about this blog

Well I want to make some notes about this blog. At first I have 2 groups of posts on Russian and English languages. Who interesting in various question about interview on software developer positions can grep by interview tag (it's not only my own experience but also experience of my friends and interesting things from the internet). Posts about life behind IT available with life tag. Posts about GPS and navigation avalible with gps tag. I'm working with GPS system from my MSc thesis. and have some experience with DSP algorithms in this field, in this topics I'll try to undercover some interesting things from easy to understand point of the view. Posts about ARM and Linux without any comments. Any other significant things will be added as soon as they appear.

The opinion published on this blog are my own, not necessarily those of my employer.

Octave online

Guys, have you seen Octave online? quite impressive thing, you can store!!! your scripts, it can plot and does symbolic evaluations! Basic Machine Learning, Linear Algebra, Convex optimization, etc courses can be done right without any investment in an expensive software (hello Matlab basic bundle for 5k). w00h00

http://octave-online.net/

Tensorflow in Gentoo virtualenv

Just tried to install tensorflow in Gentoo virtual env with python 3.4 and failed

Back to the Linux or how I debugged silent crash

Just got tired from Mac and decided to move to my old Gentoo Linux. After recompiling world (oh yeah, all from sources) I stuck with SIGSEGV with plot command in Octave (Matlab like math package).

When I tried to plot anything it crashed with SIGSEGV without any obvious reason. So I got to go deeper to fix it. Gentoo supports nice debug options all that one needs is just to enable them
https://wiki.gentoo.org/wiki/Debugging

After that simple
# sudo ulimit -c 99999999
# octave
octave:1> plot(1)

then crash with core in the current folder. Now one need to unwind the stack
# gdb /usr/lib/debug/usr/bin/octave-cli-3.8.2.debug core
(gdb) bt
#0  fl_create_gl_context (g=0x0) at Fl_Gl_Choice.H:102
#1  Fl_Gl_Window::make_current (this=0xc12430) at Fl_Gl_Window.cxx:168
#2  0x00007fc1a5706447 in plot_window::show_canvas (this=0xc11bb0,
    this=0xc11bb0) at dldfcn/__init_fltk__.cc:935
....
#88 0x00007fc1b715a620 in __libc_start_main () from /lib64/libc.so.6
#89 0x0000000000400979 in _start ()

So, I didnt recompile nvidia drivers or my opengl config is bad. I had problems with opengl config, repoint it with eselect opengl and run X11 again.

Problem has solved

Signum JTAG under virtualbox

I'm using Gentoo Linux as the host and Windows (other OSes) as the guest system on my laptop. Some time ago I had to debug ARM device with Signum JTAG but after I installed drivers Windows 7 Device Manager says "This device cannot start. (Code 10)" and no one know how to fix it. I reisntalled it few times, checked old and new drivers but the same. I checked Google but no answer. But I found the solution a little bit later.

Latex and track current version of a document

I wrote a lot of stuff on latex. But any stuff when I have to send it to someone who will revise it every time became pain in the butt, bcoz someone cannot distinguish one version from another. So I made a solution...

How to store Quartus project in VCS (on git example)

Recently I returned to write vhdl code again and faced against problem how to share project among other developers. Of course we need to track any changes and have ability to store project settings (like chip version, pin, etc). Quartus creates bunch of binary and log files, so what should we store and that not.

Book: Safe C++: How to avoid common mistakes

Recently I bought this one. So short review from me.

cygwin and tar

It was really hard battle. I have ant script with some ivy deps. deps in tar format and I use full path to untar it.

android-ndk-profiler tweaks

Recently I need to check our software with profiler. I think everyone knows about gprof and Android as Linux small brother has it too. So android-ndk-profiler really usefull thing, but if one use ndk-build script (standart build scripts from NDK) soon one will see that sources stripped...

Android JNI tips

So many time I thought - wtf with this function signature. Then I found that I can copy signature from .class file. And it was success.

git-svn cheat list 2

Small additional about svn git after this one. Sometimes I have svn repo with huge amount of commits (for now I have svn repo with about 50000 commits), clone it is a REAL pain.

Android native activity with Java classes

For some reason I was need to create native activity and bind Java class into it (btw after I done it I realized that it wont help me).

Android runtime linking

Look here. Android can't load all needed libraries that your .so library need. So you need to load by your hands.

Android NDK and ccache

I decide to add ccache into our project and start to google around this....

git-svn cheat list

I moved to a new company, unfortunately here all most all use svn =( It's pity. So I made some cheat list to use git-svn inside this hell. All story based on Gentoo of course =)

Implements digital filter based on Duffing

As we know Duffing equation works only in analog domain. But in practice it's completely usefulness, we need digital filter which works like Duffing. I try to do it with Volterra series.

Duffing - incoming phase problem

As we all know, Duffing equation go to grate scale period when incoming signal fit to some criterion (sinusoidal and amplitude of resulting signal must be greater than some constant - one can give constant from Lyapunov exponent method). In theory all seems great...

phrack 68, article 11

Interesting article in phrack))) I'd implement some sources

Duffing oscillator with GPS signal

I've read several articles about using chaos theory in GPS. One of them about using Duffing oscillator to detecting periodic signal. As you know GPS carrier is a periodic cosine signal.