AutoLaunch - A new Firefox addon

2009-04-25T23:17:00.000-07:00

Although I'm a Firefox fan, after using Google Chrome for some time now I can say with confidence that although it's a simple browser it has some unique features that make it a great browser too.

What I like about Chrome

One cool feature I like in Chrome is the ability to click on a downloading file, making it automatically launch when the download has completed.

A Firefox addon is born

One of Firefox's most endearing features, as far as i'm concerned, is that I can just change about anything I want with a few lines of JavaScript. The lack of an autolaunch feature seemed like a great opportunity to take advantage of this capability so I spent some time last weekend developing my own version of Chrome's auto-launch feature for Firefox and so AutoLaunch was born.

What does AutoLaunch do?

With AutoLaunch installed you can double click any file, even while downloading, and it will launch once the download is completed. It might not seem like much but I like it and I'm letting you enjoy it for free...

; )

Download it from here: https://addons.mozilla.org/en-US/firefox/addon/11574

Why I like it?

My little addon enables me to launch files from the web with a single click, just as if they'd been stored locally on my computer saving me time, aggravation and unnecessary clicks.

Before we part...

I believe that as we move our digital world online and "The Cloud" becomes the repository we use to encase our lives and souls we must guarantee that we retain the same comfort and accessibility we have in these dreary desktop days. Sometimes it's all about taking care of little details - like double clicking a filename and having it launch...

2009-02-12T15:04:00.000-08:00

How to determine the processor count from a Silverlight web page
By Eylon Yogev.

How can you tell if a computer has more than one CPU without using any special permissions.

Parallel programming requires an easy way to tell if a user has multiple CPUs

Now that most new computes have multiple processors, we are seeing a rapid rise in the usage of parallel programming. Many libraries already supply efficient code for computers with multiple core processors, but how can you tell if the computer you are running on indeed has more than one CPU?

Why is the need to identify multiple CPUs becoming a pressing issue now?

Most programs today are multithreaded. More and more libraries are written for effective multithreaded code, with the assumption that this code will be run on computers with multiple cores. The need to know whether the computer is multi-core is a must, but in certain cases, like web applications for instance, you can’t “ask” the Operating System how many cores it is using outright.

How is this solved “normally”?

When running in the .NET environment, you can easily get the exact number of processors by using the following:

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System.Environment.ProcessorCount;

The bad news is that this property isn’t available for situations where you don’t have permission to ask the Operating System about the number of processors the system is running. This is exactly the situation you are in when you are developing web pages and RIAs based on MS Silverlight or Adobe Flash.

So what to do?

I wrote the following code for determining whether a machine is a multi-core using only the basic operations available in any language and on any platform. The code runs two threads in parallel, and checks if they can really run at the same time.

The main key is to use SpinWait, and although it’s a lot of fun, unfortunately it isn’t deterministic…

SpinWait - The magic key

Roughly defined, a thread’s ‘Quanta’ is the minimum time that the Operating System will dedicate to the thread without making a context switch. It’s usually somewhere between 10 and 15 milliseconds. The code I wrote keeps the processors busy for the amount of instructions given, like creating an empty loop with an increased index; however, unlike ‘Sleep’, this code prevents context switching from the thread, unless it spins in excess of the thread’s quanta.

Note that the OS could demand a context switch due to a system interrupt, or for some other reasons, in which case, the code might report that the computer has more than one core, despite the fact that there is only one core.

Here is the code I use:

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// will indicate that the computer has more than one processor bool moreThanOne = false; // will close the other thread eventually bool toContinue = true; ManualResetEvent m = new ManualResetEvent(false); // open the secondary thread Thread t = new Thread(new ThreadStart(delegate {     // make sure it has time to start     m.Set();     // set the flag while not signaled to stop     while (toContinue)         moreThanOne = true; })); t.IsBackground = false; t.Start(); // waiting for the thread to start m.WaitOne(); // forcing context switch Thread.Sleep(0); // begining of the threads quanta moreThanOne = false; // spin for a short time. Enough for the other thread to set the flag // but still shorter than the quanta Thread.SpinWait(100000); // stop the secondary thread toContinue = false; // return the result return moreThanOne;

The code opens a thread dedicated to repeatedly setting a boolean flag, with the idea of having this thread run on a secondary core, if one exists. In order to ensure that the thread has started and is ready to loop, a ‘wait’ handle is used. The main thread waits for the secondary thread to start, and then calls ‘Thread.Sleep(0)’ to force the context switch. This ensures the next instruction will execute at the beginning of the thread’s quanta. In order to allow the other thread to set the flag on the other core while we are still spinning, we ‘SpinWait’ 100000 instructions. Since the ‘SpinWait’ is shorter than the thread’s quanta, it won’t force a context switch. Now, we can examine our outcome: If the flag has been set during the elapsed time, we know it must have been set by another processor that processed the thread while the other process was busy spinning.

Implementation and usage

I developed the code presented above while I was researching the performance of our http://www.headup.com application. I had discovered we were wasting a lot of time on mandatory locks that, although required, didn’t justify the accrued overhead.

Spinlock – good value, low cost

After some research, I decided to use the ‘SpinLock’ implementation, which utilizes the computer’s two cores to make an efficient lock, in order to boost our application’s performance at, what turned out to be, a very low effort. SpinLock’s secret is that instead of using a system call, the way ‘lock’ does, it uses ‘SpinWait()’ to let the other core release the lock. Of course, if the computer hasn’t got another core, this is useless. So, in order to know whether I could use ‘SpinLock’ effectively, I first needed to validate that the machine I was running had more than one processor. Hence the code above…

Examples and notes

There are several ‘SpinLock’ implementations, I found this one to be particularly nice: http://www.bluebytesoftware.com/blog/PermaLink,guid,fd6ed0d7-2849-4ca1-9619-74cd5713c3c0.aspx
Test my processor detector live for yourself at http://yogil.com/yogi/processors.html. You can see how many processors your computer is running manually by clicking ‘Properties’ on ‘My Computer’ (Windows machines).

Ideas for the future

Because of the risk of false positives, it would probably be advisable to run the method several times and use the most frequent outcome. This will certainly improve results.
By using multiple threads, it should be possible to discover the exact amount of processors, and not merely whether the machine has one or more.

A new Ubiquity mashup with headup

2008-12-14T10:06:00.000-08:00

I've written a really cool post about this. Check it out here: http://blog.headup.com/2008/12/headup-ubiquity-mashup/

Going away

2008-09-24T04:48:00.001-07:00

I'll not be writing in the next month because I'll be traveling in India.
But I'll leave you with this poem I wrote:

(On the melody on Spider Pig)
Javascript, Javascript,
Does whatever a Javascript does.
Can it run very fast?
No it can't, it's a script.

Javascript, Javascript,
Does whatever a Javascript does.
Will it run ever fast?
Yes it will, it will JIT.

Congratulation!

2008-09-11T14:18:00.000-07:00

It's about time I open a blog. Things that I'll tell about here: Silverlight, Firefox, c# and everything in between.

Enjoy.

Yogi's Post