public void Set(ulong uu)
{
var hi = NumericsHelpers.GetHi(uu);
if (hi != 0)
{
SetSizeLazy(2);
_bits[0] = (uint)uu;
_bits[1] = hi;
}
else
{
_uSmall = NumericsHelpers.GetLo(uu);
_iuLast = 0;
}
}