Karin Schnass
University of Innsbruck
Dep. of Mathematics
Technikerstraße 13
6020 Innsbruck

Tel: +43 512 507 53881

Optimisation Principles, Models and Algorithms for Dictionary Learning

Hello creative brains!

No open jobs for now but we will probably start hiring again once we know whether we have money until '21 and how much (late'18).

In the meantime enjoy browsing and if this gets you mega-super-motivated for dictionary learning don't hesitate to contact us. We can probably still arrange a research visit.

If have you most of the skills in linear algebra, probability theory and/or functional analysis and all the interest in dictionary learning but don't have a master's project yet, come for a chat (msc)!

Finally, if your head is still spinning from the introductory lectures but you think that messing around with images could be fun, check out our bachelor projects (bsc)!


The mid-evaluation report is submitted! Now we have to wait till November to know if we get to keep our jobs, so motivation is soaring. Actually it's not as bad as expected. Things being beyond our control turns out to be quite liberating. Flavio found a bug and now all simulation results are much better, Marie is writing up a first version of results for approximate sparsity level. Karin, after cleaning her code for the adaptive dictionary learning toolbox, and adding pseudocode to the manifesto, has sharpened her pencil to go after her favourite dragon - the elusive average case analysis of OMP.

It is 47 pages long or - to sound more attractive - 4 pages per figure. Behold, the new paper on dictionary learning - from local to global and adaptive, which is - we are absolutely unbiased here - pretty cool, because apart from the theory getting closer to what we see in simulations we can do adaptive dictionary learning, meaning automatic choice of sparsity level and dictionary size. Toolbox soon, alas we first have to submit the evaluation report. Also for greater enjoyment the mfiles should better be converted to humanly readable format.

Michi submitted his thesis, found a job and went on holiday before leaving us for good in April. The others are trying to cope each in their own way, Marie near tears, getting a new tattoo, Karin in denial, going to Paris and Oberwolfach , and Flavio, in compensation, doubling the job submissions to the computing cluster.

We have a date!!! The mid-term report needs to be submitted by the 9th of May. So full throttle till the 9th and lethargy from the 10th on.

The nightmare paper is accepted (pdf), long live the nightmare paper!! Actually the other nightmare paper has also been improved, if you want to verify that we really have a fast analysis operator learning algorithm, have a look at the updated toolbox. It's also been resubmitted as a test to see if we will ever do a review for TSP again - couldn't in good conscience force our reviews on them, since they are probably as bad as our papers.

Except for Marie everybody is busy doing the millions of simulations. While revamping the masked dictionary learning paper, Karin is starting to wonder if it's not time to ask the FWF about the prolongation of the project as in continued salaries for all of us but also meaning the mid-term report is due, meaning we should really finish all those papers, ...on second thought, better stay blissfully ignorant until next year.

Family trouble: Flavio is blocking the cluster with simulations and Michi is pissed off because he wants to make just the last simulations to finish the paper in November. Karin in her endless wisdom is calming the waves, saying don't worry finishing in December is already ambitious and in any case nothing's going to happen over Christmas.

Moral is low, Michi only managed to nail down convergence to the generating operator with some help from the oracle support fairy. Disgusted with analysis operators he went to cry with Papa Felix (Krahmer). Karin is finding out how much she does not know about probability, Flavio is trying to make horribly complicated results look simple and Marie is suffering her first PhD year in silence.

Nice better step size for learning analysis operators actually leads to better results, ok smarter algorithms lead to even better results even faster, but if you insist on learning analysis operators online that can now be done.

In between holidays, group is driven mad by Karin trying to find the correct cut-off for adaptive dictionary learning, ie. how to distinguish between atoms and rubbish in the case of noisy data. Fortunately after the engineering/cooking approach failed, going back to theory worked, e.g. we have a criterion and sanity is preserved!! We are also implementing the better step size for analysis operator learning and writing up the big paper on compressed dictionary learning - slowly (compare July entry).

Family trip to FoCM in Barcelona!! While Flavio, Michi and Marie were sweating, Karin's brain finally reached operating temperature. List of achievements: pretty talk on adaptive dictionary learning, magic new step size for analysis operator learning, squeezing promise for help with random subdictionaries out of Joel (Tropp), realising yet again that in most talks we know as much as Jon Snow. Also cervical supercooling is now the official reason for slow publishing.

We (Karin, Flavio and Michi) went to SPARS in Lisbon to entertain people with compressed dictionary learning and analysis operator learning, more details here. On this occasion we also witnessed for the first time in our lives left-over-cake at a conference, amazing!!!

Tinkering with theory for nightmare paper went well, so Karin is back to tweaking millions of screws to make it work in practice. Flavio is off to Rennes learning audio dictionaries. Michi is praying for paper acceptance and dreaming of the end of his PhD, while Marie is thoroughly enjoying the misery and self-doubt of her first PhD year.

Michi hit the arXiv submit button! If you can't bear to leave this page to go to arXiv, the analysis operator learning nightmare paper is also available here and we even have a toolbox to play around with!

We hosted the WDI2 workshop, nobody complained so I'd say success! More good news, both our SPARS abstracts were accepted so we (Flavio, Michi, Karin) are going to Lisbon. Eventful month, congratulations to Marie for successfully defending her MSc thesis and officially starting the PhD!! Useful side effect, Michi the older kid got jealous and started to actually write the paper, let's see when we finish.

February - Karin tinkering with theory for her nightmare paper, Flavio exploding the cluster with simulations, Michi on holidays in Cuba and Marie putting the finishing touches on her MSc thesis - nothing much happening - well it is a short month.

Hello World!!!
To celebrate the acceptance of the first cofunded paper [pdf], the submission of the first fully funded paper [pdf], the quasi - completeness of the team and the organisation of our first workshop [wdi2].... voila a website!!!