Got stuck with overambitious master thesis I feel that I can get into big trouble very soon. I have been working on my master's thesis in computer science area for about 3 months(out of 6) and still haven't achieved any meaningful result. Although I am working really hard(at least 8 hours per day + some time during weekends), I can't see any hope how to complete this research in remaining 3 months and compile it as a thesis.

The problem is that my supervisor selected very ambitious project for me. Initially, I was a bit scared, but general idea was looking quite meaningful. He promised that "we will be the first who have done this, bla-bla-bla....". In addition to this, he also offered quite generous funding. And I swallowed the bait)

Now, after several months of research, I can claim that the method we are developing looks a bit meaningless(that is why there are no any research on it). Maybe if we dig deeper, this will start making sense, but MS thesis is just for 6 months, I cannot afford doing this research for 1-1.5 years.

So now I am considering dropping out of the project and finding a new supervisor.
Would you recommend doing this? Or, otherwise, how to deal with MS research which yields no results? How this can affect my grade?
Your situation is quite common with MS theses (in the US at least). There are several people who are given ideas from their advisors which either turn out to be dead-ends or take up much more than the allotted time. In EECS, the MS thesis defense is more about displaying your ability to conduct research than having significant results. Clearly describe the problem, your methods, and display preliminary results whether they are significant or not.

As an example, a professor in my university is interested in inverse problems in imaging. Every once in a while he takes up a student for an MS thesis for denoising images. Problem is, nothing really beats an algorithm called BM3D in terms of PSNR for denoising images (except in specific circumstances). So he has had a few MS students who developed a new method which didn't work as well as BM3D but nonetheless conducted meaningful research and successfully defended. Everyone on your committee knows that it is impossible to anticipate whether an idea will actually work before doing it.

Switching topics and advisor halfway through might not work (how do you know that a new idea is doable in time before actually doing it?). Usually, this is best reserved for situations where there are inter-personal conflicts. Assuming that your advisor is looking out for your best interests, schedule a meeting and talk to them about your concerns with the amount of time you have left and what aspect of the project you should focus on.