Shell and Linear Algebra blogs

Some links which are useful to explore for beginners.

Bash Scripting : AboutLinux
Awk One Liner : here
Linear Algebra :here
Unix One Liner :here
Node.js :here

Recovery Mode without grub

 1)After start booting : Ctrl + Alt + F1 --> Recovery Mode
 2)To reboot from terminal : sudo reboot

Tomcat - java.lang.OutOfMemoryError: PermGen space problem

When i run tomcat, sometimes i got JVM out of memory. This is due to insufficient tomcat memory allocated.

Solution
Steps :
1)Open catalina.sh in specific tomcat. tomcat/bin/catalina.sh
2)add in JAVA_OPTS value: -server -Xms512m -Xmx1024m -XX:NewSize=256m -XX:MaxNewSize=256m -XX:PermSize=256m -XX:MaxPermSize=256m -XX:+DisableExplicitGC
3)Restart tomcat again

For more you can refer Here

Octave 3.4.3 Installation Ubuntu

1) Sudo apt-get install build-essentials
2)Download octave3.4.3 from Here
3)Untar it, and then install gfortran using sudo apt-get install gfortran
4)apt-get install octave3.2-headers [For building dependencies]
Or
apt-get install libblas-dev libatlas-dev liblapack-dev
5)sudo mv /usr/bin/gfortran    /usr/bin/gfortran.ORG
6)sudo ln -s /usr/bin/gfortran-x.x   /usr/bin/gfortran [create a soft link]
7)Create enviornment variables :
   - export CC=/usr/bin/gcc-x.x
   - export CXX=/usr/bin/g++-x.x
8)./configure in octave folder
9)make [it will take around 30 mins]
10)./run-octave
11)make check
12)sudo make install
13) make
14)make clean
For more Info check here

Useful Links for Algorithms and Puzzles

Coding Contest :

1>Code Chef : Initiative of Directi
2>AI challenge : http://aichallenge.org/problem_description.php
3>ML coding contest : http://www.kaggle.com/ [Best]
4>Heritage Health Prize :  Data analysis contest http://www.heritagehealthprize.com/c/hhp


Algorithms :

1>Carrer Cup [Blog /Pdf]
2>Geek for geeks [best]
3>Crack The Interview [Pdf]
4>Freshers world

Puzzles :
1>Gurmeet singh puzzles :Delightful Puzzles
2>Cracking the code : http://shashank7s.blogspot.com/p/stacks.html