Power of Two function benchmark for luajit (löve used for timing)

pot_bench.lua

local potLut = {}
potLut[0] = 1
for i = 1, 32 do
    potLut[i] = potLut[i-1] * 2
end

-- compare this with lshift(2, n)
local function potA(n) -- power of two
    return potLut[n]
end

local bit = require("bit")
local lshift = bit.lshift

local function potB(n)
    return math.abs(lshift(1, n)) -- because lshift(1, 31) = -2147483648
end

local function potBf(n)
    return lshift(1, n)
end

local function potC(n)
    return 2^n
end

-------------------------------------

local values = {}
for i = 1, 40000000 do
    local n = love.math.random(0, 31)
    assert(potA(n) == potB(n) and potA(n) == potC(n)) -- potBf is wrong anyways
    values[#values + 1] = n
end


local start = love.timer.getTime()
for i = 1, #values do
    local res = potA(values[i])
end
print("LUT func: " .. (love.timer.getTime() - start))


local start = love.timer.getTime()
for i = 1, #values do
    local res = potLut[values[i]]
end
print("LUT lookup: " .. (love.timer.getTime() - start))


local start = love.timer.getTime()
for i = 1, #values do
    local res = potB(values[i])
end
print("bit.lshift: " .. (love.timer.getTime() - start))

local start = love.timer.getTime()
for i = 1, #values do
    local res = potBf(values[i])
end
print("bit.lshift without abs: " .. (love.timer.getTime() - start))

local start = love.timer.getTime()
for i = 1, #values do
    local res = potC(values[i])
end
print("pow: " .. (love.timer.getTime() - start))

results.txt

LUT func:               0.066940495627932
LUT lookup:             0.067318620625883
bit.lshift:             0.027310643810779
bit.lshift without abs: 0.029313809820451 (I don't know why it's slower, but this behaviour persists between runs)
pow:                    0.059891540324315