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Ben Grimmer

@profgrimmer.bsky.social
531 followers 249 following 100 posts

Visiting Assistant Prof @MITSloan Assistant Prof @JohnsHopkinsAMS, PhD in Optimization @CornellORIE Mostly here to share pretty maths/3D prints, sometimes sharing my research

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Ben Grimmer @profgrimmer.bsky.social · 03/08/2026
The latest "News and Views" issue from SIAM's Group on Optimization just came out. The issue highlights Alex Wang, Kevin Shu, and my work on "subgame perfect" algorithm design. These algorithms use game theory ideas to describe the best way for algorithms to adapt at runtime 1/4
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Ben Grimmer @profgrimmer.bsky.social · 23/05/2026
I'm excited to share some joint work done with TaeHo Yoon. We considered algorithm design for fixed-point problems. This area models gradient descent, minimax optimization, and more. Below, I give the wild ride of this paper. Mathematically, it is gorgeous.
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Ben Grimmer @profgrimmer.bsky.social · 01/05/2026
Last year, Mateo Diaz and Ian McPherson began searching for provably good nonsmooth optimization methods on manifolds. Oh boy, did I quickly learn the hard subtleties of numerical work on manifolds, especially combined with finicky subgradients.
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ArXiv math.OC Optimization and Control @optb0t.bsky.social · 01/05/2026
📚 New Arxiv Paper Title: Nonsmooth Riemannian optimization with inexact manifold primitives via bundle methods Authors: Mateo D\'iaz, Benjamin Grimmer, Ian McPherson Read more: arxiv.org/abs/2604.27078
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Sebastian Pokutta @spokutta.bsky.social · 13/04/2026
For a decade it was open whether Frank-Wolfe's O(1/√ε) rate on strongly convex sets is tight. We show it is: Ω(1/√ε), even for a simple quadratic on a unit ball.
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Ben Grimmer @profgrimmer.bsky.social · 11/03/2026
For the second morning this week, one of my phd students defended (successfully!) 🎉🎓🎉 Today, Alan Luner defended his excellent work, "On Large-Scale Optimization: Optimal Methods and Computer-Assisted Algorithm Design". I promise this is the last such announcement for the year
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Ben Grimmer @profgrimmer.bsky.social · 09/03/2026
This morning my PhD student Thabo Samakhoana defended his thesis (successfully!) 🎉🎓🎉 Was a great five years working with him towards his thesis "On Optimal Smoothings and their Applications to Optimization and Deep Learning"
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Ben Grimmer @profgrimmer.bsky.social · 27/02/2026
This paper generated me new office decorations as well. Below is the strongly convex set we designed that is provably hard for all Frank-Wolfe methods (at least for two steps). The paper builds this "evil" shape in d dimensions able to counteract any d/2 step method
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Ben Grimmer @profgrimmer.bsky.social · 27/02/2026
A small digression on something I find strange in accelerated convex optimization theory: Since the 80s, in unconstrained minimization by gradient methods, smoothness is known to allow a fast O(1/T^2) convergence rate by Nesterov. Nemirovski and Yudin give matching lower bounds.
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Ben Grimmer @profgrimmer.bsky.social · 12/02/2026
Lately, non-crossing partitions have shown up out of nowhere in my research, which have a lovely duality structure. This inspired some good art and fractals :) Wanted to share the fun here (just sharing the pretty art for now, the research story will come in due time) 1/4
5 circles with yarn between them representing non-crossing partitions and their duals
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Ben Grimmer @profgrimmer.bsky.social · 02/02/2026
Happy to announce that my work "On optimal universal first-order methods for minimizing heterogeneous sums" just received the Optimization Letters Best Paper Prize. link.springer.com/journal/1159... This work is part of a larger trend, fighting the brittleness of classic smooth/nonsmooth models.
link.springer.com
Optimization Letters
Optimization Letters covers all aspects of optimization, including theory, algorithms, computational studies, and applications. This journal provides an ...
