Lua math ライブラリが遅い?
math ライブラリが遅いって聞いたけど
#!lua
# math1.lua
for i = -5000000, 5000000 do
math.abs(i)
end#!lua
# mathrep.lua
function abs(i)
if i < 0 then return -i else return i end
end
for i = -5000000, 5000000 do
abs(i)
end#!lua
# math2.lua
abs = math.abs
for i = -5000000, 5000000 do
abs(i)
end$ repeat 5 time lua -v math1.lua Lua 5.1.1 Copyright (C) 1994-2006 Lua.org, PUC-Rio lua -v math1.lua 2.68s user 0.02s system 99% cpu 2.719 total Lua 5.1.1 Copyright (C) 1994-2006 Lua.org, PUC-Rio lua -v math1.lua 2.68s user 0.01s system 99% cpu 2.710 total Lua 5.1.1 Copyright (C) 1994-2006 Lua.org, PUC-Rio lua -v math1.lua 2.68s user 0.01s system 99% cpu 2.712 total Lua 5.1.1 Copyright (C) 1994-2006 Lua.org, PUC-Rio lua -v math1.lua 2.68s user 0.01s system 99% cpu 2.711 total Lua 5.1.1 Copyright (C) 1994-2006 Lua.org, PUC-Rio lua -v math1.lua 2.68s user 0.01s system 99% cpu 2.711 total
$ repeat 5 time lua -v mathrep.lua Lua 5.1.1 Copyright (C) 1994-2006 Lua.org, PUC-Rio lua -v mathrep.lua 2.51s user 0.02s system 98% cpu 2.562 total Lua 5.1.1 Copyright (C) 1994-2006 Lua.org, PUC-Rio lua -v mathrep.lua 2.52s user 0.02s system 99% cpu 2.548 total Lua 5.1.1 Copyright (C) 1994-2006 Lua.org, PUC-Rio lua -v mathrep.lua 2.51s user 0.01s system 99% cpu 2.545 total Lua 5.1.1 Copyright (C) 1994-2006 Lua.org, PUC-Rio lua -v mathrep.lua 2.52s user 0.01s system 99% cpu 2.547 total Lua 5.1.1 Copyright (C) 1994-2006 Lua.org, PUC-Rio lua -v mathrep.lua 2.51s user 0.01s system 99% cpu 2.547 total
$ repeat 5 time lua -v math2.lua Lua 5.1.1 Copyright (C) 1994-2006 Lua.org, PUC-Rio lua -v math1.lua 2.17s user 0.01s system 99% cpu 2.195 total Lua 5.1.1 Copyright (C) 1994-2006 Lua.org, PUC-Rio lua -v math1.lua 2.17s user 0.01s system 99% cpu 2.192 total Lua 5.1.1 Copyright (C) 1994-2006 Lua.org, PUC-Rio lua -v math1.lua 2.17s user 0.01s system 99% cpu 2.198 total Lua 5.1.1 Copyright (C) 1994-2006 Lua.org, PUC-Rio lua -v math1.lua 2.17s user 0.01s system 99% cpu 2.191 total Lua 5.1.1 Copyright (C) 1994-2006 Lua.org, PUC-Rio lua -v math1.lua 2.17s user 0.01s system 99% cpu 2.193 total
結論：(少なくとも Mac 上の 5.1.1 の math.abs については) テーブルのキーをひくのがおそいだけで、関数自体は math のほうが高速