Interesting Week

A lot happened during the last week. I learnt flash, flex, action script 3. I don't know everything... But I did get a good glimpse of the whole. It was a lot of fun trying to solve my brother's problem, which consisted in trying to command some light software using a flash or flex interface. It is not completely solved yet. But we are getting close to it. I will also write a few important things I noted while looking for solutions for the problem. There are two types of problems:

• network problems with TCP/UDP broadcast
• flash/flex sandbox security issues

Performance according to Martin Fowler

Martin Fowler is well known for his work on refactoring and software engineering. In his very good book: Martin Fowler: patterns of enterprise application architecture. Addison Wesley 2003. he has some discussion of performance which usually cover the following issues:

• response time
• responsiveness
• latency
• throughput

A number of measures of a system are good indicators for the performance of a system regarding these issues:

• the load
• load sensitivity
• efficiency
• capacity

To make these notions clear, it is important to have some definition:

response time

the time it take to a system to process a request

responsiveness

the time that the system takes to acknowledge a request

latency

the minimum time that the system needs to perform any task even if the task has nothing to be done

throughput

how much work can be done in a given amount of time

We define the measures presented above:

load

how much strain are put on the resources (for example how many users ( or processes ) are logged on (or running)

load sensitivity

an indicator of the variation in the response time depending on the load

efficiency

the efficiency is the performance (i.e, either throughput or response time) divided by resources

capacity

indicate the maximum effective throughput or load for the system

In order to discuss performance, he also describe two kind of processing power scalability, i.e how good a system reacts when the size of the system grows in processing power. Adding more processing power to a server is an example of vertical scalability (or the system is scaled up), where as adding more servers is an example of horizontal scalability (or the system scales out).

What's the ack is that ?

Well! as I was looking at the programs I was updating on my fedora 9 box. I fell upon the program ack. I had no idea what it was so I ran rpm -qi ack... And it told me that it was a kind of grep replacement. It seems to be faster than grep in most cases. Some people tried it out it seems. Though some other seem to disagree.

One of the advantage of ack is that it allows to select more easily the type of files to be checked. So I guess I will have to take a look at it....