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Ben Grimmer @profgrimmer.bsky.social · 11/01/2026
Sunday morning spent setting up my office in the new @hopkinsdsai.bsky.social building. I gained a good amount more wall space, so I have the freedom to grow my collections again
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Johns Hopkins Data Science and AI Institute @hopkinsdsai.bsky.social · 19/12/2025
Join us in advancing data science and AI research! The Johns Hopkins Data Science and AI Institute Postdoctoral Fellowship Program is now accepting applications for the 2026–2027 academic year. Apply now! Deadline: Jan 23, 2026. Details and apply: apply.interfolio.com/179059
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Ben Grimmer @profgrimmer.bsky.social · 13/12/2025
My student Thabo Samakhoana and I have been obsessed with smoothings lately. The softmax/logSumExp smoothing seems to be the standard everywhere in ML and optimization. So, in what sense is this choice "optimal"? We found some "elementary" answers, both good and bad news (1/4)
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Ben Grimmer @profgrimmer.bsky.social · 20/11/2025
A new paper out with TaeHo Yoon and Ernest Ryu: We looked at the design of optimal fixed-point algorithms. That is, seeking to approximately solve T(y)=y using as few evaluations of the operator T() as possible. Maximally efficient methods are "minimax optimal" 1/
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Ben Grimmer @profgrimmer.bsky.social · 18/11/2025
Lately, I have been obsessed with developing theoretically based optimization algorithms that actually attain the best practical performance. Alas, the classic model of minimax optimal methods is overly conservative; it overfits to tune its worst-case. We found a path forward 1/
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Ben Grimmer @profgrimmer.bsky.social · 14/08/2025
Enjoyed being part of the Brin Mathematical Research Center's summer school on Scientific Machine Learning last week. Many very good talks and always nice to visit UMD!
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Ben Grimmer @profgrimmer.bsky.social · 12/08/2025
📢 Excited to share a new paper with PhD student Thabo Samakhoana. Nonsmooth optimization often uses smoothings, nearby smooth functions or sets. Often chosen in an ad hoc fashion. We do away with ad hoc, characterizing optimal smoothings for convex cones and sublinear functions
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Henrik A. Friberg @hafriberg.bsky.social · 05/08/2025
Oh, that’s so satisfying! I stopped at the 4-norm ball thinking I had the solution as it fits the hole like a pot lid (has a perfect circle as an intersection).
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Ben Grimmer @profgrimmer.bsky.social · 05/08/2025
Yesterday I posted a maths puzzle that AIs all failed at (thanks for running the premium versions @xy-han.bsky.social and Ernest Ryu). The puzzle just needs elementary reasoning about p-norm balls (third row on my shelf below). This thread gives the puzzle, solution, and a 3D printed demo :)
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Ben Grimmer @profgrimmer.bsky.social · 05/08/2025
I've invented a simple, lovely math puzzle I expect every AI fails: Suppose you're a mathematical sailor at sea on a boat that has a perfectly cylindrical hole in the floor. All you brought is a collection of every p norm ball except p=2 (drat!). What do you do to cork the hole and save yourself?
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Sam Power @spmontecarlo.bsky.social · 26/05/2025
very cool talk: youtu.be/K_dhTP2I2uo?... "Near-Linear Runtime for a Classical Matrix Preconditioning Algorithm" - Jason Altschuler
youtu.be
Jason Altschuler - Near-Linear Runtime for a Classical Matrix Preconditioning Algorithm
YouTube video by Institute for Pure & Applied Mathematics (IPAM)
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Ben Grimmer @profgrimmer.bsky.social · 30/04/2025
Lots of great questions and engagement from Wisconsin folk! They were quick at turning around and getting it online. See below: www.youtube.com/watch?v=QNfq...
youtube.com
Ben Grimmer - "Optimizing Optimization Methods, To and Beyond Minimax Optimality"
YouTube video by UWMadison SILO Seminar
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Ben Grimmer @profgrimmer.bsky.social · 30/04/2025
Just landed in Madison! Tomorrow, I'll be sharing my work optimizing optimization methods, to and beyond minimax optimality in their SILO seminar. Will share a link to the talk on YouTube after
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Quanta Magazine @quantamagazine.org · 29/03/2025
The optimization technique of gradient descent is like feeling your way down a mountain in the dark. You may not be able to see the way, but you’ll eventually reach the lowest point in the area. (From the archive) www.quantamagazine.org/risky-giant-...
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Ben Grimmer @profgrimmer.bsky.social · 15/03/2025
My PhD students are awesome. They gave my fiancee(wife) and I this gorgeous cherry blossom card for our wedding and soon honeymoon in Japan <3
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Ben Grimmer @profgrimmer.bsky.social · 12/03/2025
As an early wedding present (happening this Saturday!), my dad made me a custom shelf to hold my collection of unit norm balls! Rockafellar+Wets's thick textbook is included for reference.
A 7x7 shelf of unit balls in different norms. 3D printed
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Ben Grimmer @profgrimmer.bsky.social · 11/03/2025
New (first) paper with my student Aaron Zoll :) We consider first-order methods for a ridiculously general model: minimizing a convex composition of functions g_j(x) that vary heterogeneously in whether they are smooth, nonsmooth, convex, strongly convex or anything in between.
