Algorithm Selection

A couple of weeks ago, we were asked to write two different approaches to adjusting the volume of sound samples. The two approaches we were asked to write was:

• Scaling the values of sound sample by multiplying value by a scaling factor.
• Scaling the values of sound sample by multiplying value by a scaling factor and storing it into a lookup table. So, when the program needs the data it will provide it from lookup table until the scaling factor isn’t changed.

To analyze the performance I’ll be using the Archie system (CDOT's ARMv8 - AArch64) and Xerxes system (CDOT's x86_64). I’m going to be using data type int16_t (16 bits) to represent a sound sample and providing 5,000,000 samples which adds up to 10MB of sound sample’s volume to adjust.

To calculate the performance of each approach I first made a dummy run of the program to get its performance without adjusting the volume. In this the program just creates a 10MB of sample data and prints out all its values.  Then I calculated the performance on each approach of volume adjustment. I made five runs on each approach on each system.

Performance on Archie:

Tests	1	2	3	4	5
Dummy run	10.86s (11392 KB)	7.79s  (11328 KB)	10.82s  (11328 KB)	7.49s  (11328 KB)	10.82s  (11392 KB)
Multiplication	9.54s  (11328 KB)	9.50s  (11392 KB)	12.15s  (11392 KB)	9.06s  (11392 KB)	11.99s  (11392 KB)
Lookup Table	7.96s  (11584 KB)	11.39s  (11584 KB)	7.37s  (11584 KB)	11.39s  (11648 KB)	11.42s  (11584 KB)

Performance on Xerxes:

Tests	1	2	3	4	5
Dummy run	0.86s  (12416 KB)	0.85s  (12360 KB)	0.87s  (12368 KB)	0.85s  (12364 KB)	0.93s  (12392 KB)
Multiplication	0.92s  (12308 KB)	0.90s  (12416 KB)	0.91s  (12316 KB)	0.91s  (12424 KB)	0.86s  (12472 KB)
Lookup Table	0.93s  (12448 KB)	0.95s  (12496 KB)	0.92s  (12524 KB)	0.94s  (12608 KB)	0.92s  (12540 KB)

As you can see results from Archie system is inconsistent in terms of run time, but the memory usage of the program is consistent and Xerxes system is providing consistence run time and memory usage. By looking at these stats we can say that Xerxes system is faster in performing these tests.

The average run time on Archie system is: 9.556s on dummy run, 10.448s on multiplication, and 9.906 on the lookup table; and the average run time on Xerxes system is: 0.892s on dummy run, 0.900 on multiplication, and 0.932s on the lookup table. Using the average we can calculate the run time of adjusting volume on Archie system is: 0.892s on multiplication method and 0.350s on lookup table; and for Xerxes system is: 0.008s on multiplication method and 0.04s on lookup table method. You can also see that Xerxes system consumes more memory than Archie system. So, based on these results I would say that the approach of adjusting volume depends on the system you are using.

File Transferring

A couple of days ago I wanted to transfer some source files on Archie (CDOT's ARMv8 - AArch64 system) and Xerxes (CDOT's x86_64 system) machines and run my program and analyze the result between these systems. When I regularly connect to these systems it uses my private key generated on my Linux machine as password and provides me access to Archie and Xerxes systems. I was having problems making a file transfer to these systems but after some research and help from professor (Chris Tyler) I learn few more interesting things as well.

Transferring file to Xerxes system was easy, If I’m on College’s network then I can just use “scp test.cpp (filename) (username)@xerxes.internal.cdot.systems:(destination)”. Xerxes server is only access able from Seneca’s network so, if you want to connect to Xerxes server from outside you can use other system which can be access able from outside like Archie and Matrix and using that you can connect to Xerxes system but you have to transfer the private key to these systems. Also after connection name if you do not include “: (destination)” the file will not be transferred it will just make copy of that file and put it in current directory with connection name as file name.

When you want to transfer file on Archie machine it’s little complicated because you have to specify the port number. Archie machine connection is set up to connect via different system so you have to connect to it using “ssh –p 2200 (connection name)”. Also for Archie there are two different connection names, one for connecting from outside College network (ehl.cdot.systems) and another for connecting from within Seneca network (ehl.internal.cdot.systems). so if you want to transfer file on Archie system you can use “scp –P 2200 test.cpp (filename) (username)@(connection name either internal or external):(destination)”. Also keep in mind that because Linux is case sensitive the scp command uses capital ‘P’ to specify port number.

If you have your private key protected by a passphrase and every time you want to connect to different machines you use your private key and you have enter your passphrase to unlock private key. If you use ssh-agent and add your private key to that agent and by doing that you can connect to multiple servers without entering your passphrase and also keeping you private key secured at the same time. You can do that by entering command “eval $(ssh-agent)” the add your private key by entering “ssh-add ~/.ssh/id_rsa (path to private key)” and you will be prompt to enter your passphrase and enjoy.

Finally, there are many other services you can use to transfer files like: ftp, sftp, filezilla (GUI), wget, and more.

Open Source Community

There are a lot of open source software’s out there and a lot of programmers come to gather to make that software. One of the open source software I looked at was Front Accounting which is licenced under GNU General Public License. This license basically allows users the freedom to run, study, share, and modify the software

How to Contribute to Software

To begin contributing to this software you can head over to Front Accounting’s wiki page which gives you the information on the project, like: different ways to obtain project source code, links to forums/discussions, and more.  On their forum page you can find out the project broken down into many little pieces and how are they planning to implement it, place for reporting bugs, wish list, modules discussions, and even job offers.

Bug Tracker

On the forum page there is a place to report bugs and people discuss on how to fix these but the primary system is Mantis bug tracking system which is allowed for registered users only but you can make an account easily. Mantis system is an issue tracker that provides a delicate balance between simplicity and power.

Bug fixes/Patches

Eventually someone who will be fixing bugs will be discussing their progress and on forum or on the Mantis bug tracking system and many people would be testing to see if the patch fixes these problems or not and according to these results that patch will be used in project.

Community

The community can jump into discussions or issues and provide solutions. The source code is made available on GitHub, SourceForge, BitBucket and with different versions/modules. On the Forum page there are over 7,000 registered users and they have discussed in over 4,000 topics about Front Accounting software.

Second open source software I looked at was Spam Assassin licenced under The Apache Software Foundation. Apache license agreement allows users the freedom to run, study, and share. The licence agreement must be sign if you want to modify the software.

How to Contribute to Software

To begin contributing to this software you can head over to Spam Assassin wiki page where you can learn about the software, join to mailing list, look at reviews, and etc. There is also a link for developers where it gives you information about joining to development spam assassin software. You can find information on general rules like coding style, development rules, how to get source code, and etc. You will have to join a mailing list in order to get latest updates on software. Contributors are divided in to different roles, like: contributors (anyone can provide feedback, submit bug reports, or submit patches), committers (a committer is simply an individual who was given write access to the code base), PMC Members (the project management committee is responsible for managing a project), and finally there are users who uses the software.

Bug Tracker

There is a forum page where all the problems are reported and discussed by developers. You have to be registered to report bugs and collaborate on solving these problems.

Accepting Patches

Eventually someone will come around to fix the bugs reported in software, they will be discussing their progress on bug tracker system and when they are done they will be submitting it. According to development mode page some one will be reviewing the code and after that they will be testing it.