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Positions Available

Mon, 16 Oct 2017 13:00:00 EDT Postdoctoral positions available immediately

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DMRG++ Tutorial Materials

Mon, 15 Aug 2016 13:00:00 EDT Slides and inputs for the DMRG 101 Introduction to Theory and Practice tutorial have been posted to the below URL. Thanks to all who attended!

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DMRG 101 Tutorial

Thu, 28 Jul 2016 11:00:00 EDT Title: Density Matrix Renormalization Group 101: Introduction to Theory and Practice
When: Fri, Aug 12, 2016
Where: Oak Ridge National Laboratory, Oak Ridge, TN, USA
There is no cost but registration is required. Here is the official announcement and agenda.


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Technical Collaborations

Make sure you have the latest version of this memo.

Version Date: September 22, 2016.

Type of Memo: Informative

Introduction

This is a short list of useful things for our collaboration. It is not intended to substitute communication but to improve its efficiency. Comments and criticisms about this document are welcomed.

Remote communication and Netiquette guide PLEASE READ AND ADHERE TO Netiquette guidelines

Basic Knowledge

Here are basic resources that you need to know well. Links provided are merely pointers, unless otherwise indicated.

  1. Linux platform. http://tldp.org/LDP/intro-linux/html/ In addition, you will need to familiarize yourself with the distribution you will be using.
  2. Basic bash. http://www.tldp.org/LDP/Bash-Beginners-Guide/html/
  3. git. We will use git for all our codebases. There's tons of documentation about git out there: http://git-scm.com/documentation and don't miss the full online book
  4. C Programming Language or Assembly. You need to understand computers from the ground up. Highly recommended: Jonathan Bartlett: Programming from the Ground Up. Bartlett Publishing, 2004. ISBN 0-9752838-4-7
  5. Using make. Just the basic usage, run "man make," or search for a tutorial.
  6. Basic C++. I know C++ is too involved and big, but you will need at least to know the "Hello, world" in C++, that is, the big picture.

Additional Knowledge

Depending on what your work with me will entail, you might need the following additional knowledge.

  1. Code conventions. If you do any programming with me, please adhere to our coding style.
  2. Perl. If you are going to do scripting, it'll probably be done in perl. Feel free to ask why not Python or Ruby or XYZ. But if you don't have an urge to ask the question, then that's OK too. Scripting is not an excuse for sloppy programming or bad style. Adherence to our coding style or modified conventions is expected, as long as possible and practical.
  3. The D Programming Language. We'll start using the D Programming Language as a substitute for perl as soon as gdc is merged into gcc.
  4. C++ templates and C++ virtual inheritance. Please know your C++. C++ is a vast land. Aquiring knowledge in this area could take years. If your assignment includes C++ coding you'll need to know at least C++ templates. How much do you need to know? Make sure you can understand everything in our coding style guide. There's the legal---what can be done---, and moral---what should be done---aspect to C++. You can probably learn both in books. Stroustrup's TC++PL is a must as a reference. Alexandrescu's ``Modern C++ Design'' is excellent for virtual inheritance, and contains a good amount of templates, but perhaps not enough. There is a book by N. Josuttis, I think, that should cover templates extensively. He's got another one dealing with the STL. As for the moral part, let me mention Alexandrescu and Sutton, ``C++ Coding Standards,'' which I used to write CodingStyle.pdf. (Note: You definitely don't need to buy books for the work you will be doing with me. You can find them in the library, or we can use the notes.) In number-crunching codes, performance is an issue, and virtual inheritance (run-time dispatch) needs to be used with care. That's why we emphasize templates (compile-time dispatch).
  5. Using gdb Learn to use the debugger. Because even though it's helpful if you say "I get 'Segmentation fault' when I run the xyz code," it's more helpful if you say "Please consider pulling this changeset that fixes a segfault in the xyz code."
  6. Valgrind memcheck (because sometimes the debugger isn't enough). And it won't be enough more often than you might think. Because sometimes the debugger itself crashes, which you might think comic now, but it isn't when you have a bug to hunt. And sometimes the hardware conspires against you, and segfaults are delayed until they show up in unexpected places, usually at deallocation. In these cases, gdb will likely point you to the wrong place.
  7. Profiling (at least with valgrind --tool=callgrind ) It's helpful if you say "The xyz code runs too slow." It's more helpful if you say "Function f(...) in the xyz code takes too much time." And it's most helpful of all if you say "Please consider pulling this changeset that fixes an unnecessary slowdown in function f(...)."
  8. And there are more valgrind tools...
  9. Code documentation. If you need to document code, please do read documentation guidelines.

Writing and Visualization

This may be important in order to present your work.

  1. LaTeX. If your assignment requires you to write something that (i) will need formatting, and (ii) will require my editing, then please use LaTex or plain TeX. Or ConTeX. Or LuaTeX.
  2. Figures For diagrams, sketches, and plots, please don't use raster images when vector graphics will do. Use of pgfplots and tikz is preferred.
  3. To publish a paper that includes me as an author you must follow requirementsBeforePublication.txt (separate document provided on request), before I can consider your paper.
  4. Talks I strongly recommend latex beamer.
  5. Ray Tracing - https://github.com/mmp/pbrt-v2 - https://bitbucket.org/luxrender/lux

Supercomputers and computer clusters

If you need to run on supercomputers and computer clusters, then you will need the following:

  1. module command In most supercomputers, software is handled by module switches. Please learn them.
  2. Portable Batch System or whatever queue software is used on the supercomputer/cluster. Please learn about queues and walltimes and the difference between nodes and cores. And processors and threads.
  3. LAPACK and BLAS libraries Please try to understand the linker error, 'ld: cannot find -llapack', if you get one. Goes without saying, please learn what a linker is, and you should have anyway, when you read the item ``C Programming Language or Assembly'' above.
  4. Message Passing Interface (MPI) is needed if using distributed memory parallelization.
  5. If using shared memory parallelization please learn and use ``pthreads''. No OpenMP, please.

Linear Algebra Knowledge

This will depend on your task, but most of my work deals with quantum mechanics and quantum field theory in condensed matter. Therefore, to understand the math involved, at the very minimum you will need:

  1. Vector Spaces, Eigenvalues, Eigenvectors
  2. Hilbert Spaces, Dirac Notation (*), Outer Products (*) Dirac notation is only rigorous for finite dimensional Hilbert spaces. But that's all we'll need.
  3. Sparse Linear Algebra (Compressed row storage, Lanczos algorithm)