Alter Ego! » Computer Science

Multi pull

josemanimala — Mon, 16 Apr 2012 13:50:42 +0000

Suppose I am building a software using ten different libraries which are frequently updated, a nice to have would be git pull all which would download all linked libraries from their origin hosted locations.

Julia CGI Get request example

josemanimala — Mon, 02 Apr 2012 11:23:37 +0000

Adding to the apache cgi example for julia. Here is a small script to handle get requests using the QUERY_STRING environment variable. This example heavily utilizes code examples on CGI using C.
#!/home/jose/JMM/Code/julia/julia


libc = dlopen("libc.so.6")

paramsList = ccall(dlsym(libc, :getenv), Ptr{Uint8}, (Ptr{Uint8},), "QUERY_STRING") matcher = match(r"(.*)=(.*)",cstring(paramsList)) param = matcher.captures if param[1] == "Name" println("Content-type: text/html\n\n") println(strcat("Hello ",param[2])) end

Call the file as shown below.

http://localhost/julia-web/helloworld.jl?Name=Jose

Julia and mysql

josemanimala — Mon, 02 Apr 2012 10:37:29 +0000

Simple mysql client version number example for julia using the ccall library loading interface.

prerequisites.

sudo apt-get install libmysqlclient16-dev

copy the code into a file called dbversion.jl. Please remove the C style comments in the code as they WILL NOT work in julia.

#!/home/jose/JMM/Code/julia/julia


//print the content type header
println("Content-type: text/html\n\n");
//Load the mysql libraries
mysql = dlopen("libmysqlclient")
//call the C library with a pointer return type
mysqlexec = ccall(dlsym(mysql, :mysql_get_client_info), Ptr{Uint8}, ())
//convert the returned pointer to a string.

println(cstring(mysqlexec))

Should successfully print the mysql version number. I am still working on the various aspects of this. Also the above code was for use with apache.

Simple hello world in julia

josemanimala — Mon, 02 Apr 2012 10:09:41 +0000

First off configure apache to handle the .jl file extension and enable exec permissions on the folder

open up the default file under /etc/apache2/sites-available.


directory "/var/www/julia-web/"

                AllowOverride None

                Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch

                Order allow,deny

                Allow from all

directory
AddHandler cgi-script .cgi .jl

Restart apache

sudo service apache2 restart

create a simple file under the path /var/www/julia-web.

jose@meanmachine-jr:/var/www/julia-web$ cat > helloworld.jl #!/home/jose/JMM/Code/julia/julia println("Content-type: text/html\n\n"); println("Hello world");

Change the line in bold to the path to your compiled julia interpreter.

as with any cgi file make sure to give execute permissions to the file.

chmod -R 777 helloworld.jl

That should be it.

Hello world in julia

Julia Lang on Bodhi Linux :)

josemanimala — Mon, 02 Apr 2012 09:36:48 +0000

This is more of an informational log on compiling julia on Bodhi linux 1.3.

The first thing about any linux builds is to make sure you have the linux kernel headers installed for your linux kernel version. I am assuming you already have and hence proceeding to the important part.

Clone the repository.

git clone git@github.com:josemanimala/julia.git

Install the prerequisites.

sudo apt-get install libncurses5-dev gcc-multilib gfortran

I was getting there architecture errors, for which the julia lang website suggests passing the architecture value in the commandline or setting it in Make.inc that comes with the julia archive.

make TARGET=NEHALEM

This should start building julia.

Issues, I was getting build issues with the file ~/julia/external/llvm-3.0/lib/Target/X86/Release/ folder missing some files. To get rid of this, I went into the llvm directory and manually ran make. Once that was completed moved to the julia folder and executed make again. This time it ran to completion without any problems.

Finally.

jose@meanmachine-jr:~/JMM/Code/julia$ ./julia
_
_ _ _(_)_ |
(_) | (_) (_) |
_ _ _| |_ __ _ | A fresh approach to technical computing
| | | | | | |/ _` | |
| | |_| | | | (_| | | Version 0.0.0+1333339897.re491
_/ |\__’_|_|_|\__’_| | Commit e491e6cf9c (2012-04-02 09:41:37)
|__/ |

julia>

Going to look at building web apps in julia next. DB support?

Dead beef: shuffle annoyance!

josemanimala — Mon, 26 Mar 2012 07:42:12 +0000

I love dead beef and its my favorite music player when I am coding. But one thing that annoys me is that dead beef with shuffle on picks a random song when I press previous rather than going to the previous song. Also, I can pause and play with the pause button seems like the underlying api shares function calls.

Dead beef creator thank you so much for this music player.

