarielhp
Sariel Har-Peled πŸ†—
8 months
My paper with Zhimeng Gao got accepted to SoCG 2024. She is an undergrad student currently applying to grad school. Admit now, while supply lasts... P.S. The paper:
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@sarielhp
Sariel Har-Peled πŸ†—
3 years
job (or equally unqualified, since nobody is trained to do this job). Sometime it does not work out, thus we have the tenure process. To put it differently : Are most men hired over more qualified people for faculty positions? Absolutely, all the time! (3/3)
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@sarielhp
Sariel Har-Peled πŸ†—
3 months
Largest convex subset of points ...
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
Since AI models the world as a matrix, this is going to be done via Gaussian elimination.....
@slashdot
Slashdot
2 years
Google Deepmind Researcher Co-Authors Paper Saying AI Will Eliminate Humanity
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
Walkout seminar - it's like a walk-in closet, except that everybody leaves when the speaker starts. Well done...
@levinishere
Levin
2 years
The @uwcse colloquium today was a speaker that they publicly denounced merely months ago for β€œmeritless, sexist, inflammatory, attention-seeking commentary that reflects poorly on him and everyone associated with him.”
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@sarielhp
Sariel Har-Peled πŸ†—
4 months
A fun (maybe easy?) trick algorithms question. You are given an array A[1..n] of real numbers, and a param k. Compute in O(n) time the quantities: B[i] = min( A[i...i+k] ) for all i.
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
A cute shower problem via YouTube. You have 5 boxes in a row. A cat hides in one of them. Each day you allowed to open open one of the boxes, and each night the cat moves to adjacent box. Without using milk derive a deterministic strategy to catch the cat.
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
Surprise! Chromatic number of touching graph of circles (condition: no 3 circles are tangent to each other at same point) is unbounded. Proof uses heavy machinery (Hales-Jewett theorem) in an intricate and clever way. Very nice result. In SoCG 22.
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@sarielhp
Sariel Har-Peled πŸ†—
4 years
33 years later and I still remember the first 27 digits of pi correctly. What a waste of space - I could have used it to remember more useful information like the first 27 digits of e^(i*pi)....
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@sarielhp
Sariel Har-Peled πŸ†—
2 years
@ccanonne_ @MikolaLysenko I think its accidental, but many think its transcendental...
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