July 4, 2017

Stop Ubuntu from freezing completely with Intel Bay Trail

Ubuntu and Linux kernel seem to suffer from a cpu state bug which completely freezes the system when doing graphics intensive tasks such as playing games or videos. Many processors suffer from this bug including the following Intel processors:

Celeron J1900
Celeron N2940
Celeron N2840
Celeron N2930
Pentium N3520 
Pentium N3530
Pentium N3540

To see whether you have one of the above processor put the following command in the terminal:

cat /proc/cpuinfo | grep 'model name'

This bug can easily be fixed by installing proper Microcode files and changing c-state flag for Linux kernel.

First step is to make sure you have Ubuntu microcode package installed by putting the following command in the terminal:

sudo apt-get install intel-microcode

Then, remove the existing microcode files by running the following command in the terminal as they are not recent:

sudo rm /lib/firmware/intel-ucode/*

After then, install Intel Microcode files by downloading Microcode package from the following site:

https://downloadcenter.intel.com/download/26798/Linux-Processor-Microcode-Data-File

Download the microcode*.tgz file and extract it in the Home folder. Now copy the extracted microcode files to system folder by opening a terminal in intel-ucode folder and running the following command:

sudo * /lib/firmware/intel-ucode/

Now edit the grub file to change c-state kernel flag by opening grub file in /etc folder by putting the following command:

sudo gedit /etc/default/grub

In the grub file under the line containing GRUB_CMDLINE_LINUX_DEFAULT=, add the following intel_idle.max_cstate=2, so the line should look like the following line:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash intel_idle.max_cstate=2"

Now, save and close the grub file and put the following command in the terminal to update boot loader to reflect kernel flag:

sudo update-grub

Done! Now just reboot the system and check whether microcodes are loaded properly by running the following command in the terminal:

dmesg | grep microcode

You should be able to see something like following as output of above command:

[    3.168100] microcode: CPU0 sig=0x30678, pf=0x8, revision=0x829
[    3.168138] microcode: CPU1 sig=0x30678, pf=0x8, revision=0x829
[    3.168445] microcode: Microcode Update Driver: v2.01 <tigran@aivazian.fsnet.co.uk>, Peter Oruba

Cheers!

May 30, 2017

Assigning Binary Value to a Variable in C and C++

If you are programming in C and C++ then you may already know that C and C++ do not have native support for binary literal. So you can not simply write the following statement to give a variable a binary value:

int signal = 1110;

However, C and C++'s bitwise operators such as Left Shift operator << and Or operator | can be easily utilised to achieve binary value assignment like shown below:

int signal = 1 << 3 | 1 << 2 | 1 << 1;

The above statement assigns binary value 1110 to the variable signal. The way it works is the very first expression 1 << 3 creates a binary value 1000, and then the expression 1 << 2 creates a binary value 100 and finally the expression 1 << 1 creates a binary value 10. When all these three binary values are combined using the Or operators we get the binary value 1110 like shown below:

Expression            Binary equivalent
1 << 3            =     1000
1 << 2            =     0100
1 << 1            =     0010
                              1110 (after or operations of three expressions)

One advantage about this method of binary assignment is that there is no need for external libraries and such. The example program demonstrating the above method can be downloaded from the following link:

binary_assignment.c

There is also a convenience functions library called imamB which I wrote recently which can be used for getting binary values of variables as a string and vice versa. To use the functions from imamB all you need to do is to include header and source files from imamB package to your project directory. imamB can be download from the following link:

imamB-1.0.zip

Cheers!
Imam

March 19, 2017

Windows Install and use Python without admin rights

Sometimes it is useful to install Python in a preferred directory other than to a default Windows partition directory. The main reasons for doing this are given below:
  1. Have multiple Python versions and run them as per requirements (use Python versions 2.7 and 3 simultaneously on the same system)
  2. Have Python Interpreter on a portable disk (Python on the go)
  3. Tryout experimental and latest Python versions and Python packages/libraries (leave the default system Python Interpreter unaltered)
Installing Python without admin rights:

Step 1: Download Python installer(msi file) from official website https://www.python.org/


Step 2: Open up Windows Command Prompt where msi file is downloaded and execute the following command,

msiexec /a python-2.7.10.msi /qb TARGETDIR=G:\Python27

Here, TARGETDIR specifies the target folder where Python will be installed.

Once setup is finished you should be able to find python.exe (Python Interpreter) and IDLE (Python Integrated Development Environment) in the G:\python27 and G:\Python27\Lib\idlelib folders respectively.

Step 3: Install pip Python utility script for installing Python packages/libraries by downloading get-pip.py file and executing the following command from the G:\Python27 folder,

python.exe get-pip.py

Step 4: Install Python packages/libraries using pip by executing the following commands from G:\Python,

python.exe -m pip install numpy

Here, numpy is Python package/library name which will be download and installed to Python Interpreter directory by the pip utility. If a package/library is not available in the standard Python pip repository then you can download pip install-able (whl files) Python packages/libraries from pythonlibs and install them by executing following command from G:\Python27, assuming whl files are placed in the same folder,

python.exe -m pip install numpy‑1.11.3+mkl‑cp27‑cp27m‑win32.whl

Cheers!