Use 'pcg64_fast' for RNG

This is a higher quality source of randomness than a XOR-shift
generator, while still being fast and easy to write.

src/movegen/wizardry/mod.rs

@@ -60,138 +60,138 @@ impl MagicMoves {
 // region:sourcegen
 /// A set of magic numbers for bishop move generation.
 pub(crate) const BISHOP_SEED: [u64; Square::NUM_VARIANTS] = [
-    4908958787341189172,
-    1157496606860279808,
-    289395876198088778,
-    649648646467355137,
-    19162426089930848,
-    564067194896448,
-    18586170375029026,
-    9185354800693760,
-    72172012436987968,
-    317226351607872,
-    2597178509285688384,
-    1162205282238464,
-    144154788211329152,
-    172197832046936160,
-    4625762105940000802,
-    1477217245166903296,
-    2251937789583872,
-    289373902621379585,
-    4616200855845409024,
-    2251909637357568,
-    3532510975437640064,
-    563517968228352,
-    562953309660434,
-    1196005458310201856,
-    2350914225914520576,
-    2287018679861376,
-    13836188353273790593,
-    11267795163676832,
-    297519119119499264,
-    18588344158519552,
-    10453428171813953792,
-    72128237668534272,
-    1298164929055953920,
-    865575144395900952,
-    9293076573325312,
-    108104018148197376,
-    578503662094123152,
-    4665870505495102224,
-    6066493872259301520,
-    285877477613857,
-    2328941618281318466,
-    721165292771739652,
-    4899973577790523400,
-    75050392749184,
-    2305878200632215680,
-    11530099074925593616,
-    290561512873919880,
-    18652187227888000,
-    3379933716168704,
-    9223409493537718272,
-    22273835729926,
-    1152921524003672064,
-    4647812741240848385,
-    1244225087719112712,
-    7367907171013001728,
-    9263922034316951570,
-    300758214358598160,
-    4611686331973636096,
-    2377900605806479360,
-    6958097192913601024,
-    864691130877743617,
-    703824948904066,
-    612700674899317536,
-    180742128018784384,
+    4634226011293351952,
+    6918109887683821586,
+    76562328660738184,
+    7242919606867744800,
+    13871652069997347969,
+    1171657252671901696,
+    147001475087730752,
+    1752045392763101248,
+    288406435526639744,
+    4612213818402029888,
+    9808848818951710728,
+    9223394181731320840,
+    54047645651435648,
+    9224780030482579712,
+    9049059098626048,
+    1442330840700035221,
+    1126037887157508,
+    1153488887004529665,
+    290485130928332936,
+    9226749771011592258,
+    148636405693678112,
+    2260596997758984,
+    73470481646424336,
+    2341907012146823680,
+    2314955761652335121,
+    2265544246165632,
+    13598764778463296,
+    563087425962496,
+    563087425962048,
+    2163991853573081088,
+    567353402270020,
+    6488844433713538048,
+    288810987011448834,
+    11830884701569344,
+    2747549955031826688,
+    35734665298432,
+    18025943920672800,
+    292892945404789012,
+    1153520472160470528,
+    2260949167801860,
+    155446765112299521,
+    379008324189818944,
+    4616480181217005576,
+    576461027453960704,
+    2450556349601564416,
+    1160556519943569536,
+    4612900059821375552,
+    5477089643453251617,
+    9223532084785594632,
+    2810391870219355200,
+    36594222015453185,
+    4612011546951352320,
+    2392883590201344,
+    1152956706186200064,
+    9009415592510464,
+    81077999302148128,
+    576746627483043968,
+    301267327789056,
+    39586720976896,
+    720878306081243648,
+    9223512777841312257,
+    5764609859566698625,
+    8088544233436348496,
+    4612856276794474560,
 ];
 
