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91 lines
2.2 KiB
Lua
91 lines
2.2 KiB
Lua
-- Pseudo random number generation module for Lunatic
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local ffi = require("ffi")
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local ffiC = ffi.C
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local rawset = rawset
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local type = type
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local decl = decl -- comes from above (_defs_game.lua)
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local print = print -- for commented out debug block in new() below
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module(...)
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-- PRNG state struct
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ffi.cdef[[
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typedef struct {
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uint32_t x, y, z, c;
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} rng_jkiss_t;
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typedef union { unsigned char u[16]; double d[2]; } uchar_double_u_t;
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]]
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-- PRNG functions
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decl[[
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uint32_t rand_jkiss_u32(rng_jkiss_t *s);
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double rand_jkiss_dbl(rng_jkiss_t *s);
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uint32_t Bcrc32(const void* data, size_t length, uint32_t crc);
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]]
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local function get_rand_u32(tin)
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tin.d[0] = ffiC.gethiticks() % 1
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tin.d[1] = ffiC.gethiticks() % 1
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return ffiC.Bcrc32(tin.u, 16, 0)
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end
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local mt = {
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__tostring = function(s)
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return "rand.new("..s.x..","..s.y..","..s.z..","..s.c..")"
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end,
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__index = {
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getu32 = ffiC.rand_jkiss_u32,
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getdbl = ffiC.rand_jkiss_dbl,
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-- Initialize the JKISS PRNG using the CRC32 of the result of several
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-- profiling timer calls interpreted as byte sequence.
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init_time_md4 = function(s)
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local tin = ffi.new("uchar_double_u_t")
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local tout = ffi.new("uint32_t [4]")
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repeat
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s.y = get_rand_u32(tin)
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until (s.y ~= 0) -- y must not be zero!
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s.x = get_rand_u32(tin)
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s.z = get_rand_u32(tin)
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s.c = get_rand_u32(tin) % 698769068 + 1 -- Should be less than 698769069
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end,
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},
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}
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local jkiss = ffi.metatype("rng_jkiss_t", mt)
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function new(x,y,z,c)
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local s
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if (x == nil or type(x)=="boolean") then
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-- initialize with arbitrary but fixed state
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s = jkiss(123456789, 987654321, 43219876, 6543217)
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if (x) then
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s:init_time_md4()
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end
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else
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s = jkiss(x,y,z,c)
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end
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--[[
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local r=ffi.new("rng_jkiss_t")
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r.x = 123456789; r.y = 987654321; r.z = 43219876; r.c = 6543217;
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local N = 1e7
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local t=ffiC.gethiticks()
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for i=1,N do
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ffiC.rand_jkiss_dbl(r)
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end
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print("RANDGEN TIME: "..ffiC.gethiticks()-t) -- x86_64: approx. 100 ms
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--]]
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return s
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end
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