October 27, 2013

some setup notes

zsh Zsh is an amazing (mostly) drop-in replacement for bash. On OSX, just run > brew install zsh You also want to install oh-my-zsh. I went a little crazy with plugins. My list is: plugins=(autojump brew git git-flow gnu-utils gpg2 osx textmate zsh-syntax-highlighting history-substring-search) SSH I ssh a lot. So I have a bunch of host entries in my .ssh/config file. Each looks like: Host [shortname] Hostname [hostname] User [username for hostname] IdentityFile [my home directory]/.

October 23, 2013

overly-ambitious-isqo and the design of numerical codes

I have finally released the overly-ambitious-isqo project on github! I wanted to call out two particular design concerns I had. rich language My first goal was to try very hard to build up the C language to very succinctly express the main algorithm in src/isqo_functor.cpp in extremely rich language. It seems like numerical code is typically implemented with loops like for (int i=0; i<N; i) and method calls like deltal(xhat, mu).

October 17, 2013

a really simple iterative refinement example

I wanted to have a quick example of what iterative refinement is and looks like. Suppose you wanted to solve the (very simple!) problem of solving 5.1x=16, without dividing by decimal numbers. (Yes, this is a bit contrived–I’m not sure why you would be able to divide by an integer to get a decimal, but not divide by a decimal to get a decimal. Bear with me.) The standard way would be, of course, to simply evaluate x = (5.

September 20, 2013

C/C++ Values, Pointers, and References

I had an embarrassing realization: While C does have an address-of operator, it does not include reference variable or pass-by-reference syntax. It’s embarrassing because I should have realized that it was a C++ invention; I guess some of my “C” code actually really has been C++ code. For future reference, here’s the current summary of my understanding: var *var &var int xv=3; value invalid memory location of value int *xp=&xv; memory location value memory location of pointer.

August 19, 2013

Numerical Development on OSX (in the Command Line)

I’ve been working on C implementations of my research projects, which can of course be a perilous project. I’ve found some tools that make it hugely, hugely better. Homebrew You can’t do a list like this without mentioning homebrew. You want homebrew instead of MacPorts or Fink or bailing twine and chewing gum or whatever else you were thinking about using. Just do it: You can find the homepage at brew.

July 31, 2013

spring-mass visualization

I’m working on a paper about an algorithm for hotstarting nonlinear program solves; one application of this might be in the realm of nonlinear model predictive control. In these types of models, we first define the physical equations for the system under consideration. They are subject to some control parameters, which are just a mathematical representation of the input we could give the system. We also define an objective–something that we would like to minimize(usually something like time or energy).

July 30, 2013

python decorators

I came across something that I think is actually pretty neat. Python supports ``decorating'' functions, which lets you define behaviors that essentially wrap around a given function. The benefit is that you can write a simple function and decorate it to do something fancier. I realized I wanted to do this with a simple timing output. Say my function was just something really simple like def f_plain(x,y): print("x + y = {}".

June 25, 2013

better matlab email notifications

One of my officemates asked me how I did my MATLAB email notifications. I had originally done it here. Of course, the machine we work on most didn’t support a mail or msmtp command, so I found an SMTP script, which worked okay, but frustratingly also required Python. On a bit more sleep, it finally occured to me that MATLAB might have an email script. Turns out, it does. I wrote a little wrapper script around this to abstract out some of the email details.

May 15, 2013

org-mode emacs to track mileage

I’ve been trying out emacs org-mode lately for keeping track of everything. One thing that seemed worth tracking is the mileage the new Focus gets. Turns out that org-mode supports a kind of spreadsheet, so I made a quick little video demo on how I use it:

April 10, 2013

Getting really fast at LaTeX

Taking LaTeX notes in real time is one of my favorite useless party tricks. I started developing my techniques during the last year or two of undergraduate work at University of Washington, and was extremely good at it by the end of coursework at Northwestern. There are several keys to taking LaTeX notes in real time: Know LaTeX. Shortcut appropriately. Type keystrokes quickly. One keystroke re-renders. Type fewer keystrokes. Type fewer “strange” keystrokes (backslashes, curly braces, etc) Re-renders should scroll to your current location in the text.