GPU path tracer with adaptive antialiasing

Adaptive antialiasing is algorithm which minimize samples per pixel and serve to remove variance faster. Pixels with big variance get more samples and variance is gone faster then when we use uniform sampling. Algorithm is not complicated. I compare difference between new sample and previous samples and if variance is bigger then threshold, I create new sample, then I compare with bigger variance and sample more and more for small variance to big. Last 2 examples without adaptive antialiasing for comparing