From 2bf775febda59c7da46283d387e0d6803fd91901 Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Wed, 20 Dec 2023 13:56:20 -0600
Subject: [PATCH 01/18] High-quality RNG, behind a flag. HQ_RANDOM enabled by
 default for testing purposes.

---
 include/battle.h                      |  13 +++
 include/contest.h                     |   3 +-
 include/random.h                      |  80 +++++++++++++++++--
 include/recorded_battle.h             |   7 +-
 src/battle_controller_link_opponent.c |   1 +
 src/battle_controller_link_partner.c  |   1 +
 src/battle_main.c                     |   9 ++-
 src/contest.c                         |   5 +-
 src/contest_util.c                    |   6 +-
 src/main.c                            |   2 +-
 src/random.c                          | 111 ++++++++++++++++++++++++--
 src/recorded_battle.c                 |   4 +-
 12 files changed, 213 insertions(+), 29 deletions(-)

diff --git a/include/battle.h b/include/battle.h
index e78434578813..156b84099789 100644
--- a/include/battle.h
+++ b/include/battle.h
@@ -15,6 +15,7 @@
 #include "pokeball.h"
 #include "battle_debug.h"
 #include "battle_dynamax.h"
+#include "random.h" // for HQ_RANDOM
 
 // Used to exclude moves learned temporarily by Transform or Mimic
 #define MOVE_IS_PERMANENT(battler, moveSlot)                        \
@@ -579,6 +580,13 @@ struct LostItem
     u16 stolen:1;
 };
 
+#if HQ_RANDOM == 1
+struct BattleVideo {
+    u32 battleTypeFlags;
+    rng_value_t rngSeed;
+};
+#endif
+
 struct BattleStruct
 {
     u8 turnEffectsTracker;
@@ -650,7 +658,12 @@ struct BattleStruct
     u16 lastTakenMoveFrom[MAX_BATTLERS_COUNT][MAX_BATTLERS_COUNT]; // a 2-D array [target][attacker]
     union {
         struct LinkBattlerHeader linkBattlerHeader;
+
+        #if HQ_RANDOM == 0
         u32 battleVideo[2];
+        #else
+        struct BattleVideo battleVideo;
+        #endif
     } multiBuffer;
     u8 wishPerishSongState;
     u8 wishPerishSongBattlerId;
diff --git a/include/contest.h b/include/contest.h
index 21e2530c2114..7a67fecd55a7 100644
--- a/include/contest.h
+++ b/include/contest.h
@@ -3,6 +3,7 @@
 
 #include "palette.h"
 #include "constants/contest.h"
+#include "random.h" // for rng_value_t
 
 enum
 {
@@ -327,7 +328,7 @@ extern struct ContestResources *gContestResources;
 extern struct ContestWinner gCurContestWinner;
 extern u8 gCurContestWinnerIsForArtist;
 extern u8 gCurContestWinnerSaveIdx;
-extern u32 gContestRngValue;
+extern rng_value_t gContestRngValue;
 
 // contest.c
 void ResetLinkContestBoolean(void);
diff --git a/include/random.h b/include/random.h
index c3d6067efaa1..0d3cf710698f 100644
--- a/include/random.h
+++ b/include/random.h
@@ -1,8 +1,64 @@
 #ifndef GUARD_RANDOM_H
 #define GUARD_RANDOM_H
 
-extern u32 gRngValue;
-extern u32 gRng2Value;
+// The number 1103515245 comes from the example implementation of rand and srand
+// in the ISO C standard.
+#define ISO_RANDOMIZE1(val)(1103515245 * (val) + 24691)
+#define ISO_RANDOMIZE2(val)(1103515245 * (val) + 12345)
+
+// If 1, use a high-quality PRNG.
+// This may break existing projects.
+#define HQ_RANDOM    1
+
+/* Notes about new functions:
+* If using HQ_RANDOM, you MUST call AdvanceRandom() in VBlank handlers.
+* If you do not, you risk corruption of the RNG state.
+* LocalRandom(*val) adapts to either choice of RNG implementation.
+* Other new functions should be self-explanatory.
+*/
+
+#if HQ_RANDOM == 1
+struct Sfc32State {
+    u32 a;
+    u32 b;
+    u32 c;
+    u32 ctr;
+};
+
+typedef struct Sfc32State rng_value_t;
+
+// Calling this function directly is discouraged.
+// Use LocalRandom() instead.
+static inline u32 _SFC32_Next(struct Sfc32State *state)
+{
+    const u32 result = state->a + state->b + state->ctr++;
+    state->a = state->b ^ (state->b >> 9);
+    state->b = state->c * 9;
+    state->c = result + ((state->c << 21) | (state->c >> 11));
+    return result;
+}
+
+static inline u16 LocalRandom(rng_value_t *val)
+{
+    return _SFC32_Next(val) >> 16;
+}
+
+u32 Random32(void);
+u32 Random2_32(void);
+
+static inline u16 Random(void)
+{
+    return Random32() >> 16;
+}
+
+static inline u16 Random2(void)
+{
+    return Random2_32() >> 16;
+}
+
+void AdvanceRandom(void);
+#else
+typedef u32 rng_value_t;
 
