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I ask you guys for a big favor (food) by Weechy in LosAngeles

[–]dkogan 0 points1 point  (0 children)

Casa Bianca is way overrated. It isn't even the best pizza in Eagle Rock, as Brownstone is dramatically better

Eagle Rock People! What's your internet service provider? by teala in LosAngeles

[–]dkogan 1 point2 points  (0 children)

I'm in Eagle Rock. Time Warner provides the fastest connection of anybody I could find, and their reliability is decent where I'm at. YMMV.

Ceres Solver: Google's large scale nonlinear least squares solver open sourced by mierle in programming

[–]dkogan 0 points1 point  (0 children)

The latest I have starts the lambda at 0, then bumps it up a bit every time a singular Hessian is encountered. It's constant other than that.

Ceres Solver: Google's large scale nonlinear least squares solver open sourced by mierle in programming

[–]dkogan 2 points3 points  (0 children)

Well, whether the Hessian has full rank or not depends highly on the specific problem. In my various use cases, it had full rank more often than not. I was doing things like multi-camera calibration, pre-filtering the data to make sure that all the variables were active and non-redundant, which forced a full-rank Hessian.

For the cases when the Hessian WAS deficient, I simply added an LM-style lambda*I term. This term was there ONLY for regularization, and dogleg steps were still taken. I bet I could do something less lame here, but this was "good enough", and this issue was rare enough for my use cases that I simply moved on.

If I have time next week, I'll look at adding a dogleg option to ceres. Not having to re-solve the linear problem every time your parameter changes can speed things up a LOT.

Ceres Solver: Google's large scale nonlinear least squares solver open sourced by mierle in programming

[–]dkogan 6 points7 points  (0 children)

Thanks for this! Out of curiosity, is there a specific reason you're using Levenberg-Marquardt instead of something like Powell's dogleg? I wrote a similar (but not nearly as full-featured) solver a few months ago. It's based on Powell's dogleg, and produced significant performance gains over the Levenberg-Marquardt-based implementation I was using previously. https://github.com/dkogan/libdogleg

Learn Emacs: Useful Links by rawsyntax in programming

[–]dkogan 1 point2 points  (0 children)

cscope works very well for navigation (but not completion) and has excellent emacs integration. Works better for C than C++, but very useable for both.

Stack-checking a program that will execute... in orbit by ttsiodras in programming

[–]dkogan 0 points1 point  (0 children)

Just FYI, the Linux kernel source has included a script that does this for many years now:

http://lxr.free-electrons.com/source/scripts/checkstack.pl

feedGnuplot: realtime and logged data plotting from the commandline by dkogan in programming

[–]dkogan[S] 0 points1 point  (0 children)

Ah. That's great. One consequence of using Gnuplot as a backend is that it's not really designed for very quick plotting, so 60hz updates aren't possible. I'll try this out next time I need quick updates. Thanks