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Roblox
GitHub Repository: Roblox/luau
 Path: blob/master/bench/tests/shootout/fannkuch-redux.lua
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--[[

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MIT License

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Copyright (c) 2017 Gabriel de Quadros Ligneul

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Permission is hereby granted, free of charge, to any person obtaining a copy

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of this software and associated documentation files (the "Software"), to deal

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in the Software without restriction, including without limitation the rights

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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

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copies of the Software, and to permit persons to whom the Software is

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furnished to do so, subject to the following conditions:

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The above copyright notice and this permission notice shall be included in all

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copies or substantial portions of the Software.

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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE

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SOFTWARE.

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]]

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-- The Computer Language Benchmarks Game

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-- http://benchmarksgame.alioth.debian.org/

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-- contributed by Mike Pall

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local function prequire(name) local success, result = pcall(require, name); return success and result end

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local bench = script and require(script.Parent.bench_support) or prequire("bench_support") or require("../../bench_support")

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function test()

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local function fannkuch(n)

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  local p, q, s, sign, maxflips, sum = {}, {}, {}, 1, 0, 0

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  for i=1,n do p[i] = i; q[i] = i; s[i] = i end

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  repeat

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    -- Copy and flip.

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    local q1 = p[1]				-- Cache 1st element.

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    if q1 ~= 1 then

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      for i=2,n do q[i] = p[i] end		-- Work on a copy.

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      local flips = 1

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      repeat

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	local qq = q[q1]

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	if qq == 1 then				-- ... until 1st element is 1.

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	  sum = sum + sign*flips

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	  if flips > maxflips then maxflips = flips end -- New maximum?

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	  break

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	end

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	q[q1] = q1

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	if q1 >= 4 then

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	  local i, j = 2, q1 - 1

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	  repeat q[i], q[j] = q[j], q[i]; i = i + 1; j = j - 1; until i >= j

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	end

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	q1 = qq; flips = flips + 1

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      until false

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    end

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    if sign == 1 then

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      p[2], p[1] = p[1], p[2]; sign = -1	-- Rotate 1<-2.

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    else

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      p[2], p[3] = p[3], p[2]; sign = 1		-- Rotate 1<-2 and 1<-2<-3.

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      for i=3,n do

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	local sx = s[i]

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	if sx ~= 1 then s[i] = sx-1; break end

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	if i == n then return sum, maxflips end	-- Out of permutations.

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	s[i] = i

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	-- Rotate 1<-...<-i+1.

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	local t = p[1]; for j=1,i do p[j] = p[j+1] end; p[i+1] = t

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      end

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    end

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  until false

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end

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local n = tonumber(arg and arg[1]) or 8

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local sum, flips = fannkuch(n)

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print(sum, "\nPfannkuchen(", n, ") = ", flips, "\n")

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end

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bench.runCode(test, "fannkuchen-redux")

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