 /// A set of magic numbers for rook move generation.
 pub(crate) const ROOK_SEED: [u64; Square::NUM_VARIANTS] = [
-    2341871943948451840,
-    18015635528220736,
-    72066665545773824,
-    1188959097794342912,
-    12141713393631625314,
-    720649693658353672,
-    36029896538981888,
-    36033359356363520,
-    140746619355268,
-    1158339898446446661,
-    36591886560003650,
-    578853633228023808,
-    2392554490300416,
-    140814806160384,
-    180706952366596608,
-    10696087878779396,
-    1153260703948210820,
-    310748649170673678,
-    36311372044308544,
-    9223444604757615104,
-    1267187285230592,
-    282574622818306,
-    18722484274726152,
-    2271591090110593,
-    1153063519847989248,
-    10168327557107712,
-    4507998211276833,
-    1153203035420233728,
-    4631961017139660032,
-    2454499182462107776,
-    289367288355753288,
-    18015815850820609,
-    9268726066908758912,
-    11547264697673728000,
-    2314929519368081536,
-    140943655192577,
-    20266215511427202,
-    180706969441535248,
-    1302683805944911874,
-    11534000122299940994,
-    22676602724843520,
-    4639271120198041668,
-    1302104069046927376,
-    9184220895313928,
-    4612249105954373649,
-    562984581726212,
-    2312678200579457040,
-    4647736876550193157,
-    3170604524138139776,
-    4684447574787096704,
-    20283792725901696,
-    1152992019380963840,
-    117383863558471808,
-    1153488854922068096,
-    17596884583424,
-    90074759127192064,
-    4900502436426416706,
-    4573968656793901,
-    1161084564408385,
-    1657887889314811910,
-    4614501455660058690,
-    4612530729109422081,
-    642458506527236,
-    1116704154754,
+    180144122814791812,
+    10448386594766422036,
+    9403533616331358856,
+    108095189301858304,
+    72076290316044288,
+    36066182562054145,
+    4647717564258980096,
+    13979173385364603396,
+    4620833992751489152,
+    297800804633419904,
+    578009002156298240,
+    2450099003505838082,
+    1175721046778052864,
+    20406952999780864,
+    1175861788231598592,
+    36169538802827392,
+    288371663414771712,
+    423313050501155,
+    604731668136450,
+    580261214513399808,
+    297661437206136832,
+    1750211954976489600,
+    9020393411186696,
+    9259543770406356001,
+    44532368556032,
+    10376381507760693256,
+    52778707714176,
+    4612829512676149248,
+    1882513444629184528,
+    2369460754144428160,
+    9223380850137104901,
+    2666413562481640036,
+    141012643087392,
+    16735517094631719424,
+    17594358702087,
+    2344264412262574084,
+    422813768878080,
+    1126450811896320,
+    54466576291772936,
+    42784758060548372,
+    292874851780165648,
+    18015364885839937,
+    282644818493504,
+    1184447393488764944,
+    4649966632473477184,
+    563499910594566,
+    17632049496086,
+    18502729728001,
+    140742121013504,
+    9711024139665536,
+    246293205270784,
+    290772515771392256,
+    9230131836490350720,
+    73326432604127360,
+    453174886517643776,
+    2396271245728563712,
+    324259242966026501,
+    288953994406543363,
+    1153557061259362338,
+    40533496293515441,
+    1407392197644307,
+    1729945211427624002,
+    587808330812164100,
+    9511606812128903298,
 ];
 // endregion:sourcegen
 

src/utils/rand.rs

@@ -3,21 +3,25 @@ pub trait RandGen {
     fn gen(&mut self) -> u64;
 }
 
-// A simple XOR-shift RNG implementation, for code-generation.
+// A simple pcg64_fast RNG implementation, for code-generation.
 #[cfg(test)]
-pub struct SimpleRng(u64);
+pub struct SimpleRng(u128);
 
 #[cfg(test)]
 impl SimpleRng {
     pub fn new() -> Self {
-        Self(4) // https://xkcd.com/221/
+        Self(0xcafef00dd15ea5e5 | 1) // https://xkcd.com/221/
     }
 
     pub fn gen(&mut self) -> u64 {
-        self.0 ^= self.0 >> 12;
-        self.0 ^= self.0 << 25;
-        self.0 ^= self.0 >> 27;
-        self.0
+        const MULTIPLIER: u128 = 0x2360_ED05_1FC6_5DA4_4385_DF64_9FCC_F645;
+        const XSHIFT: u32 = 64; // (128 - 64 + 64) / 2
+        const ROTATE: u32 = 122; // 128 - 6
+
+        self.0 = self.0.wrapping_mul(MULTIPLIER);
+        let rot = (self.0 >> ROTATE) as u32;
+        let xsl = (self.0 >> XSHIFT) as u64 ^ (self.0 as u64);
+        xsl.rotate_right(rot)
     }
 }
 
@@ -36,10 +40,10 @@ mod test {
     fn rng() {
         let mut rng = SimpleRng::new();
 
-        assert_eq!(rng.gen(), 134217733);
-        assert_eq!(rng.gen(), 4504699139039237);
-        assert_eq!(rng.gen(), 13512173405898766);
-        assert_eq!(rng.gen(), 9225626310854853124);
-        assert_eq!(rng.gen(), 29836777971867270);
+        assert_eq!(rng.gen(), 64934999470316615);
+        assert_eq!(rng.gen(), 15459456780870779090);
+        assert_eq!(rng.gen(), 13715484424881807779);
+        assert_eq!(rng.gen(), 17718572936700675021);
+        assert_eq!(rng.gen(), 14587996314750246637);
     }
 }