benchmark: https://gist.github.com/ofseed/6224529d77c016c36f7ab2f977059848
local rounds = tonumber(arg[1]) or 1000
local count = tonumber(arg[2]) or 1000
-- Load the table.clear function.
local clear = require("table.clear")
local function fill(t, n)
for i = 1, n do
t[i] = i
end
end
local function bench_reassign(n_rounds, n_items)
local t = {}
local start = os.clock()
for _ = 1, n_rounds do
t = {}
collectgarbage("collect")
fill(t, n_items)
end
return os.clock() - start
end
local function bench_reassign_no_gc(n_rounds, n_items)
local t = {}
local start = os.clock()
for _ = 1, n_rounds do
t = {}
fill(t, n_items)
end
return os.clock() - start
end
local function bench_clear(n_rounds, n_items)
local t = {}
local start = os.clock()
for _ = 1, n_rounds do
clear(t)
fill(t, n_items)
end
return os.clock() - start
end
-- Warm up LuaJIT before the real benchmark.
do
local t = {}
for _ = 1, 2000 do
clear(t)
fill(t, count)
end
end
collectgarbage("collect")
local reassign_time = bench_reassign(rounds, count)
collectgarbage("collect")
local reassign_no_gc_time = bench_reassign_no_gc(rounds, count)
collectgarbage("collect")
local clear_time = bench_clear(rounds, count)
print(string.format("rounds=%d count=%d", rounds, count))
print(string.format("t = {} + GC : %.6f s", reassign_time))
print(string.format("t = {} : %.6f s", reassign_no_gc_time))
print(string.format("table.clear : %.6f s", clear_time))
print(string.format("vs + GC : %.2fx", reassign_time / clear_time))
print(string.format("vs no GC : %.2fx", reassign_no_gc_time / clear_time))
benchmark result:
rounds=1000 count=1000
t = {} + GC : 0.022469 s
t = {} : 0.002570 s
table.clear : 0.000387 s
vs + GC : 58.06x
vs no GC : 6.64x
`count` is how many items the table has, and `round` is how many rounds we fill
the table, clear, and then refill it. `table = {}` is clear the table by
resigning a new empty one, because this script does not run persistently like
nvim so GC is not triggered, so I added another extreme control group that
manually triggers GC.
Yi Ming