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115 lines
2.2 KiB
Lua
Executable file
115 lines
2.2 KiB
Lua
Executable file
#!/usr/bin/env luajit
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local ffi = require "ffi"
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local io = require "io"
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local os = require "os"
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local math = require "math"
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local tablesfn = arg[1]
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local taylor_n = tonumber(arg[2])
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if (tablesfn==nil) then
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-- taylor_n is a number: use that n for Taylor approximation of atan
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-- taylor_n==nil: use math.atan
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print("Usage: ./tables.lua ../path/to/TABLES.DAT [talyor_n]")
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return 1
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end
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local fd, errmsg = io.open(tablesfn)
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if (fd==nil) then
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print("Failed opening "..tablesfn..": "..errmsg)
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return 1 -- XXX: not working, neither os.exit(1) as of 20120901
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end
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local sintab = ffi.new("int16_t [?]", 2048)
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local sinstr = fd:read(2048*2)
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if (sinstr==nil or #sinstr<2048*2) then
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print("Failed reading whole sine table")
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fd:close()
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return 1
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end
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ffi.copy(sintab, sinstr, 2048*2)
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sinstr = nil
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--== sintable
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local oursin = ffi.new("int16_t [?]", 2048)
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local BANG2RAD = math.pi/1024
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for a=0,2047 do
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local s = 16384*math.sin(a*BANG2RAD)
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oursin[a] = s
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-- if (a < 1024) then print(a..": "..s) end
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end
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--print("")
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for a=0,2047 do
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local dif = oursin[a]-sintab[a]
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assert(dif == 0)
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--[[
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if (dif ~= 0) then
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print(a..": "..dif)
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end
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--]]
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if (a < 512) then
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assert(sintab[a] == sintab[1024-a])
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end
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if (a >= 1024) then
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assert(sintab[a] == -sintab[a-1024])
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end
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end
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--== radarang
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local ratab = ffi.new("int16_t [?]", 640)
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local rastr = fd:read(640*2)
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fd:close()
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ffi.copy(ratab, rastr, 640*2)
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rastr = nil
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local function atan_taylor(x, n)
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local absx = math.abs(x)
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local at = 0
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for i=0,n do
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local twoip2 = 2*i+1
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local xp = x^twoip2
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local pmone = (-1)^i
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if (absx < 1) then
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at = at + (pmone * xp)/twoip2
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else
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at = at + pmone/(xp * twoip2)
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end
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end
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if (absx > 1) then
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at = math.pi/2 - at
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end
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return at
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end
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local atan
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if (taylor_n==nil) then
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atan = math.atan
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else
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atan = function (x) return atan_taylor(x, taylor_n) end
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end
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for i=0,639 do
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local at = -64*atan((640-0.5-i)/160)/BANG2RAD
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local ra = ratab[i]
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at = math.ceil(at)
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-- print(i ..": ".. ra .." ".. at .." ".. at/ra .." ".. at-ra)
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end
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--[[
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local ourra = ffi.new("int16_t [?]", 640)
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--]]
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