Cheers,
Jose

Android – Free apps, battery usage, needs a study?

josemanimala — Tue, 20 Mar 2012 08:10:13 +0000

/rant

This is really absurd, they actually needed a study to show that Free ads in android apps would sap the battery?

source: http://www.phonearena.com/news/Study-says-free-Android-apps-can-zap-your-battery-life_id28228

Personal opinion: I would say this was obvious as the ads do use up more battery charge than the applications use, because they are pulling the ads off the internet using http requests which do put unnecessary toll on the battery, which is already using up enough charge to run the app in the first place. But to go on a scientific study and funding for that to me seems a little redundant. To a computer engineer, this fact about battery usage is very obvious.

Sigh! Well, there has to be a way to fund and support Masters projects, but this one is the lamest one I have heard so far.

/rant over

The study could be looking at other complex phenomenon which are using up a lot of battery charge, but highlighting this one fact could seriously be taken in another sense.

Cars with light sensors like phones

josemanimala — Sat, 17 Mar 2012 11:34:52 +0000

Are there any cars out there that have light sensors on them. It would be a great idea for mass market cars. I almost always forget to turn off my cars head lamps.

Google, why?

josemanimala — Wed, 29 Feb 2012 17:22:33 +0000

Google had this nifty feature where, you search for something on the main page (google.com) and then click on one of the tabs for its other services, it would load up the results for the thing you searched for previously on the web.

Now after the web ui updates this is gone! This was a nice to have!
Why google? Why?

Debian Squeeze Dom0 and DomU

josemanimala — Thu, 23 Feb 2012 07:11:19 +0000

This is a quick guide and note myself to create a simple xen vm (domU) on Debian Squeeze.

I am assuming that you have a host running debian squeeze with the base system installed on it. I am using the default ext3 filesystem and not using lvm.

Install the required xen kernel. This is a paravirtualization setup and my processor doesn’t support full virtualization (HVM).

Executing all commands logged in as root. If not please append the sudo command after installing it using sudo apt-get install sudo and then add your user to the /etc/sudoers file using visudo command.

After that proceed to install the xen base system and xen tools. we will use the xen-linux-system meta package to automatically do the basic install.

# apt-get update # aptitude -P install xen-linux-system # apt-get install xen-tools

Update grub to defaultly boot the xen kernel

# mv -i /etc/grub.d/10_linux /etc/grub.d/21_linux # update-grub

Edit the xen domains file as shown below. This is because Xen will save and restore a VM rather than do a clean shutdown, too much HDD resource usage.

vi /etc/default/xendomains


#XENDOMAINS_SAVE=/var/lib/xen/save

XENDOMAINS_SAVE=""

#XENDOMAINS_RESTORE=true XENDOMAINS_RESTORE=false

reboot the machine now to boot into the new kernel.

# reboot

edit /etc/xen-tools/xen-tools.conf to have the below configuration settings at a minimum.

dir = /home/xen install-method = debootstrap size = 4Gb # Disk image size. memory = 128Mb # Memory size swap = 256Mb # Swap size fs = ext3 # use the EXT3 filesystem for the disk image. #dist = `stable` # Default distribution to install. image = sparse # Specify sparse vs. full disk images. dhcp = 1 passwd = 1 kernel = /boot/vmlinuz-`uname -r` initrd = /boot/initrd.img-`uname -r` mirror = `xt-guess-suite-and-mirror --mirror` mirror_squeeze = http://cdn.debian.net/debian ext3_options = noatime,nodiratime,errors=remount-ro ext2_options = noatime,nodiratime,errors=remount-ro xfs_options = defaults reiserfs_options = defaults btrfs_options = defaults

Create the squeeze vm using the xen-create-image command below. I am creating it to use our default dhcp server to get an ip.

# xen-create-image --hostname xen1.local.com --vcpus 1 --pygrub --dist squeeze --dhcp General Information -------------------- Hostname : xen1.local.com Distribution : squeeze Mirror : http://ftp.de.debian.org/debian/ Partitions : swap 256Mb (swap) / 4Gb (ext3) Image type : sparse Memory size : 128Mb Kernel path : /boot/vmlinuz-2.6.32-5-xen-amd64 Initrd path : /boot/initrd.img-2.6.32-5-xen-amd64


Networking Information

----------------------

IP Address     : DHCP [MAC: xx:xx:xx:xx:xx]
Creating partition image: /home/xen/domains/xen1.local.com/swap.img

Done
Creating swap on /home/xen/domains/xen1.local.com/swap.img

Done
Creating partition image: /home/xen/domains/xen1.local.com/disk.img

Done

Creating ext3 filesystem on /home/xen/domains/xen1.local.com/disk.img Done Installation method: debootstrap

After sometime of processing the command will exit as successful.

On my machine I had to comment out the line in the /etc/xen/xend-config.sxp file before I could boot the domain.

vi /etc/xen/xend-config.sxp #(vif-script vif-bridge) (network-script network-bridge)

restart xend

sudo /init.d/xend restart

I started up the domain with the command

# xm create /etc/xen/xen1.local.com.cfg -c

To exit the console once you are done use ^] (ctrl + ]).

Thanks,
Jose