Add support for the PCG32 PRNG algo (and associated script APIs)

doc/lua_api.txt

@@ -2515,7 +2515,8 @@ an itemstring, a table or `nil`.
   Returns taken `ItemStack`.
 
 ### `PseudoRandom`
-A pseudorandom number generator.
+A 16-bit pseudorandom number generator.
+Uses a well-known LCG algorithm introduced by K&R.
 
 It can be created via `PseudoRandom(seed)`.
 
@@ -2525,6 +2526,19 @@ It can be created via `PseudoRandom(seed)`.
     * `((max - min) == 32767) or ((max-min) <= 6553))` must be true
       due to the simple implementation making bad distribution otherwise.
 
+### `PcgRandom`
+A 32-bit pseudorandom number generator.
+Uses PCG32, an algorithm of the permuted congruential generator family, offering very strong randomness.
+
+It can be created via `PcgRandom(seed)` or `PcgRandom(seed, sequence)`.
+
+#### Methods
+* `next()`: return next integer random number [`-2147483648`...`2147483647`]
+* `next(min, max)`: return next integer random number [`min`...`max`]
+* `rand_normal_dist(min, max, num_trials=6)`: return normally distributed random number [`min`...`max`]
+    * This is only a rough approximation of a normal distribution with mean=(max-min)/2 and variance=1
+    * Increasing num_trials improves accuracy of the approximation
+
 ### `PerlinNoise`
 A perlin noise generator.
 It can be created via `PerlinNoise(seed, octaves, persistence, scale)`

src/mapgen.cpp

@@ -515,14 +515,10 @@ void MapgenParams::load(const Settings &settings)
 	std::string seed_str;
 	const char *seed_name = (&settings == g_settings) ? "fixed_map_seed" : "seed";
 
-	if (settings.getNoEx(seed_name, seed_str) && !seed_str.empty()) {
+	if (settings.getNoEx(seed_name, seed_str) && !seed_str.empty())
 		seed = read_seed(seed_str.c_str());
-	} else {
-		seed = ((u64)(myrand() & 0xFFFF) << 0) |
-			((u64)(myrand() & 0xFFFF) << 16) |
-			((u64)(myrand() & 0xFFFF) << 32) |
-			((u64)(myrand() & 0xFFFF) << 48);
-	}
+	else
+		myrand_bytes(&seed, sizeof(seed));
 
 	settings.getNoEx("mg_name", mg_name);
 	settings.getS16NoEx("water_level", water_level);

src/mg_ore.cpp

@@ -308,7 +308,7 @@ void OreVein::generate(MMVManip *vm, int mapseed, u32 blockseed,
 		}
 
 		// randval ranges from -1..1
-		float randval   = (float)pr.next() / (PSEUDORANDOM_MAX / 2) - 1.f;
+		float randval   = (float)pr.next() / (pr.RANDOM_RANGE / 2) - 1.f;
 		float noiseval  = contour(noise->result[index]);
 		float noiseval2 = contour(noise2->result[index]);
 		if (noiseval * noiseval2 + randval * random_factor < nthresh)

