Compare some hash function for lua table implementation

hashcompare.lua

--[[
370104 words from https://github.com/dwyl/english-words/blob/master/words_alpha.txt

                             3/4             5/8             7/8             9/16            11/16           13/16           15/32           17/32           19/32           21/32
(h<<5) + (h>>2) + x       (3)84874        (4)81670        (4)113326       (4)80336        (2)96169        (5)111520       (4)125243       (3)79309        (4)87762        (5)95643
(h<<4) + (h>>3) + x       (2)84819        (1)81351        (3)113283       (5)80439        (3)96264        (2)111197       (3)125200       (4)79486        (2)87582        (2)95430
(h<<5) - (h>>2) + x       (1)84464        (2)81428        (2)113108       (2)80201        (4)96464        (4)111469       (1)125052       (2)79222        (3)87666        (3)95466
(h<<4) - (h>>3) + x       (4)85050        (3)81587        (1)113084       (1)80112        (1)96131        (1)111134       (2)125185       (1)79163        (1)87361        (1)95239
((h + x) * 0xAAAB) >> 3   (5)85143        (5)81973        (5)113538       (3)80323        (5)96593        (3)111401       (5)125306       (5)79636        (5)88120        (4)95536

]]

local seed = 0
local dictfile = "words_alpha.txt"

local hash = {}

function hash.h129(h, x)
	return (h<<5) + (h>>2) + x
end

function hash.h129_43(h,x)
	return (h<<4) + (h>>3) + x
end

function hash.h127(h, x)
	return (h<<4) - (h>>3) + x
end

function hash.h127_52(h, x)
	return (h<<5) - (h>>2) + x
end

function hash.aaab(h, x)
	return ((h + x) * 0xAAAB) >> 3
end

local function shuffle(t)
	local n = #t
	for i = 1, n-1 do
		local idx = math.random(i, n)
		t[i], t[idx] = t[idx], t[i]
	end
	return t
end

local function readdict(filename)
	local dict = {}
	local n = 1
	for line in io.lines(filename) do
		dict[n] = line
		n = n + 1
	end
	return dict
end

local function hashstring(str, func)
	local h = seed ~ #str
	str:gsub(".", function (c)
		h = h ~ ( func(h, c:byte()) & 0xffffffff )
		return ""	-- this make gsub faster
	end)
	return h
end

local function test(dict, slots, hashfunc)
	local size = 1 << slots
	local colliding = 0
	for i = 1, #dict-slots+1, slots do
		local tbl = {}
		for j = 0, slots-1 do
			local h = hashstring(dict[i+j], hashfunc) % size
			if tbl[h] then
				colliding = colliding + 1
			else
				tbl[h] = true
			end
		end
	end
	return colliding
end

local function genguid(n)
	local random = math.random
	local dict = {}
	for i = 1, n do
		local tmp = {}
		for j = 1, 16 do
			tmp[j] = string.format("%02x", random(0,255))
		end
		dict[i] = table.concat(tmp)
	end
	return dict
end

local dict = shuffle(readdict(dictfile))
-- local dict = genguid(100000)

print(#dict, "words")

local results = {}

for key in pairs(hash) do
	results[key] = {}
end

local N = 22

for i = 3, N, 2 do
	local group = i
	print(string.format("%d/%d", group, 1<<group))
	local rank = {}
	for key, func in pairs(hash) do
		local c = test(dict, group, func)
		table.insert(rank, { c = c , key = key })
	end
	table.sort(rank, function(a,b) return a.c < b.c end)
	for r, obj in ipairs(rank) do
		results[obj.key][i] = { c = obj.c , rank = r }
	end
end

for key in pairs(hash) do
	local tmp = {}
	for i = 3, N, 2 do
		local obj = results[key][i]
		table.insert(tmp, string.format("(%d)%d", obj.rank, obj.c))
	end
	print(key, table.concat(tmp, "\t"))
end