forked from Mirrorlandia_minetest/minetest
Simplify LuaPseudoRandom::l_next and fix docs
Also extends the allowed range on the C++ side. This has no side-effects.
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@ -8061,7 +8061,9 @@ A 32-bit pseudorandom number generator.
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Uses PCG32, an algorithm of the permuted congruential generator family,
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offering very strong randomness.
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It can be created via `PcgRandom(seed)` or `PcgRandom(seed, sequence)`.
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* constructor `PcgRandom(seed, [seq])`
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* `seed`: 64-bit unsigned seed
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* `seq`: 64-bit unsigned sequence, optional
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### Methods
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@ -8156,14 +8158,15 @@ Can be obtained using `player:get_meta()`.
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A 16-bit pseudorandom number generator.
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Uses a well-known LCG algorithm introduced by K&R.
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It can be created via `PseudoRandom(seed)`.
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* constructor `PseudoRandom(seed)`
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* `seed`: 32-bit signed number
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### Methods
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* `next()`: return next integer random number [`0`...`32767`]
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* `next(min, max)`: return next integer random number [`min`...`max`]
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* `((max - min) == 32767) or ((max-min) <= 6553))` must be true
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due to the simple implementation making bad distribution otherwise.
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* Either `max - min == 32767` or `max - min <= 6553` must be true
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due to the simple implementation making a bad distribution otherwise.
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`Raycast`
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---------
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@ -6,6 +6,8 @@ local function test_random()
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local pr2 = PseudoRandom(-101)
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assert(pr2:next(0, 100) == 35)
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-- unusual case that is normally disallowed:
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assert(pr2:next(10000, 42767) == 12485)
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end
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unittests.register("test_random", test_random)
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@ -70,7 +70,7 @@ public:
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PcgRandom, we cannot modify this RNG's range as it would change the
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output of this RNG for reverse compatibility.
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*/
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if ((u32)(max - min) > (RANDOM_RANGE + 1) / 10)
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if ((u32)(max - min) > (RANDOM_RANGE + 1) / 5)
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throw PrngException("Range too large");
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return (next() % (max - min + 1)) + min;
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@ -405,25 +405,22 @@ int LuaPseudoRandom::l_next(lua_State *L)
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NO_MAP_LOCK_REQUIRED;
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LuaPseudoRandom *o = checkObject<LuaPseudoRandom>(L, 1);
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int min = 0;
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int max = 32767;
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lua_settop(L, 3);
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int min = 0, max = PseudoRandom::RANDOM_RANGE;
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if (lua_isnumber(L, 2))
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min = luaL_checkinteger(L, 2);
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if (lua_isnumber(L, 3))
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max = luaL_checkinteger(L, 3);
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if (max < min) {
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errorstream<<"PseudoRandom.next(): max="<<max<<" min="<<min<<std::endl;
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throw LuaError("PseudoRandom.next(): max < min");
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int val;
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if (max - min == PseudoRandom::RANDOM_RANGE) {
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val = o->m_pseudo.next() + min;
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} else {
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try {
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val = o->m_pseudo.range(min, max);
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} catch (PrngException &e) {
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throw LuaError(e.what());
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}
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}
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if(max - min != 32767 && max - min > 32767/5)
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throw LuaError("PseudoRandom.next() max-min is not 32767"
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" and is > 32768/5. This is disallowed due to"
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" the bad random distribution the"
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" implementation would otherwise make.");
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PseudoRandom &pseudo = o->m_pseudo;
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int val = pseudo.next();
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val = (val % (max-min+1)) + min;
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lua_pushinteger(L, val);
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return 1;
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}
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@ -81,7 +81,7 @@ void TestRandom::testPseudoRandomRange()
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{
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PseudoRandom pr((int)time(NULL));
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EXCEPTION_CHECK(PrngException, pr.range(2000, 6000));
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EXCEPTION_CHECK(PrngException, pr.range(2000, 8600));
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EXCEPTION_CHECK(PrngException, pr.range(5, 1));
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for (u32 i = 0; i != 32768; i++) {
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