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Alfred P. Sloan Foundation @sloanfoundation.bsky.social · 18/02/2025
🎉Congrats to the 126 early-career scientists who have been awarded a Sloan Research Fellowship this year! These exceptional scholars are drawn from 51 institutions across the US and Canada, and represent the next generation of groundbreaking researchers. sloan.org/fellowships/...
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Ben Grimmer @profgrimmer.bsky.social · 15/02/2025
PhD students set up arts and crafts to make Valentine's mailboxes and collect cards. They (slide) rule :)
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Ben Grimmer @profgrimmer.bsky.social · 29/01/2025
Newest office addition might be the biggest computer in my department! (Assuming compute is measured by length)
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Nikhil Garg @nkgarg.bsky.social · 25/01/2025
Postdoctoral position at @cornelluniversity.bsky.social, "from all areas of research that advance the state of the art in data science and the health sciences, extending the reach of data-driven research into novel medical application domains" Happy to chat! academicjobsonline.org/ajo/jobs/29529
academicjobsonline.org
Cornell University, Center for Data Science for Enterprise and Society
Full service online faculty recruitment and application management system for academic institutions worldwide. We offer unique solutions tailored for academic communities.
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Ben Grimmer @profgrimmer.bsky.social · 16/01/2025
NeurIPS has released recordings of talks! I had the privilege to speak in the OPT-ML Workshop: neurips.cc/virtual/2024... My talk presents a solution to the ''minimization game'' for smooth convex problems (ie a subgame perfect method that optimally adapts to any gradients seen)
neurips.cc
Optimization for ML WorkshopNeurIPS 2024
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Ben Grimmer @profgrimmer.bsky.social · 16/01/2025
Proud Advisor Moment: One of my first advisees, Danlin Li, now a PhD at Georgia Tech, just had our paper extending her Masters thesis accepted to Math Programming! She gives a novel primal-dual way to understand the classic (primal) subgradient method Check it out: arxiv.org/abs/2305.17323
arxiv.org
Some Primal-Dual Theory for Subgradient Methods for Strongly Convex Optimization
We consider (stochastic) subgradient methods for strongly convex but potentially nonsmooth non-Lipschitz optimization. We provide new equivalent dual descriptions (in the style of dual averaging) for ...
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Ben Grimmer @profgrimmer.bsky.social · 08/01/2025
Continuing to use January's freedom, some exposition on OWL Norms: Their unit balls are all Catalan solids (every face is the same). So the dual balls are all Archimedean solids (every corner is the same) www.ams.jhu.edu/~grimmer/OWL... Files to make your own: www.printables.com/model/113805...
Two collections of norm balls, OWL norms and their duals shown in two rows on shelves in Benjamin Grimmer's office
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Ben Grimmer @profgrimmer.bsky.social · 06/01/2025
January has given me some great free time :) First link gives some exposition on how this binary slide rule works. Second link gives the design files if you want one. Many libraries have 3D printers to make this for you nowadays www.ams.jhu.edu/~grimmer/Sli... www.printables.com/model/113795...
ams.jhu.edu
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Ben Grimmer @profgrimmer.bsky.social · 29/12/2024
The way computers store real numbers (floating point) is exactly the same as how our grandparents did math mechanically, slide rules and log scales. I'm mass producing binary slide rules to give students on day one of my "Intro to Computational Math" this Spring :)
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Ben Grimmer @profgrimmer.bsky.social · 20/12/2024
Yue Wu (a great PhD student) posted his first paper with me to arxiv, on stochastic nonconvex nonsmooth optimization. We give unified analysis for variance-reduced prox-linear methods, identifying a neat Pareto frontier of state-of-the-art methods. Check it out: arxiv.org/abs/2412.15008
arxiv.org
Some Unified Theory for Variance Reduced Prox-Linear Methods
This work considers the nonconvex, nonsmooth problem of minimizing a composite objective of the form $f(g(x))+h(x)$ where the inner mapping $g$ is a smooth finite summation or expectation amenable to ...
