gistfile1.txt

┌──[poprocks@soter]─[~]
└── $ cat x.lua 
ffi = require("ffi")
ffi.cdef[[
    typedef long time_t;

    typedef struct timeval {
        time_t tv_sec;
        time_t tv_usec;
    } timeval;

    int gettimeofday(struct timeval* t, void* tzp);
]]

gettimeofday_struct = ffi.new("timeval")

local function gettimeofday()
    ffi.C.gettimeofday(gettimeofday_struct, nil)
    return tonumber(gettimeofday_struct.tv_sec) * 1000000 + tonumber(gettimeofday_struct.tv_usec)
end


local v = require "jit.v"
v.on("/dev/stderr")

local ti = table.insert
local ok, tc = pcall(require, "table.clear")

local t = {}
local x = 0

local start

start = gettimeofday()
for i = 1, 10000000 do
    t[#t + 1] = "foo"
end
print(gettimeofday() - start)

tc(t)

start = gettimeofday()
for i = 1, 10000000 do
    ti(t, "foo")
end
print(gettimeofday() - start)

tc(t)

start = gettimeofday()
for i = 1, 10000000 do
    x = x + 1
    t[i] = "foo"
end
print(gettimeofday() - start)
┌──[poprocks@soter]─[~]
└── $ luajit ./x.lua 
[TRACE   1 x.lua:33 loop]
[TRACE   2 (1/2) x.lua:34 -> 1]
1960384
[TRACE   3 x.lua:41 loop]
2091703
[TRACE   4 x.lua:49 loop]
10771