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 hashes = {
	h129	= function(h, x) return (h << 5) + (h >> 2) + x end,
	h129_43	= function(h, x) return (h << 4) + (h >> 3) + x end,
	h127	= function(h, x) return (h << 4) - (h >> 3) + x end,
	h127_52	= function(h, x) return (h << 5) - (h >> 2) + x end,
	aaab	= function(h, x) return ((h + x) * 0xAAAB) >> 3 end
}

local function genhexs(n)
	local random = math.random
	local words = {}
	for i = 1, n do
		local tmp = {}
		for j = 1, 8 do
			tmp[j] = string.format('%04x', random(0, 65535))
		end
		words[i] = table.concat(tmp)
	end
	return words
end

local function readwords(filename)
	local words = {}
	local n = 1
	for line in io.lines(filename) do
		words[n] = line
		n = n + 1
	end
	return words
end
local function shuffle(words)
	local n = #words
	for i = 1, n - 1 do
		local j = math.random(i, n)
		words[i], words[j] = words[j], words[i]
	end
	return words
end

local words = shuffle(readwords('words_alpha.txt'))
--local words = genhexs(100000)
print(#words, 'words')

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

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

local N = 22
local tmp = {}
local results = {}
for hashname in pairs(hashes) do
	results[hashname] = {}
end
for i = 3, N, 2 do
	local slots = i
	table.insert(tmp, string.format('\t%d/%d', slots, 1 << slots))
	local ranks = {}
	for hashname, hashfunc in pairs(hashes) do
		table.insert(ranks, { hashname = hashname, collisions = test(words, slots, hashfunc) })
	end
	table.sort(ranks, function(a, b) return a.collisions < b.collisions end)
	for i, rank in ipairs(ranks) do
		results[rank.hashname][i] = { collisions = rank.collisions, rank = i }
	end
end
print(table.concat(tmp))
for hashname in pairs(hashes) do
	tmp = { hashname }
	for i = 3, N, 2 do
		local result = results[hashname][i]
		table.insert(tmp, string.format('\t(%d)%d', result.rank, result.collisions))
	end
	print(table.concat(tmp))
end