 //Returns a 16-bit pseudorandom number
 u16 Random(void);
@@ -10,11 +66,23 @@ u16 Random2(void);
 
 //Returns a 32-bit pseudorandom number
 #define Random32() (Random() | (Random() << 16))
+#define Random2_32() (Random2() | (Random2() << 16))
 
-// The number 1103515245 comes from the example implementation of rand and srand
-// in the ISO C standard.
-#define ISO_RANDOMIZE1(val)(1103515245 * (val) + 24691)
-#define ISO_RANDOMIZE2(val)(1103515245 * (val) + 12345)
+static inline u16 LocalRandom(rng_value_t *val)
+{
+    *val = ISO_RANDOMIZE1(*val);
+    return *val >> 16;
+}
+
+static inline void AdvanceRandom(void)
+{
+    Random();
+}
+
+#endif
+
+extern rng_value_t gRngValue;
+extern rng_value_t gRng2Value;
 
 //Sets the initial seed value of the pseudorandom number generator
 void SeedRng(u16 seed);
diff --git a/include/recorded_battle.h b/include/recorded_battle.h
index fcbe9495fd86..5d3f47d14014 100644
--- a/include/recorded_battle.h
+++ b/include/recorded_battle.h
@@ -2,6 +2,7 @@
 #define GUARD_RECORDED_BATTLE_H
 
 #include "constants/battle.h"
+#include "random.h" // for rng_value_t
 
 #define BATTLER_RECORD_SIZE 664
 
@@ -13,7 +14,7 @@ struct RecordedBattleSave
     u8 playersGender[MAX_BATTLERS_COUNT];
     u32 playersTrainerId[MAX_BATTLERS_COUNT];
     u8 playersLanguage[MAX_BATTLERS_COUNT];
-    u32 rngSeed;
+    rng_value_t rngSeed;
     u32 battleFlags;
     u8 playersBattlers[MAX_BATTLERS_COUNT];
     u16 opponentA;
@@ -49,8 +50,8 @@ enum
     RECORDED_ITEM_MOVE,
 };
 
-extern u32 gRecordedBattleRngSeed;
-extern u32 gBattlePalaceMoveSelectionRngValue;
+extern rng_value_t gRecordedBattleRngSeed;
+extern rng_value_t gBattlePalaceMoveSelectionRngValue;
 extern u8 gRecordedBattleMultiplayerId;
 
 #define B_RECORD_MODE_RECORDING 1
diff --git a/src/battle_controller_link_opponent.c b/src/battle_controller_link_opponent.c
index 3a3cb7e8ce33..f01f5da1e353 100644
--- a/src/battle_controller_link_opponent.c
+++ b/src/battle_controller_link_opponent.c
@@ -28,6 +28,7 @@
 #include "constants/songs.h"
 #include "constants/trainers.h"
 #include "recorded_battle.h"
+#include "random.h" // for rng_value_t
 
 static void LinkOpponentHandleLoadMonSprite(u32 battler);
 static void LinkOpponentHandleSwitchInAnim(u32 battler);
diff --git a/src/battle_controller_link_partner.c b/src/battle_controller_link_partner.c
index 4b8daeb1e1fd..b0256874374a 100644
--- a/src/battle_controller_link_partner.c
+++ b/src/battle_controller_link_partner.c
@@ -28,6 +28,7 @@
 #include "constants/songs.h"
 #include "constants/trainers.h"
 #include "recorded_battle.h"
+#include "random.h" // for rng_value_t
 
