Fix several bugs, test behavior and profile (insert 8-32 microseconds, delete 22-37 microseconds)

mods/CORE/mcl_scheduler/init.lua

@@ -0,0 +1,204 @@
+--[[
+
+== Radix/Finger queue class
+
+This is a queue based off the concepts behind finger trees (https://en.wikipedia.org/wiki/Finger_tree),
+the radix sort (https://en.wikipedia.org/wiki/Radix_sort) and funnel sort (https://en.wikipedia.org/wiki/Funnelsort)
+
+This algorithm has O(1) deletion and O(k) insertion (k porportional to the time in the future) and uses log_4(n) tree nodes.
+
+At the top level of the queue, there is a 20-element array of linked lists containing tasks that are scheduled to
+start running in the current second. Removing the next linked list of tasks from this array is an O(1) operation.
+
+The queue then has a one-sided finger tree of 20-element lists that are used to replace the initial queue when the
+second rolls over.
+
+]]
+
+function Class()
+	local cls = {}
+	cls.mt = { __index = cls }
+	function cls:new(...)
+		local inst = setmetatable({}, cls.mt)
+		local construct = inst.construct
+		if construct then inst:construct(...) end
+		return inst
+	end
+	return cls
+end
+
+local inner_queue = Class()
+function inner_queue:construct(level)
+	self.level = level
+	self.items = {}
+	self.unsorted_count = 0
+	self.slots = 4
+
+	-- Precompute slot size
+	local slot_size = 20
+	for i = 2,level do
+		slot_size = slot_size * 4
+	end
+	self.slot_size = slot_size
+end
+function inner_queue:get()
+	local slots = self.slots
+	local slot = 5 - slots
+	local ret = self.items[slot]
+	self.items[slot] = nil
+
+	-- Take a way a slot, then refill if needed
+	slots = slots - 1
+	if slots == 0 then
+		if self.next_level then
+			local next_level_get = self.next_level:get()
+			if next_level_get then
+				self.items = next_level_get.items
+			else
+				self.items = {}
+			end
+			slots = 4
+		end
+	end
+	self.slots = slots
+
+	return ret or self:init_slot_list()
+end
+function inner_queue:add_tasks(tasks, time)
+	local task = tasks
+	local slot_size = self.slot_size
+	local level = self.level
+	local slots = self.slots
+
+	while task do
+		local t = task.time
+		t = t - time
+
+		if t > slot_size * slots then
+			-- Add to list for next level in the finger tree
+			task.time = t
+			local curr_task = task
+			task = task.next
+			curr_task.next = self.first_unsorted
+			local count = self.unsorted_count + 1
+			if count > 20 then
+				if not self.next_level then
+					self.next_level = inner_queue:new(self.level + 1)
+				end
+				self.next_level:add_tasks(curr_task, slot_size * slots)
+				self.first_unsorted = nil
+				self.unsorted_count = 0
+			else
+				self.first_unsorted = curr_task
+				self.unsorted_count = count
+			end
+		else
+			-- Task belongs in a slot on this level
+			local slot = math.floor(t / slot_size) + 1 + ( slots - 4 )
+			t = t % slot_size
+			task.time = t
+			local curr_task = task
+			task = task.next
+
+			local list = self.items[slot] or self:init_slot_list()
+			self.items[slot] = list
+
+			if level == 1 then
+				curr_task.next = list[t]
+				list[t] = curr_task
+			else
+				list:add_tasks(curr_task, (slot - 1) * slot_size)
+			end
+		end
+	end
+end
+function inner_queue:init_slot_list()
+	local level = self.level
+	if level == 1 then
+		return { {}, {}, {}, {} }
+	else
+		local r = {}
+		for i=1,4 do
+			r[i] = inner_queue:new(self.level - 1)
+		end
+	end
+end
+
+local queue = Class()
+function queue:construct()
+	self.items = {}
+	self.unsorted_count = 0
+	self.m_tick = 1
+	self.next_level = inner_queue:new(1)
+end
+function queue:add_task(task)
+	-- Adjust time to align with the start of the current second
+	task.time = task.time + self.m_tick
+
+	-- Handle task in current seccond
+	if task.time <= 20 then
+		task.next = self.items[task.time]
+		self.items[task.time] = task
+		return
+	end
+
+	local count = self.unsorted_count + 1
+	if count > 20 then
+		-- Push to next level
+		self.unsorted_count = 0
+	else
+		-- Add to the list of tasks for later time slots
+		task.next = self.first_unsorted
+		self.first_unsorted = task
+		self.unsorted_count = count
+	end
+end
+function queue:tick()
+	-- Get the tasks for this tick
+	local ret = self.items[self.m_tick]
+	self.items[self.m_tick] = nil
+	self.m_tick = self.m_tick + 1
+
+	-- Handle second rollover
+	if self.m_tick == 21 then
+		-- Push items to next level
+		if self.first_unsorted then
+			self.next_level:add_tasks(self.first_unsorted, 20)
+			self.first_unsorted = nil
+			self.unsorted_count = 0
+		end
+
+		self.items = self.next_level:get()
+		self.m_tick = 1
+	end
+
+	return ret or {}
+end
+
+local t = queue.new()
+
+local test_times = { 15, 1, 7, 34, 50, 150, 14, 18, 20, 20, 15, }
+
+local start_time = minetest.get_us_time()
+for _,time in pairs(test_times) do
+	t:add_task({ time = time })
+
+	local stop_time = minetest.get_us_time()
+	print("took "..tostring(stop_time - start_time).."us")
+	start_time = stop_time
+end
+
+print(dump(t:tick()))
+print(dump(t))
+
+local start_time = minetest.get_us_time()
+for i=1,60 do
+	local s = t:tick()
+	print("time="..tostring(i+1))
+	print(dump(s))
+
+	local stop_time = minetest.get_us_time()
+	print("took "..tostring(stop_time - start_time).."us")
+	start_time = stop_time
+end
+