benchmark.lua

local sum = 0   -- just for benchmark

-- insert elements into some object
local function insert(obj, elem1, elem2, ...)
   -- this function may have 1..inf actual arguments
   if not elem2 and elem1 then
      -- user invoked this function to insert single element
      -- this is the most frequent usage of this function
      -- for the sake of performance we avoid to create a table
      ----------------------------------------------------------------
      -- optimized code for inserting single element (elem1)
      ----------------------------------------------------------------
      sum = sum + elem1  -- this line is just for contrived benchmark
   else  -- "else" branch is not being benchmarked
      -- user invoked this function to insert multiple elements
      -- we are creating a table containing named arguments and varargs
      local elems = {elem1, elem2, ...}
      for j = 1, #elems % 8 do
         insert(obj, elems[j]) -- recursive call to insert one element
      end
      for j = #elems % 8 + 1, #elems, 8 do
         local e1, e2, e3, e4, e5, e6, e7, e8 = unpack(elems, j, j + 7)
         ----------------------------------------------------------------
         -- inserting full block of eight elements
         -- (it is faster than inserting 8 elements one-by-one)
         ----------------------------------------------------------------
      end
   end
end

local time_start = os.clock()
for j = 1, 1e8 do
   insert(nil, 1)
end
print(os.clock() - time_start)