Experimental ABM Multiplexing

Detect ABMs that share the same "signature"
except for the central nodenames, and use a
single ABM to run them, looking up the core
bodies to run based on nodename on the Lua
side.  This could reduce the total number of
ABMs we're using by almost half, and
mitigate some of the performance issues
that MT continues to have with ABMs.

mods/nc_api_active/abmmux.lua

@@ -0,0 +1,83 @@
+-- LUALOCALS < ---------------------------------------------------------
+local minetest, nodecore, pairs, rawset, table
+    = minetest, nodecore, pairs, rawset, table
+local table_concat
+    = table.concat
+-- LUALOCALS > ---------------------------------------------------------
+
+local muxdefs = {}
+local abmsdefined = {}
+
+local grp = "group:"
+local function matches(name, def, nodenames)
+	for _, n in pairs(nodenames) do
+		if name == n then return true
+		elseif n:sub(1, #grp) == grp and def.groups and def.groups[n:sub(#n + 1)] then
+			return true
+		end
+	end
+end
+
+nodecore.register_on_register_item(function(name, def)
+		if def.type == "node" then
+			for _, mux in pairs(muxdefs) do
+				if matches(name, def, mux.nodenames) then
+					rawset(def.groups, "abmmux_" .. mux.muxkey, 1)
+				end
+			end
+		end
+	end)
+
+local muxidx = nodecore.item_matching_index(muxdefs,
+	function(i) return i.nodenames end,
+	"register_abm",
+	true,
+	function(n, i) return i.muxkey .. n end
+)
+
+local oldreg = minetest.register_abm
+function minetest.register_abm(def)
+	local rawkey = table_concat({
+			def.interval,
+			def.chance,
+			def.catchup and 1 or 0,
+			table_concat(def.neighbors or {}, ";")
+		}, "|")
+	local muxkey = minetest.sha1(rawkey):sub(1, 8)
+	def.muxkey = muxkey
+	muxdefs[#muxdefs + 1] = def
+	for k, v in pairs(minetest.registered_nodes) do
+		if matches(k, v, def.nodenames) then
+			rawset(v.groups, "abmmux_" .. muxkey, 1)
+			minetest.override_item(k, {groups = v.groups})
+		end
+	end
+	if abmsdefined[muxkey] then return end
+	abmsdefined[muxkey] = true
+	local abmaction
+	abmaction = function(pos, node, ...)
+		local oldname = node.name
+		local found = muxidx[muxkey .. oldname]
+		if not found then
+			abmaction = function() end
+			return
+		end
+		if #found == 1 then
+			abmaction = found[1].action
+			return found[1].action(pos, node, ...)
+		end
+		for _, d in pairs(found) do
+			d.action(pos, node, ...)
+			if minetest.get_node(pos).name ~= oldname then return end
+		end
+	end
+	return oldreg({
+			label = "mux abm for " .. rawkey,
+			interval = def.interval,
+			chance = def.chance,
+			catchup = def.catchup,
+			neighbors = def.neighbors,
+			nodenames = {"group:abmmux_" .. muxkey},
+			action = function(...) return abmaction(...) end
+		})
+end

mods/nc_api_active/init.lua

@@ -5,6 +5,7 @@ local include, nodecore
 
 nodecore.amcoremod()
 
+include("abmmux")
 include("stasis")
 include("abmhack")
 include("dnts")