src/noise.cpp

@@ -62,6 +62,107 @@ FlagDesc flagdesc_noiseparams[] = {
 
 ///////////////////////////////////////////////////////////////////////////////
 
+PcgRandom::PcgRandom(u64 state, u64 seq)
+{
+	seed(state, seq);
+}
+
+void PcgRandom::seed(u64 state, u64 seq)
+{
+	m_state = 0U;
+	m_inc = (seq << 1u) | 1u;
+	next();
+	m_state += state;
+	next();
+}
+
+
+u32 PcgRandom::next()
+{
+	u64 oldstate = m_state;
+	m_state = oldstate * 6364136223846793005ULL + m_inc;
+
+	u32 xorshifted = ((oldstate >> 18u) ^ oldstate) >> 27u;
+	u32 rot = oldstate >> 59u;
+	return (xorshifted >> rot) | (xorshifted << ((-rot) & 31));
+}
+
+
+u32 PcgRandom::range(u32 bound)
+{
+	/*
+	If the bound is not a multiple of the RNG's range, it may cause bias,
+	e.g. a RNG has a range from 0 to 3 and we take want a number 0 to 2.
+	Using rand() % 3, the number 0 would be twice as likely to appear.
+	With a very large RNG range, the effect becomes less prevalent but
+	still present.  This can be solved by modifying the range of the RNG
+	to become a multiple of bound by dropping values above the a threshhold.
+	In our example, threshhold == 4 - 3 = 1 % 3 == 1, so reject 0, thus
+	making the range 3 with no bias.
+
+	This loop looks dangerous, but will always terminate due to the
+	RNG's property of uniformity.
+	*/
+	u32 threshhold = -bound % bound;
+	u32 r;
+
+	while ((r = next()) < threshhold);
+
+	return r % bound;
+}
+
+
+s32 PcgRandom::range(s32 min, s32 max)
+{
+	assert(max >= min);
+	u32 bound = max - min + 1;
+	return range(bound) + min;
+}
+
+
+void PcgRandom::bytes(void *out, size_t len)
+{
+	u32 r;
+	u8 *outb = (u8 *)out;
+
+	size_t len_alignment = (uintptr_t)out % sizeof(u32);
+	if (len_alignment) {
+		r = next();
+		while (len_alignment--) {
+			*outb = r & 0xFF;
+			outb++;
+			r >>= 8;
+		}
+	}
+
+	size_t len_dwords = len / sizeof(u32);
+	while (len_dwords--) {
+		r = next();
+		*(u32 *)outb = next();
+		outb += sizeof(u32);
+	}
+
+	size_t len_remaining = len % sizeof(u32);
+	if (len_remaining) {
+		r = next();
+		while (len_remaining--) {
+			*outb = r & 0xFF;
+			outb++;
+			r >>= 8;
+		}
+	}
+}
+
+
+s32 PcgRandom::randNormalDist(s32 min, s32 max, int num_trials)
+{
+	u32 accum = 0;
+	for (int i = 0; i != num_trials; i++)
+		accum += range(min, max);
+	return ((float)accum / num_trials) + 0.5f;
+}
+
+///////////////////////////////////////////////////////////////////////////////
 
 float noise2d(int x, int y, int seed)
 {

src/noise.h

@@ -30,47 +30,67 @@
 #include "irr_v3d.h"
 #include "util/string.h"
 
-#define PSEUDORANDOM_MAX 32767
-
 extern FlagDesc flagdesc_noiseparams[];
 
-class PseudoRandom
-{
+// Note: this class is not polymorphic so that its high level of
+// optimizability may be preserved in the common use case
+class PseudoRandom {
 public:
-	PseudoRandom(): m_next(0)
+	const static u32 RANDOM_RANGE = 32767;
+
+	inline PseudoRandom(int seed=0):
+		m_next(seed)
 	{
 	}
-	PseudoRandom(int seed): m_next(seed)
-	{
-	}
-	void seed(int seed)
+
+	inline void seed(int seed)
 	{
 		m_next = seed;
 	}
-	// Returns 0...PSEUDORANDOM_MAX
-	int next()
+
+	inline int next()
 	{
 		m_next = m_next * 1103515245 + 12345;
-		return((unsigned)(m_next/65536) % (PSEUDORANDOM_MAX + 1));
+		return (unsigned)(m_next / 65536) % (RANDOM_RANGE + 1);
 	}
-	int range(int min, int max)
+
+	inline int range(int min, int max)
 	{
-		if (max-min > (PSEUDORANDOM_MAX + 1) / 10)
-		{
-			//dstream<<"WARNING: PseudoRandom::range: max > 32767"<<std::endl;
-			assert("Something wrong with random number" == NULL);
-		}
-		if(min > max)
-		{
-			assert("Something wrong with random number" == NULL);
-			//return max;
-		}
-		return (next()%(max-min+1))+min;
+		assert(max >= min);
+		/*
+		Here, we ensure the range is not too large relative to RANDOM_MAX,
+		as otherwise the effects of bias would become noticable.  Unlike
+		PcgRandom, we cannot modify this RNG's range as it would change the
+		output of this RNG for reverse compatibility.
+		*/
+		assert((u32)(max - min) <= (RANDOM_RANGE + 1) / 10);
+
+		return (next() % (max - min + 1)) + min;
 	}
+
 private:
 	int m_next;
 };
 
