First GSoC Weeks!

Here we are! The first amazing and intense GSoC weeks for the Shogun Toolbox Organization are ended and my first GSoC blog post is here!

Majestic Progress Bars

My first objective was to implement and create a new progress bar which would substitute the old macro SG_PROGRESS, which was used to display elapsed time of algorithm’s execution. The new progress is a simple header only file and it was made to work with single or multi-threaded application (e.g within OpenMP’s #pragma). It is also compliant with Windows terminals.

Here below some use cases:

// Create a progress bar object
auto pb = progress(range(0,10));

// Main Loop
for (int i=0; i<10; i++)
    // Magic stuff
// It can be used also with the new range-based for loop
// introduced with C++11 standard.
for (auto i: progress(range(0, 10)))
    // Revolutionary code

Moreover, you can do also much complex things by exploiting the power of lambda expressions! Let’s say you have a complex for loop with custom endings conditions. With progress, you can write it easily this way:

int condition=1;
for (auto i : progress(
    range(0, 10),
    [&]{ return condition < 5;})
     // This will stop when condition >= 5;

If you arrived here, it means you’re really interested in what I’m saying. Great! You earned a gif!


Some Smart Pointers…

The second task I started was focused on replace the SG_REF and SG_REF macros used all over Shogun codebase to do memory management with the Shogun’s custom smart pointer Some.

In contrast with standard memory management (provided by STL instrument like std::shared_ptr, std::unique_ptr), in which the reference counter is stored outside the object, each of Shogun’s classes maintain its personal counter.

There are two methods, called ref() and unref(), which take care of incrementing/decrementing the object referece counter. These methods are called by SG_REF/SG_UNREF macros.

CGaussianKernel k = new CGaussianKernel()
SG_REF(k);      // We increase k's counter
// We do something with the kernel
SG_UNREF(k);    // We decrease k's reference counter and if it is
                // less than 0, k will be deleted

Of course this is not an easy way to deal with memory management. I can assure you that placing one of these macros in the wrong place will surely lead to errors and unexpected result (which can become REALLY hard to fix).

With the Some pointer, things will become easier for the developers. Some will take care of memory management, by decreasing the reference counter (and deleting the object) when it is not used anymore (e.g when it goes out of scope).

Some<CGaussianKernel> k = some<CGaussianKernel>();
// Boom. Memory management done.
// When k will go out of scope, the Some destructor
// will free the memory occupied.

Merged PRs