 static void LinkPartnerHandleLoadMonSprite(u32 battler);
 static void LinkPartnerHandleSwitchInAnim(u32 battler);
diff --git a/src/battle_main.c b/src/battle_main.c
index 0f708d41ee59..f9bdb7595a6c 100644
--- a/src/battle_main.c
+++ b/src/battle_main.c
@@ -1712,9 +1712,16 @@ static void CB2_HandleStartMultiBattle(void)
     case 8:
         if (IsLinkTaskFinished())
         {
+            #if HQ_RANDOM == 1
+            struct BattleVideo *ptr = &gBattleStruct->multiBuffer.battleVideo;
+            ptr->battleTypeFlags = gBattleTypeFlags;
+            ptr->rngSeed = gRecordedBattleRngSeed;
+            #else
             u32 *ptr = gBattleStruct->multiBuffer.battleVideo;
             ptr[0] = gBattleTypeFlags;
             ptr[1] = gRecordedBattleRngSeed; // UB: overwrites berry data
+            #endif
+
             SendBlock(BitmaskAllOtherLinkPlayers(), ptr, sizeof(gBattleStruct->multiBuffer.battleVideo));
             gBattleCommunication[MULTIUSE_STATE]++;
         }
@@ -2052,7 +2059,7 @@ void VBlankCB_Battle(void)
 {
     // Change gRngSeed every vblank unless the battle could be recorded.
     if (!(gBattleTypeFlags & (BATTLE_TYPE_LINK | BATTLE_TYPE_FRONTIER | BATTLE_TYPE_RECORDED)))
-        Random();
+        AdvanceRandom();
 
     SetGpuReg(REG_OFFSET_BG0HOFS, gBattle_BG0_X);
     SetGpuReg(REG_OFFSET_BG0VOFS, gBattle_BG0_Y);
diff --git a/src/contest.c b/src/contest.c
index 8f452b092168..d4cc73677cc4 100644
--- a/src/contest.c
+++ b/src/contest.c
@@ -358,7 +358,7 @@ EWRAM_DATA bool8 gCurContestWinnerIsForArtist = 0;
 EWRAM_DATA u8 gCurContestWinnerSaveIdx = 0;
 
 // IWRAM common vars.
-u32 gContestRngValue;
+rng_value_t gContestRngValue;
 
 extern const u8 gText_LinkStandby4[];
 extern const u8 gText_BDot[];
@@ -1709,7 +1709,7 @@ static void Task_AppealSetup(u8 taskId)
     if (++gTasks[taskId].data[0] > 19)
     {
         eContest.turnNumber = 0;
-        eContest.unusedRng = gRngValue;
+        eContest.unusedRng = 0;
         if ((gLinkContestFlags & LINK_CONTEST_FLAG_IS_LINK) && IsPlayerLinkLeader())
         {
             s32 i;
@@ -6109,4 +6109,3 @@ void StripPlayerAndMonNamesForLinkContest(struct ContestPokemon *mon, s32 langua
         name[PLAYER_NAME_LENGTH] = EOS;
     }
 }
-
diff --git a/src/contest_util.c b/src/contest_util.c
index 3bd1c2829357..32588a8c00dd 100644
--- a/src/contest_util.c
+++ b/src/contest_util.c
@@ -2655,8 +2655,7 @@ void GenerateContestRand(void)
 
     if (gLinkContestFlags & LINK_CONTEST_FLAG_IS_LINK)
     {
-        gContestRngValue = ISO_RANDOMIZE1(gContestRngValue);
-        random = gContestRngValue >> 16;
+        random = LocalRandom(&gContestRngValue);
         result = &gSpecialVar_Result;
     }
     else
@@ -2669,8 +2668,7 @@ void GenerateContestRand(void)
 
 u16 GetContestRand(void)
 {
-    gContestRngValue = ISO_RANDOMIZE1(gContestRngValue);
-    return gContestRngValue >> 16;
+    return LocalRandom(&gContestRngValue);
 }
 
 bool8 LinkContestWaitForConnection(void)
diff --git a/src/main.c b/src/main.c
index d850bc27bc9c..537af7191b02 100644
--- a/src/main.c
+++ b/src/main.c
@@ -373,7 +373,7 @@ static void VBlankIntr(void)
     TryReceiveLinkBattleData();
 
     if (!gMain.inBattle || !(gBattleTypeFlags & (BATTLE_TYPE_LINK | BATTLE_TYPE_FRONTIER | BATTLE_TYPE_RECORDED)))
-        Random();
+        AdvanceRandom();
 
     UpdateWirelessStatusIndicatorSprite();
 
diff --git a/src/random.c b/src/random.c
index 6a462004b4c3..54c61db99eee 100644
--- a/src/random.c
+++ b/src/random.c
@@ -4,13 +4,93 @@
 #include <alloca.h>
 #endif
 