+class PcgRandom {
+public:
+	const static s32 RANDOM_MIN   = -0x7fffffff - 1;
+	const static s32 RANDOM_MAX   = 0x7fffffff;
+	const static u32 RANDOM_RANGE = 0xffffffff;
+
+	PcgRandom(u64 state=0x853c49e6748fea9bULL, u64 seq=0xda3e39cb94b95bdbULL);
+	void seed(u64 state, u64 seq=0xda3e39cb94b95bdbULL);
+	u32 next();
+	u32 range(u32 bound);
+	s32 range(s32 min, s32 max);
+	void bytes(void *out, size_t len);
+	s32 randNormalDist(s32 min, s32 max, int num_trials=6);
+
+private:
+	u64 m_state;
+	u64 m_inc;
+};
+
 #define NOISE_FLAG_DEFAULTS    0x01
 #define NOISE_FLAG_EASED       0x02
 #define NOISE_FLAG_ABSVALUE    0x04
@@ -89,7 +109,8 @@ struct NoiseParams {
 	float lacunarity;
 	u32 flags;
 
-	NoiseParams() {
+	NoiseParams()
+	{
 		offset     = 0.0f;
 		scale      = 1.0f;
 		spread     = v3f(250, 250, 250);

src/script/lua_api/l_noise.cpp

@@ -23,12 +23,19 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "common/c_content.h"
 #include "log.h"
 
-// garbage collector
-int LuaPerlinNoise::gc_object(lua_State *L)
+///////////////////////////////////////
+/*
+  LuaPerlinNoise
+*/
+
+LuaPerlinNoise::LuaPerlinNoise(NoiseParams *params) :
+	np(*params)
+{
+}
+
+
+LuaPerlinNoise::~LuaPerlinNoise()
 {
-	LuaPerlinNoise *o = *(LuaPerlinNoise **)(lua_touserdata(L, 1));
-	delete o;
-	return 0;
 }
 
 
@@ -54,19 +61,6 @@ int LuaPerlinNoise::l_get3d(lua_State *L)
 }
 
 
-LuaPerlinNoise::LuaPerlinNoise(NoiseParams *params) :
-	np(*params)
-{
-}
-
-
-LuaPerlinNoise::~LuaPerlinNoise()
-{
-}
-
-
-// LuaPerlinNoise(seed, octaves, persistence, scale)
-// Creates an LuaPerlinNoise and leaves it on top of stack
 int LuaPerlinNoise::create_object(lua_State *L)
 {
 	NO_MAP_LOCK_REQUIRED;
@@ -91,14 +85,22 @@ int LuaPerlinNoise::create_object(lua_State *L)
 }
 
 
-LuaPerlinNoise* LuaPerlinNoise::checkobject(lua_State *L, int narg)
+int LuaPerlinNoise::gc_object(lua_State *L)
+{
+	LuaPerlinNoise *o = *(LuaPerlinNoise **)(lua_touserdata(L, 1));
+	delete o;
+	return 0;
+}
+
+
+LuaPerlinNoise *LuaPerlinNoise::checkobject(lua_State *L, int narg)
 {
 	NO_MAP_LOCK_REQUIRED;
 	luaL_checktype(L, narg, LUA_TUSERDATA);
 	void *ud = luaL_checkudata(L, narg, className);
 	if (!ud)
 		luaL_typerror(L, narg, className);
-	return *(LuaPerlinNoise**)ud;  // unbox pointer
+	return *(LuaPerlinNoise **)ud;
 }
 
