Archive for anime

diffusions, sampling, and transport

Posted in Books, pictures, Statistics, Travel, University life with tags , , , , , , , , , , , , , on November 21, 2022 by xi'an

The third and final day of the workshop was shortened for me as I had to catch an early flight back to Paris (and as I got overly conservative in my estimation for returning to JFK, catching a train with no delay at Penn Station and thus finding myself with two hours free before boarding, hence reviewing remaining Biometrika submission at the airport while waiting). As a result I missed the afternoon talks.

The morning was mostly about using scores for simulation (a topic of which I was mostly unaware), with Yang Song giving the introductory lecture on creating better [cf pix left] generative models via the score function, with a massive production of his on the topic (but too many image simulations of dogs, cats, and celebrities!). Estimating directly the score is feasible via Fisher divergence or score matching à la Hyvärinen (with a return of Stein’s unbiased estimator of the risk!). And relying on estimated scores to simulate / generate by Langevin dynamics or other MCMC methods that do not require density evaluations. Due to poor performances in low density / learning regions a fix is randomization / tempering but the resolution (as exposed) sounded clumsy. (And made me wonder at using some more advanced form of deconvolution since the randomization pattern is controlled.) The talk showed some impressive text to image simulations used by an animation studio!

And then my friend Arnaud Doucet continued on the same theme, motivating by estimating normalising constant through annealed importance sampling [Yuling’s meta-perspective comes back to mind in that the geometric mixture is not the only choice, but with which objective]. In AIS, as in a series of Arnaud’s works, like the 2006 SMC Read Paper with Pierre Del Moral and Ajay Jasra, the importance (!) of some auxiliary backward kernels goes beyond theoretical arguments, with the ideally sequence being provided by a Langevin diffusion. Hence involving a score, learned as in the previous talk. Arnaud reformulated this issue as creating a transportation map and its reverse, which is leading to their recent Schrödinger bridge generative model. Which [imho] both brings a unification perspective to his work and an efficient way to bridge prior to posterior in AIS. A most profitable morn for me!

Overall, this was an exhilarating workshop, full of discoveries for me and providing me with the opportunity to meet and exchange with mostly people I had not met before. Thanks to Bob Carpenter and Michael Albergo for organising and running the workshop!

a journal of the plaid [shirt] year

Posted in Books, Kids, Mountains, pictures, Travel, University life with tags , , , , , , , , , , , , , , , , , , , , , , , , , on August 1, 2022 by xi'an

Read The priory of the orange tree, bought in one of the many Montréal bookstores [where I could have purchased many more books!] This fantasy novel was a Goodread fantasy recommended read, plus a NYT best-seller and nominated for some fantasy award, but I am quite surprised by the enthusiastic support. Indeed, I found the book had a very shallow and predictable scenario, with most of the tropes of the genre (e.g., ninja-like fighters, heroes uncovering long-lost magical artefacts, , super-evil entity about to return to life/power, a few predestined characters saving the Universe). Unrealistic events, all-too-convenient coincidences, with little efforts put in the construction of the world, of the magical rules, or of the political structure there. The second half was particularly bad.

Enjoyed very much my week in the Plateau part of Montréal, with the green spots in from of every house, the density of shops (and not only restaurants), and the fantastic network of BiXi stations that made travelling around so easy and essentially free! (Glad I brought my 661 helmet from home, even though it attracted many questions during the conference!). And lived essentially on (Saint-Viateur) bagels and (Kinton) ramens. With a funny linguistic incident when I ordered a bagel [which I pronounced bah-gael in the Parisian way] in a bakery and was offered a baguette!

Watched The Chase, an improbable but funny Korean film about a grumpy old man uncovering a serial killer, helped by a former cop escaped from a psychiatric facility. Given that the heroes were mostly senior citizens, this made for a welcome major change from the series I usually watched. Also came by chance upon the 2003 Japanese anime Tokyo Godfathers, which I found amazing, despite my rare foray into anime! A most unconventional Christmas movie, to watch in July or any other month.

summit of the gods

Posted in Books, Kids, Mountains, pictures with tags , , , , , , , , , on November 17, 2021 by xi'an
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