Unexpected stuff!

Let’s have a look at this code: int main() { for(int i{0};i<500;i++) { std::cout<<“This is a big number: “<<i*20000000<<std::endl; } } And let’s compile it with g++ using the flag -O3, what’s going to happen? Before answering, let’s have a look at the assembly, shall we? L16: movsbl 39(%ebx), %eax L6: movl %esi, %ecx movl… Continue reading Unexpected stuff!

Almost useless knowledge

Is almost useless because nobody is going to raise yours salary for that! Or maybe someone will?!? Let’s say we ignore all the benefits of all the optimizations our benevolent compiler is going to made on our code, and have a look at what happen when we execute some hundreds of thousands of times two very… Continue reading Almost useless knowledge

Solution space.

Certain problems required us to try all the possible solutions to find the one that best fit the given constraint, a very popular brute force way is to perform a complete search of the solution space by iterating over and over the data and changing each time the input variables. If the problem require to… Continue reading Solution space.

Suffix trees.

An entire post covering both the theoretical part and the implementation is going to take too long, for this reason I’m splitting the material in two parts: A post with some theory introduction, and one post which will be focused on implementation details. The algorithm I would like to show you is the Ukkonen method for… Continue reading Suffix trees.

String searching algorithms comparison.

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Summary for the week.

This was a very long week! Most of my free time I was at the gym or on my combinatorics book learning fancy details about the pigeonhole principle, which is very simple but with large implications in problem solving. The pigeonhole principle basically say that if you want to put three pigeon in two holes,… Continue reading Summary for the week.