const size_t currentSeed = unpredictableSeed(); static if(vdebug){write("UT: hSR. "); writeln("seed: ", currentSeed);} rndGenInUse.seed(currentSeed); //initialize the random generator const size_t M = uniform(1U,size_t.max/2, rndGenInUse); //set universe size to some integer. auto hSR = hSR(M); assert((hSR & (hSR - 1)) == 0); if(hSR < uint.max) assert(hSR >= sqrt(to!float(M))); const auto check = powersOfTwo.until(hSR).array; assert((check[$-1]) * (check[$-1]) < M);
This function returns the higher square root of the given input. It is needed in the initialization step of the VEB tree to calculate the number of children of a given layer. And this is the universe size of the summary of a node. The upper square root is defined by 2^{\lceil(\lg u)/2\rceil}