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Ben Grimmer @profgrimmer.bsky.social · 14/12/2024
📢 #NeurIPS2024 Folk, if you like minimax optimal gradient methods, set your alarms for tomorrow morning: 9am in the West Ballroom A I'll be giving a plenary at the OPT-ML workshop on optimizing GD steps and subgame perfect methods, all developed with Alex L Wang and Kevin Shu
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Ben Grimmer @profgrimmer.bsky.social · 11/12/2024
My collaborator Alex L Wang wrote a nice blog post about the "Performance Estimation" view of Nesterov's Accelerated Gradient Method. I think it's a nice read (glad Bluesky doesn't suppress posts for having a link): web.ics.purdue.edu/~wang5984/bl...
web.ics.purdue.edu
Alex L. Wang – What is momentum? – A PEP view
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Ben Grimmer @profgrimmer.bsky.social · 10/12/2024
New work out with Alex L Wang and Kevin Shu going beyond minimax optimal gradient method design! Kim and Fessler designed an optimal method (OGM), with the best worst-case over all smooth convex problems. Alas, on easier problems, it may be slow, its worst case occurs on x^2!
Trajectory of OGM on a quadratic, its very slow
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Ben Grimmer @profgrimmer.bsky.social · 07/12/2024
Leveling up from 3D printing: I present a p=4/3 norm ball ceramic (Moreau, featured in background, likes it)
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Johns Hopkins Data Science and AI Institute @hopkinsdsai.bsky.social · 02/12/2024
Congratulations to all @johnshopkins.bsky.social researchers participating in #NeurIPS2024! Check out all @johnshopkins.bsky.social accepted papers, tutorials, and workshops at ai.jhu.edu/news/johns-h....
ai.jhu.edu
Johns Hopkins researchers to present work at NeurIPS 2024 - Johns Hopkins Data Science and AI Institute
Johns Hopkins researchers, including several affiliated with the Johns Hopkins Data Science and AI Institute, will present their research at tutorials, poster presentations, and workshops during the 2...
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Ben Grimmer @profgrimmer.bsky.social · 30/11/2024
I'd like to add some more spectrahedron's to my office and to serve as examples in some upcoming talks. My current working examples come from approximating the MAX-CUT polyhedron for 3x3 and 4x4 matrices. Anyone have recommendations? Details on MAX-CUT bodies below: www.ams.jhu.edu/~grimmer/Max...
Photos of max-cut sdp approximations for 3x3 matrices, showing an inner approximation, the true polyhedron, and the sdp outer approximationPhotos of max-cut sdp approximations for 4x4 matrices, showing an inner approximation, the true polyhedron, and the sdp outer approximation restricted to a 3D subspacePhotos of max-cut sdp approximations for 4x4 matrices, showing an inner approximation, the true polyhedron, and the sdp outer approximation restricted to a different 3D subspace
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Ben Grimmer @profgrimmer.bsky.social · 27/11/2024
A very neat result!! Opens a new frontier to push Gradient Descent's theory! Wild that we might have different optimal exponents for the obj gap convergence rates 1/T^p of Short Stepsize GD: p=1 Anytime GD: p>=1.03 Final Iterate GD: p=1.27 (conjectured) General Grad Methods: p=2
arxiv.org
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Jason Lee @jasondeanlee.bsky.social · 27/11/2024
arxiv.org/abs/2411.17668 Our postdoc zihan slays another COLT open problem! proceedings.mlr.press/v247/kornows...
arxiv.org
Anytime Acceleration of Gradient Descent
This work investigates stepsize-based acceleration of gradient descent with {\em anytime} convergence guarantees. For smooth (non-strongly) convex optimization, we propose a stepsize schedule that all...
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Dirk Lorenz @dirque.bsky.social · 18/11/2024
I made a #starterpack for computational math 💻🧮 so please 1. share 2. let me know if you want to be on the list! (I have many new followers which I do not know well yet, so I'm sorry if you follow me and are not on here, but want to - drop me a note and I'll add you!) go.bsky.app/DXdZkzV
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Ben Grimmer @profgrimmer.bsky.social · 15/11/2024
The DeepMath2024 Conference to going on today and tomorrow at UPenn! Talks are being streamed live online at www.youtube.com/watch?v=A0Oh... for anyone around the world interested!
youtube.com
DeepMath 2024
YouTube video by DeepMath
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Ben Grimmer @profgrimmer.bsky.social · 12/11/2024
Each Fall I get to teach a Freshman Experience Course where a few freshman and I explore some fun math The last weeks each year, they take the lead and design and 3D print something. This year, they made loaded dice. Next week theyll be rolling and doing statistical validation
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Ben Grimmer @profgrimmer.bsky.social · 11/11/2024
Been thinking about smoothing of nonsmooth functions lately. Printed the 1-norm function and its Moreau Envelope, a classic smoothing tied to the proximal operator (Happy to share the source. If you teach anything related to prox operators, it could be a good aid to pass around)
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