 
@@ -111,7 +113,7 @@ void LuaPerlinNoise::Register(lua_State *L)
 
 	lua_pushliteral(L, "__metatable");
 	lua_pushvalue(L, methodtable);
-	lua_settable(L, metatable);  // hide metatable from Lua getmetatable()
+	lua_settable(L, metatable);
 
 	lua_pushliteral(L, "__index");
 	lua_pushvalue(L, methodtable);
@@ -121,12 +123,11 @@ void LuaPerlinNoise::Register(lua_State *L)
 	lua_pushcfunction(L, gc_object);
 	lua_settable(L, metatable);
 
-	lua_pop(L, 1);  // drop metatable
+	lua_pop(L, 1);
 
-	luaL_openlib(L, 0, methods, 0);  // fill methodtable
-	lua_pop(L, 1);  // drop methodtable
+	luaL_openlib(L, 0, methods, 0);
+	lua_pop(L, 1);
 
-	// Can be created from Lua (PerlinNoise(seed, octaves, persistence)
 	lua_register(L, className, create_object);
 }
 
@@ -138,16 +139,26 @@ const luaL_reg LuaPerlinNoise::methods[] = {
 	{0,0}
 };
 
-
+///////////////////////////////////////
 /*
-  PerlinNoiseMap
- */
+  LuaPerlinNoiseMap
+*/
 
-int LuaPerlinNoiseMap::gc_object(lua_State *L)
+LuaPerlinNoiseMap::LuaPerlinNoiseMap(NoiseParams *params, int seed, v3s16 size)
 {
-	LuaPerlinNoiseMap *o = *(LuaPerlinNoiseMap **)(lua_touserdata(L, 1));
-	delete o;
-	return 0;
+	m_is3d = size.Z > 1;
+	np = *params;
+	try {
+		noise = new Noise(&np, seed, size.X, size.Y, size.Z);
+	} catch (InvalidNoiseParamsException &e) {
+		throw LuaError(e.what());
+	}
+}
+
+
+LuaPerlinNoiseMap::~LuaPerlinNoiseMap()
+{
+	delete noise;
 }
 
 
@@ -251,26 +262,6 @@ int LuaPerlinNoiseMap::l_get3dMap_flat(lua_State *L)
 }
 
 
-LuaPerlinNoiseMap::LuaPerlinNoiseMap(NoiseParams *params, int seed, v3s16 size)
-{
-	m_is3d = size.Z > 1;
-	np = *params;
-	try {
-		noise = new Noise(&np, seed, size.X, size.Y, size.Z);
-	} catch (InvalidNoiseParamsException &e) {
-		throw LuaError(e.what());
-	}
-}
-
-
-LuaPerlinNoiseMap::~LuaPerlinNoiseMap()
-{
-	delete noise;
-}
-
-
-// LuaPerlinNoiseMap(np, size)
-// Creates an LuaPerlinNoiseMap and leaves it on top of stack
 int LuaPerlinNoiseMap::create_object(lua_State *L)
 {
 	NoiseParams np;
@@ -286,6 +277,14 @@ int LuaPerlinNoiseMap::create_object(lua_State *L)
 }
 
 
+int LuaPerlinNoiseMap::gc_object(lua_State *L)
+{
+	LuaPerlinNoiseMap *o = *(LuaPerlinNoiseMap **)(lua_touserdata(L, 1));
+	delete o;
+	return 0;
+}
+
+
 LuaPerlinNoiseMap *LuaPerlinNoiseMap::checkobject(lua_State *L, int narg)
 {
 	luaL_checktype(L, narg, LUA_TUSERDATA);
@@ -294,7 +293,7 @@ LuaPerlinNoiseMap *LuaPerlinNoiseMap::checkobject(lua_State *L, int narg)
 	if (!ud)
 		luaL_typerror(L, narg, className);
 
-	return *(LuaPerlinNoiseMap **)ud;  // unbox pointer
+	return *(LuaPerlinNoiseMap **)ud;
 }
 
