June 2014 - firedrake - imperial.ac.uk

trying to set up nonlinear problem
by Cotter, Colin J 12 Jun '14

12 Jun '14

Dear Firedrakers, When I run the following script: https://gist.github.com/anonymous/32edd8c9c1614c1e2b67 I get: ufl.log.UFLException: All terms in form must have same rank. This is probably because I don't know how to set up nonlinear problems properly. Can anyone spot what is wrong? cheers --cjc

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latest
by Colin Cotter 03 Jun '14

03 Jun '14

Dear Firedrakers, Latest results, I have just done my first solution of a mixed Helmholtz equation on the extruded spherical annulus (the volume between two nested spheres, i.e. the geometry we need to solve for the atmosphere). This works thanks to: * extruded mesh iterators from Doru * extruded FEM spaces from Andrew * The "Hedgehog" mesh and help on how to use the preconditioner from Lawrence * everything else in Firedrake... See attached for a picture showing the solution a couple of slices through the solution (obviously the resolution is quite coarse!). For those in the know, this is actually using the "shallow atmosphere approximation" which neglects the increase in spherical surface area with radial direction (obviously a bad approximation for this O(1) mesh!). Next step is to use the hedgehog trick to add the curvature terms so that we remove this approximation, and of course some validation tests. Then we'll move on to building an atmosphere model using this setup. Keep up the good work! --cjc

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Seminar on mixed finite elements for wave equations by Rob Kirby 1200 on Friday 13 in Huxley 130
by David Ham 03 Jun '14

03 Jun '14

Hi All, Rob Kirby, of FIAT, FEniCS and Sundance fame, is visiting us next week. He'll be giving what promises to be a very interesting seminar at 1200 on Friday in Huxley 130. I'd encourage you all to attend. (And for those attending FEniCS '14 in Paris the next week, this is very different from his talk there!) Full seminar details are at: http://www3.imperial.ac.uk/newsandeventspggrp/imperialcollege/naturalscienc… Cheers, David -- Dr David Ham Departments of Mathematics and Computing Imperial College London http://www.imperial.ac.uk/people/david.ham

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Fwd: Jan Vitek, today, 2nd June, R: a language for data analytics - ROOM 308 (changed)
by David Ham 02 Jun '14

02 Jun '14

A talk in 15 minutes time which Firedrake people might be interested in. *The once and future R: a language for data analytics* * Prof. Jan Vitek, Purdue* *TIME 2nd June, 11:00* *ROOM 308* Data analytics is all the rage. This talk overviews the state of the R programming language — a language designed by, and for, statisticians and data scientists of all stripes. With millions of users worldwide, R is a success story amongst domain specific programming languages, yet it is also misunderstood. R is both a lazy functional language and an imperative object-oriented one. It emphasizes rigorous mathematical development, yet it has not formal semantics and relies on unstructured reflective operations. It’s design is a puzzle; it’s performance is a tragedy. After conducting a large corpus study, we have gained a better understanding of the semantics R and of its real-world usage. Armed with this information, we have implemented FastR a self-optimizing interpreter for the language that yields an average 7x speed up. The techniques we are exploring are not limited to R but apply more widely to the family of dynamic language that includes JavaScript, Ruby, Lua, Python and PHP. Biography Jan Vitek is a Professor of Computer Science at Purdue University and University Faculty Scholar. Over the years, he worked on topics related to programming languages, their design, use, and implementation. With Noble and Potter, he proposed the notion of flexible alias control which became know as Ownership Types. He led the Ovm project which produced the first real-time Java virtual machine to be flight tested on a ScanEagle drone (he claims no one was harmed). Outcomes of this project include the Schism real-time garbage collector and the FijiVM – a production VM for embedded systems. More recently, Jan worked on dynamic languages, trying to make sense of JavaScript and to design a new language called, Thorn. Nowadays, he spends his time with statisticians and data scientists. Jan believes that his 2012 election as Chair of SIGPLAN was an accident; since has been busy trying to rock the boat to ensure this does not happen again. In his spare time, Jan enjoys organizing conferences and sitting on PCs (over 25 in the last decade). He founded the MOS (mobile objects), IWACO (alias control), STOP (gradual typing), and TRANSACT (transactional memory) workshop series. He was the first program chair of VEE and chaired ESOP, ECOOP, Coordination and TOOLS. He was the general chair of PLDI (in Beijing!), ISMM and LCTES. He may still be sitting on the steering committees of ECOOP, JTRES, ICFP, OOPLSA, POPL, PLDI, LCTES, ESOP. Jan will spend part of 2nd June at IC. Please let me know if you want to talk with him. Sophia -- Dr David Ham Departments of Mathematics and Computing Imperial College London http://www.imperial.ac.uk/people/david.ham

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