Stefano Tommesani

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GPGPU performance on switchable graphics notebooks

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Many notebooks on the market feature switchable graphics, that is, a notebook with an Intel CPU with built-in HD Graphics technology, as well as an additional AMD HD Radeon GPU or nVidia GeForce GPU. During normal usage, just the Intel HD Graphics is enabled, as it consumes less power, and the high-performance AMD or nVidia GPU is enabled only when 3D intensive applications are started.

When developing a GPGPU application, in this example using C++ AMP with Microsoft Visual C++ 2012, you must check that the high-performance GPU is running your GPGPU kernels, or the resulting performance will be so poor, that you will wonder what the hype about GPGPU is all about. To ensure that the high-performance AMD GPU is running your code, right click on the desktop and click on Setup switchable graphics


Unit testing with Visual C++ 2012

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The article related to multi-threading and SSE2 optimizations (you can find it here) uses a quick-and-dirty way to check if the optimized code is correct, i.e. it runs an iteration on a given input image with a reference serial code, stores the resulting output image, runs an iteration of the optimized code on the same input image, checks if the output image matches that obtained with the reference code. This is a valid approach, but the location is clearly wrong: even if we are writing a demo application, the testing code should be separate in unit tests that can be automated and repeated before check-ins and builds. It's time to modify that code to use the awesome support for unit testing contained in Microsoft Visual C++ 2012.

screen shot of unit testing with Microsoft Visual C++ 2012

Last Updated on Thursday, 25 April 2013 13:59

Different types of parallel loops with Intel TBB, SSE2, SSSE3 and Visual C++ 2012

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This is not the first article on this site that discusses how to use the Intel Thread Building Blocks library to spread the computation of an image-processing kernel over multiple threads: the article named "Multi thread loops with Intel TBB" showed how to do it with Intel TBB 2.x. However, due to the enhancements of Intel TBB 4.x, and the availability of C++ 11 compliant compilers such as Microsoft Visual C++ 2012, it is now possible to write more compact and easy to understand code than before.


Last Updated on Wednesday, 01 May 2013 14:06

Further multi-thread processing with Delphi

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In a previous article named "Easy multi-thread programming Delphi", the AsyncCalls library was used to process multiple images at the same time. However, the processing of every single image was still strictly serial, even if image processing kernels are quite easy to accelerate spreading the load over multiple threads.

In this article we will see how the OmniThreadLibrary can be used to split a simple image processing kernel across multiple threads.

procedure TProcessedImage.EffectBlackWhite(Bitmap : TBitmap32);
var x, y : integer;
    Color : TColor32;
    Red, Green, Blue : Cardinal;
    Gray : Cardinal;
    for y := 0 to Pred(Bitmap.Height) do
        for x := 0 to Pred(Bitmap.Width) do
            Color := Bitmap.Pixel[x, y];
            Red := (Color and $00FF0000) shr 16;
            Green := (Color and $0000FF00) shr 8;
            Blue := Color and $000000FF;
            Gray := (Red * 299 + Green * 587 + Blue * 114) div 1000;
            //Io=(0.299Ri + 0.587Gi + 0.114Bi)
            Bitmap.Pixel[x, y] := Color32(Gray, Gray, Gray);
Last Updated on Monday, 22 April 2013 15:45

Facebook authentication with Friend Watchdog

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This article is a description of the integration of Facebook authentication inside Friend Watchdog. It is not meant to be an introduction or a description of Friend Watchdog's features. Please click here for more information about Friend Watchdog.

Why authenticating on Facebook with Friend Watchdog

After authenticating on Facebook, the timeline in Friend Watchdog will contain not only the status of your friends over the past week, but also their activity on Facebook, such as what they posted on their wall, giving a broader overview of what they are doing on Facebook.


Please note that

  1. enabling the Facebook authentication is optional, and it is not necessary for the main purpose of Friend Watchdog, that is checking when your friends are online
  2. the data obtained with the Facebook authentication is not stored anywhere, not in your computer nor in the Friend Watchdog servers
  3. the data obtained with the Facebook authentication is not sent or distributed in any way, so all the updates shown in the timeline are not transmitted to the Friend Watchdog servers

Last Updated on Monday, 15 April 2013 14:22

Friend Watchdog free software for Facebook and Skype

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Friend Watchdog is now offline. There are several technical reasons for this choice, the first one being Microsoft dropping support for the chat API in Skype, the second one being Facebook changing the behaviour of their chat servers. But the most important reason is that a lot of people finally became aware that posting data on social networks is really a security risk, any criminal network can develop a system like Friend Watchdog to gain a disturbing insight into day-to-day life of their contacts. Friend Watchdog was designed to be limited in aggregating data about users, for example the FourSquare integration was never published as I felt it was too dangerous, but I am confident that there are similar spiders grabbing and presenting exactly this kind of information. So, as Friend Watchdog was meant to be a wake-up call to users of social networks, I think that the target was achieved, and it's time to turn it off.

Now I know what you did last monday

Friend Watchdog monitors the state of your friends on Facebook and Skype, stores the status changes on remote servers, and lets you check when your friends have been online in the past week.

Please note that you are sending status updates only when Friend Watchdog is up and running, and that status changes from multiple users are merged, so the more users of Friend Watchdog, and the more these users keep Friend Watchdog up and running, the more accurate will be the usage stats.

Facebook status and posts on Facebook wall in the past week


Your privacy is safe

Why should you trust Friend Watchdog? Here is why:

  • your Facebook account is NEVER sent to our servers, it is stored in encrypted form only on your computer, and it is used to access your Facebook account from your computer only. There is no way that we can access your Facebook account!
  • we do not know who your Facebook and Skype friends are: the names of your friends are salted and hashed with SHA1, and only the hash is sent to the servers, so that we can distinguish between different friend names but we cannot retrieve friends' names from the hashes. For example, an Facebook username such as "stefanotommesani" generates this unique hash code: CDE381A6C6AD22E844263908022D40C4FE634C37. This hash code uniquely identifies the given Facebook username, but there is no way to go from the hash code back to the Facebook username, so the names of your friends remain private, and only you can see them
  • once you allow Friend Watchdog to connect to the Skype application running on your PC (so that you don't even have to tell Friend Watchdog about your Skype password), it only reads the list of Skype friends and their online status, and that is the only information that is being monitored, always using hash codes to encrypt real names so that your privacy is safe
  • the real names of your friends never leave your PC, only the hashes, that is the encrypted names that cannot be transformed back into the real names, are sent to the servers
  • no need to register, no need to open an account, no need to pay anything, just download the software and run it on your PC
Cloud-based software architecture
Safety of Facebook and Skype
Last Updated on Saturday, 07 December 2013 11:17

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