 
@@ -307,7 +306,7 @@ void LuaPerlinNoiseMap::Register(lua_State *L)
 
 	lua_pushliteral(L, "__metatable");
 	lua_pushvalue(L, methodtable);
-	lua_settable(L, metatable);  // hide metatable from Lua getmetatable()
+	lua_settable(L, metatable);
 
 	lua_pushliteral(L, "__index");
 	lua_pushvalue(L, methodtable);
@@ -317,12 +316,11 @@ void LuaPerlinNoiseMap::Register(lua_State *L)
 	lua_pushcfunction(L, gc_object);
 	lua_settable(L, metatable);
 
-	lua_pop(L, 1);  // drop metatable
+	lua_pop(L, 1);
 
-	luaL_openlib(L, 0, methods, 0);  // fill methodtable
-	lua_pop(L, 1);  // drop methodtable
+	luaL_openlib(L, 0, methods, 0);
+	lua_pop(L, 1);
 
-	// Can be created from Lua (PerlinNoiseMap(np, size)
 	lua_register(L, className, create_object);
 }
 
@@ -336,32 +334,23 @@ const luaL_reg LuaPerlinNoiseMap::methods[] = {
 	{0,0}
 };
 
+///////////////////////////////////////
 /*
 	LuaPseudoRandom
 */
 
-// garbage collector
-int LuaPseudoRandom::gc_object(lua_State *L)
-{
-	LuaPseudoRandom *o = *(LuaPseudoRandom **)(lua_touserdata(L, 1));
-	delete o;
-	return 0;
-}
-
-
-// next(self, min=0, max=32767) -> get next value
 int LuaPseudoRandom::l_next(lua_State *L)
 {
 	NO_MAP_LOCK_REQUIRED;
 	LuaPseudoRandom *o = checkobject(L, 1);
 	int min = 0;
 	int max = 32767;
-	lua_settop(L, 3); // Fill 2 and 3 with nil if they don't exist
-	if(!lua_isnil(L, 2))
+	lua_settop(L, 3);
+	if (lua_isnumber(L, 2))
 		min = luaL_checkinteger(L, 2);
-	if(!lua_isnil(L, 3))
+	if (lua_isnumber(L, 3))
 		max = luaL_checkinteger(L, 3);
-	if(max < min){
+	if (max < min) {
 		errorstream<<"PseudoRandom.next(): max="<<max<<" min="<<min<<std::endl;
 		throw LuaError("PseudoRandom.next(): max < min");
 	}
@@ -378,30 +367,6 @@ int LuaPseudoRandom::l_next(lua_State *L)
 }
 
 
-LuaPseudoRandom::LuaPseudoRandom(int seed):
-	m_pseudo(seed)
-{
-}
-
-
-LuaPseudoRandom::~LuaPseudoRandom()
-{
-}
-
-
-const PseudoRandom& LuaPseudoRandom::getItem() const
-{
-	return m_pseudo;
-}
-
-PseudoRandom& LuaPseudoRandom::getItem()
-{
-	return m_pseudo;
-}
-
-
-// LuaPseudoRandom(seed)
-// Creates an LuaPseudoRandom and leaves it on top of stack
 int LuaPseudoRandom::create_object(lua_State *L)
 {
 	int seed = luaL_checknumber(L, 1);
@@ -413,13 +378,21 @@ int LuaPseudoRandom::create_object(lua_State *L)
 }
 
 
-LuaPseudoRandom* LuaPseudoRandom::checkobject(lua_State *L, int narg)
+int LuaPseudoRandom::gc_object(lua_State *L)
+{
+	LuaPseudoRandom *o = *(LuaPseudoRandom **)(lua_touserdata(L, 1));
+	delete o;
+	return 0;
+}
+
+
+LuaPseudoRandom *LuaPseudoRandom::checkobject(lua_State *L, int narg)
 {
 	luaL_checktype(L, narg, LUA_TUSERDATA);
 	void *ud = luaL_checkudata(L, narg, className);
 	if (!ud)
 		luaL_typerror(L, narg, className);
-	return *(LuaPseudoRandom**)ud;  // unbox pointer
+	return *(LuaPseudoRandom **)ud;
 }
 
