How to benchmark a C++ code

As the last step of software development you should test the performance of your code. This is a simple example how to benchmark the time consumption of different procedures in a C or C++ code. We will compare two procedures: calculating sinus and exponential values for 5e7 numbers. Let write a code with name test.cpp

#include
#define LIMIT 50000000
void exponential(){
double a;
for(int i=1;

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How to Periodically remove temporary files in Linux

To remove periodically some files from a specific directory you can easily setup a cron entry. Execute in shell

crontab -e

and add

*/60 * * * * find /home/my_home/some_dir/ -name '*.dat' -mmin +60 -exec rm {} \;

where .dat is the suffix of the files and "-mmin +60 -exec rm {}" is the option telling to remove the files with data modified more than 60 minutes ago.

If your crontab uses Vim

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How to Encrypt directories using EncFS

Install EncFS:

sudo apt-get install encfs


EncFS uses the fuse kernel extension, which we need to load into the kernel

sudo sh -c "echo fuse >> /etc/modules"
sudo modprobe fuse


Add yourself into the fuse group

sudo addgroup my_login_name fuse


Log out and log in.
Create your encrypted directory:

cd ~
mkdir .encrypt
mkdir encrypt
encfs $HOME/.encrypt $HOME/encrypt

Press enter few times,

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How to change MAC address of your WIFI or Ethernet card

Open a terminal window and type the following command



sudo ifconfig eth0 hw ether xx:xx:xx:xx:xx:xx


replace xx:xx:xx:xx:xx:xx with the MAC address that you want to change to

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How to Setup Transparent Squid Proxy Server in Ubuntu

This is a short guide how to set up a transparent cache proxy on Ubuntu Server. Basically, there are two reasons why you may be interested setting up a Squid proxy: speed up your web access and save your bandwidth. Let assume that you already set up a Linux gateway using iptables. It is possible to run squid also on Windows but unfortunately it is extremely hard to find a hardware on which

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How to convert CHM to PDF in LInux

1. Install dependencies by running in the Terminal:
sudo apt-get install htmldoc libchm-bin python-chm


2. Download chm2pdf by clicking this.
3. Now extract the downloaded file.
4. Open your Terminal and browse to the folder you extracted and run: sudo python setup.py install


5. You’re done!

Now to use it is very simple:
In Terminal, type:
chm2pdf --book filename.chm
# (Where filename is

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Google To Switch To EXT4

Google is in the process of migrating their EXT2 file-systems over to the modern EXT4 file-system. This was brought up in a JFS benchmarking discussion. Google's Michael Rubin shared that they chose EXT4 after benchmarking it as well as XFS and JFS. Their results showed EXT4 and XFS performing close to one another, but with it being easier to upgrade from EXT2 to EXT4 rather than EXT2 to XFS,

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How to disable KVM in running kernel to solve errors while running VirtualBox

Issue this following commands as root or with sudo permission

rmmod kvm_intel
rmmod kvm


after that run VirtualBox

To solve the problem permenantly add these commands to scripts that will be executed when system starts like /etc/rc.local

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40,000 processors and 104 TB of RAM Assembled to Render Avatar

As the special-effects-driven blockbuster AVATAR stuns audiences with its lush computer-animated fantasy scenes, a data center in Wellington, New Zealand, has played a backstage, but vitally crucial role.

New Zealand-based visual effects company Weta Digital (www.wetafx.co.nz) was able to manage the intense streams of data required to render the cutting-edge 3D animation used in movies like I,

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[ ubuntu ] Quick and Dirty method to remove a corruted partially installed package

This method can be used when  commands related to aptitude or dpkg is not able to solve the problem


If you have tried everything else, a last resort is this.

1. Backup your /var/lib/dpkg/status file NB You MUST do this first, becuase if you lose this file, your system is hosed.

2. In a terminal, type in the following command: sudo gedit /var/lib/dpkg/status

3. The errant package seems to

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How to enable file and folder listing in apache

Option # 1: Using Apache config file

Add directory option to Apache configuration file /etc/httpd/httpd.conf or /etc/apache2/apache2.conf:
# vi /etc/apache2/apache2.conf

Add following code:

Options Indexes FollowSymLinks

Save and close the file. Restart Apache:
# /etc/init.d/httpd restart

OR
# /etc/init.d/apache2 restart

Option #2: Using .htaccess Files with Apache

You can place config

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