 
@@ -432,7 +405,7 @@ void LuaPseudoRandom::Register(lua_State *L)
 
 	lua_pushliteral(L, "__metatable");
 	lua_pushvalue(L, methodtable);
-	lua_settable(L, metatable);  // hide metatable from Lua getmetatable()
+	lua_settable(L, metatable);
 
 	lua_pushliteral(L, "__index");
 	lua_pushvalue(L, methodtable);
@@ -442,12 +415,11 @@ void LuaPseudoRandom::Register(lua_State *L)
 	lua_pushcfunction(L, gc_object);
 	lua_settable(L, metatable);
 
-	lua_pop(L, 1);  // drop metatable
+	lua_pop(L, 1);
 
-	luaL_openlib(L, 0, methods, 0);  // fill methodtable
-	lua_pop(L, 1);  // drop methodtable
+	luaL_openlib(L, 0, methods, 0);
+	lua_pop(L, 1);
 
-	// Can be created from Lua (LuaPseudoRandom(seed))
 	lua_register(L, className, create_object);
 }
 
@@ -457,3 +429,101 @@ const luaL_reg LuaPseudoRandom::methods[] = {
 	luamethod(LuaPseudoRandom, next),
 	{0,0}
 };
+
+///////////////////////////////////////
+/*
+	LuaPcgRandom
+*/
+
+int LuaPcgRandom::l_next(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+
+	LuaPcgRandom *o = checkobject(L, 1);
+	u32 min = lua_isnumber(L, 2) ? lua_tointeger(L, 2) : o->m_rnd.RANDOM_MIN;
+	u32 max = lua_isnumber(L, 3) ? lua_tointeger(L, 3) : o->m_rnd.RANDOM_MAX;
+
+	lua_pushinteger(L, o->m_rnd.range(min, max));
+	return 1;
+}
+
+
+int LuaPcgRandom::l_rand_normal_dist(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+
+	LuaPcgRandom *o = checkobject(L, 1);
+	u32 min = lua_isnumber(L, 2) ? lua_tointeger(L, 2) : o->m_rnd.RANDOM_MIN;
+	u32 max = lua_isnumber(L, 3) ? lua_tointeger(L, 3) : o->m_rnd.RANDOM_MAX;
+	int num_trials = lua_isnumber(L, 4) ? lua_tointeger(L, 4) : 6;
+
+	lua_pushinteger(L, o->m_rnd.randNormalDist(min, max, num_trials));
+	return 1;
+}
+
+
+int LuaPcgRandom::create_object(lua_State *L)
+{
+	lua_Integer seed = luaL_checknumber(L, 1);
+	LuaPcgRandom *o  = lua_isnumber(L, 2) ?
+		new LuaPcgRandom(seed, lua_tointeger(L, 2)) :
+		new LuaPcgRandom(seed);
+	*(void **)(lua_newuserdata(L, sizeof(void *))) = o;
+	luaL_getmetatable(L, className);
+	lua_setmetatable(L, -2);
+	return 1;
+}
+
+
+int LuaPcgRandom::gc_object(lua_State *L)
+{
+	LuaPcgRandom *o = *(LuaPcgRandom **)(lua_touserdata(L, 1));
+	delete o;
+	return 0;
+}
+
+
+LuaPcgRandom *LuaPcgRandom::checkobject(lua_State *L, int narg)
+{
+	luaL_checktype(L, narg, LUA_TUSERDATA);
+	void *ud = luaL_checkudata(L, narg, className);
+	if (!ud)
+		luaL_typerror(L, narg, className);
+	return *(LuaPcgRandom **)ud;
+}
+
+
+void LuaPcgRandom::Register(lua_State *L)
+{
+	lua_newtable(L);
+	int methodtable = lua_gettop(L);
+	luaL_newmetatable(L, className);
+	int metatable = lua_gettop(L);
+
+	lua_pushliteral(L, "__metatable");
+	lua_pushvalue(L, methodtable);
+	lua_settable(L, metatable);
+
+	lua_pushliteral(L, "__index");
+	lua_pushvalue(L, methodtable);
+	lua_settable(L, metatable);
+
+	lua_pushliteral(L, "__gc");
+	lua_pushcfunction(L, gc_object);
+	lua_settable(L, metatable);
+
+	lua_pop(L, 1);
+
+	luaL_openlib(L, 0, methods, 0);
+	lua_pop(L, 1);
+
+	lua_register(L, className, create_object);
+}
+
+
+const char LuaPcgRandom::className[] = "PcgRandom";
+const luaL_reg LuaPcgRandom::methods[] = {
+	luamethod(LuaPcgRandom, next),
+	luamethod(LuaPcgRandom, rand_normal_dist),
+	{0,0}
+};

src/script/lua_api/l_noise.h

@@ -64,6 +64,9 @@ class LuaPerlinNoiseMap : public ModApiBase {
 	static const char className[];
 	static const luaL_reg methods[];
 
+	// Exported functions
+
+	// garbage collector
 	static int gc_object(lua_State *L);
 
 	static int l_get2dMap(lua_State *L);
@@ -104,18 +107,51 @@ private:
 	static int l_next(lua_State *L);
 
 public:
-	LuaPseudoRandom(int seed);
-
-	~LuaPseudoRandom();
-
-	const PseudoRandom& getItem() const;
-	PseudoRandom& getItem();
+	LuaPseudoRandom(int seed) :
+		m_pseudo(seed) {}
 
 	// LuaPseudoRandom(seed)
 	// Creates an LuaPseudoRandom and leaves it on top of stack
 	static int create_object(lua_State *L);
 
-	static LuaPseudoRandom* checkobject(lua_State *L, int narg);
+	static LuaPseudoRandom *checkobject(lua_State *L, int narg);
+
+	static void Register(lua_State *L);
+};
+
+/*
+	LuaPcgRandom
+*/
+class LuaPcgRandom : public ModApiBase {
+private:
+	PcgRandom m_rnd;
+
+	static const char className[];
+	static const luaL_reg methods[];
+
+	// Exported functions
+
+	// garbage collector
+	static int gc_object(lua_State *L);
+
+	// next(self, min=-2147483648, max=2147483647) -> get next value
+	static int l_next(lua_State *L);
+
+	// rand_normal_dist(self, min=-2147483648, max=2147483647, num_trials=6) ->
+	// get next normally distributed random value
+	static int l_rand_normal_dist(lua_State *L);
+
+public:
+	LuaPcgRandom(u64 seed) :
+		m_rnd(seed) {}
+	LuaPcgRandom(u64 seed, u64 seq) :
+		m_rnd(seed, seq) {}
+
+	// LuaPcgRandom(seed)
+	// Creates an LuaPcgRandom and leaves it on top of stack
+	static int create_object(lua_State *L);
+
+	static LuaPcgRandom *checkobject(lua_State *L, int narg);
 
 	static void Register(lua_State *L);
 };

src/script/scripting_game.cpp

@@ -92,6 +92,7 @@ void GameScripting::InitializeModApi(lua_State *L, int top)
 	LuaPerlinNoise::Register(L);
 	LuaPerlinNoiseMap::Register(L);
 	LuaPseudoRandom::Register(L);
+	LuaPcgRandom::Register(L);
 	LuaVoxelManip::Register(L);
 	NodeMetaRef::Register(L);
 	NodeTimerRef::Register(L);

src/util/numeric.cpp

@@ -22,6 +22,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #include "log.h"
 #include "../constants.h" // BS, MAP_BLOCKSIZE
+#include "../noise.h" // PseudoRandom, PcgRandom
 #include <string.h>
 #include <iostream>
 
@@ -115,36 +116,32 @@ void FacePositionCache::generateFacePosition(u16 d)
     myrand
 */
 
-static unsigned long next = 1;
+PcgRandom g_pcgrand;
 
-/* RAND_MAX assumed to be 32767 */
-int myrand(void)
+u32 myrand()
 {
-   next = next * 1103515245 + 12345;
-   return((unsigned)(next/65536) % 32768);
+	return g_pcgrand.next();
 }
 
-void mysrand(unsigned seed)
+void mysrand(unsigned int seed)
 {
-   next = seed;
+	g_pcgrand.seed(seed);
+}
+
+void myrand_bytes(void *out, size_t len)
+{
+	g_pcgrand.bytes(out, len);
 }
 
 int myrand_range(int min, int max)
 {
-	if(max-min > MYRAND_MAX)
-	{
-		errorstream<<"WARNING: myrand_range: max-min > MYRAND_MAX"<<std::endl;
-        max = min + MYRAND_MAX;
-	}
-	if(min > max)
-	{
-		errorstream<<"WARNING: myrand_range: min > max"<<std::endl;
-		return max;
-	}
-	return (myrand()%(max-min+1))+min;
+	return g_pcgrand.range(min, max);
 }
 
-// 64-bit unaligned version of MurmurHash
+
+/*
+	64-bit unaligned version of MurmurHash
+*/
 u64 murmur_hash_64_ua(const void *key, int len, unsigned int seed)
 {
 	const u64 m = 0xc6a4a7935bd1e995ULL;
@@ -159,12 +156,12 @@ u64 murmur_hash_64_ua(const void *key, int len, unsigned int seed)
 		memcpy(&k, data, sizeof(u64));
 		data++;
 
-		k *= m; 
-		k ^= k >> r; 
-		k *= m; 
-		
+		k *= m;
+		k ^= k >> r;
+		k *= m;
+
 		h ^= k;
-		h *= m; 
+		h *= m;
 	}
 
 	const unsigned char *data2 = (const unsigned char *)data;
@@ -178,13 +175,13 @@ u64 murmur_hash_64_ua(const void *key, int len, unsigned int seed)
 		case 1: h ^= (u64)data2[0];
 				h *= m;
 	}
- 
+
 	h ^= h >> r;
 	h *= m;
 	h ^= h >> r;
-	
+
 	return h;
-} 
+}
 
 
 /*
@@ -197,7 +194,7 @@ bool isBlockInSight(v3s16 blockpos_b, v3f camera_pos, v3f camera_dir,
 		f32 camera_fov, f32 range, f32 *distance_ptr)
 {
 	v3s16 blockpos_nodes = blockpos_b * MAP_BLOCKSIZE;
-	
+
 	// Block center position
 	v3f blockpos(
 			((float)blockpos_nodes.X + MAP_BLOCKSIZE/2) * BS,
@@ -213,7 +210,7 @@ bool isBlockInSight(v3s16 blockpos_b, v3f camera_pos, v3f camera_dir,
 
 	if(distance_ptr)
 		*distance_ptr = d;
-	
+
 	// If block is far away, it's not in sight
 	if(d > range)
 		return false;
@@ -221,7 +218,7 @@ bool isBlockInSight(v3s16 blockpos_b, v3f camera_pos, v3f camera_dir,
 	// Maximum radius of a block.  The magic number is
 	// sqrt(3.0) / 2.0 in literal form.
 	f32 block_max_radius = 0.866025403784 * MAP_BLOCKSIZE * BS;
-	
+
 	// If block is (nearly) touching the camera, don't
 	// bother validating further (that is, render it anyway)
 	if(d < block_max_radius)
@@ -242,7 +239,7 @@ bool isBlockInSight(v3s16 blockpos_b, v3f camera_pos, v3f camera_dir,
 	// Cosine of the angle between the camera direction
 	// and the block direction (camera_dir is an unit vector)
 	f32 cosangle = dforward / blockpos_adj.getLength();
-	
+
 	// If block is not in the field of view, skip it
 	if(cosangle < cos(camera_fov / 2))
 		return false;

src/util/numeric.h

@@ -239,10 +239,10 @@ inline float wrapDegrees_180(float f)
 /*
 	Pseudo-random (VC++ rand() sucks)
 */
-int myrand(void);
-void mysrand(unsigned seed);
-#define MYRAND_MAX 32767
-
+#define MYRAND_RANGE 0xffffffff
+u32 myrand();
+void mysrand(unsigned int seed);
+void myrand_bytes(void *out, size_t len);
 int myrand_range(int min, int max);
 
 /*