+// IWRAM common
+rng_value_t gRngValue;
+rng_value_t gRng2Value;
+
+#if HQ_RANDOM == 1
+EWRAM_DATA static volatile u8 sUnknown = 11;
+#define RNG_LOCK sUnknown
+
+
+static void SFC32_Seed(struct Sfc32State *state, u16 seed)
+{
+    u32 i;
+    state->a = state->b = 0;
+    state->c = seed;
+    state->ctr = 1;
+    for(i = 0; i < 16; i++)
+    {
+        _SFC32_Next(state);
+    }
+}
+
+u32 NAKED Random32(void)
+{
+    asm(".thumb\n\
+    push {r4, r5, r6, r7}\n\
+    ldr r7, =sUnknown\n\
+    mov r6, #11\n\
+    strb r6, [r7]\n\
+    ldr r5, =gRngValue\n\
+    ldmia r5!, {r1, r2, r3, r4}\n\
+    @ e (result) = a + b + d++\n\
+    add r1, r1, r2\n\
+    add r0, r1, r4\n\
+    add r4, r4, #1\n\
+    @ a = b ^ (b >> 9)\n\
+    lsr r1, r2, #9\n\
+    eor r1, r1, r2\n\
+    @ b = c + (c << 3) [c * 9]\n\
+    lsl r2, r3, #3\n\
+    add r2, r2, r3\n\
+    @ c = rol(c, 21) + e\n\
+    ror r3, r3, r6\n\
+    add r3, r3, r0\n\
+    sub r5, r5, #16\n\
+    stmia r5!, {r1, r2, r3, r4}\n\
+    mov r1, #0\n\
+    strb r1, [r7]\n\
+    pop {r4, r5, r6, r7}\n\
+    bx lr\n\
+    .ltorg"
+    );
+}
+
+u32 Random2_32(void)
+{
+    return _SFC32_Next(&gRng2Value);
+}
+
+void SeedRng(u16 seed)
+{
+    SFC32_Seed(&gRngValue, seed);
+    RNG_LOCK = 0;
+}
+
+void SeedRng2(u16 seed)
+{
+    SFC32_Seed(&gRng2Value, seed);
+}
+
+void AdvanceRandom(void)
+{
+    if (RNG_LOCK == 0)
+        _SFC32_Next(&gRngValue);
+}
+
+#define LOOP_RANDOM_START \
+    struct Sfc32State *const state = &gRngValue; \
+    RNG_LOCK = 11
+
+#define LOOP_RANDOM_END RNG_LOCK = 0
+
+#define LOOP_RANDOM ((u16)(_SFC32_Next(state) >> 16))
+
+#else
 EWRAM_DATA static u8 sUnknown = 0;
 EWRAM_DATA static u32 sRandCount = 0;
 
-// IWRAM common
-u32 gRngValue;
-u32 gRng2Value;
-
 u16 Random(void)
 {
     gRngValue = ISO_RANDOMIZE1(gRngValue);
@@ -35,15 +115,24 @@ u16 Random2(void)
     return gRng2Value >> 16;
 }
 
+#define LOOP_RANDOM_START
+#define LOOP_RANDOM_END
+
+#define LOOP_RANDOM (Random())
+
+#endif
+
 #define SHUFFLE_IMPL \
     u32 tmp; \
+    LOOP_RANDOM_START; \
     --n; \
     while (n > 1) \
     { \
-        int j = (Random() * (n+1)) >> 16; \
+        int j = (LOOP_RANDOM * (n+1)) >> 16; \
         SWAP(data[n], data[j], tmp); \
         --n; \
-    }
+    } \
+    LOOP_RANDOM_END
 
 void Shuffle8(void *data_, size_t n)
 {
@@ -66,15 +155,19 @@ void Shuffle32(void *data_, size_t n)
 void ShuffleN(void *data, size_t n, size_t size)
 {
     void *tmp = alloca(size);
+    LOOP_RANDOM_START;
     --n;
+
     while (n > 1)
     {
-        int j = (Random() * (n+1)) >> 16;
+        int j = (LOOP_RANDOM * (n+1)) >> 16;
         memcpy(tmp, (u8 *)data + n*size, size); // tmp = data[n];
         memcpy((u8 *)data + n*size, (u8 *)data + j*size, size); // data[n] = data[j];
         memcpy((u8 *)data + j*size, tmp, size); // data[j] = tmp;
         --n;
     }
+
+    LOOP_RANDOM_END;
 }
 
 __attribute__((weak, alias("RandomUniformDefault")))
@@ -96,12 +189,14 @@ u32 RandomUniformDefault(enum RandomTag tag, u32 lo, u32 hi)
 
 u32 RandomUniformExceptDefault(enum RandomTag tag, u32 lo, u32 hi, bool32 (*reject)(u32))
 {
+    LOOP_RANDOM_START;
     while (TRUE)
     {
-        u32 n = RandomUniformDefault(tag, lo, hi);
+        u32 n = lo + (((hi - lo + 1) * LOOP_RANDOM) >> 16);
         if (!reject(n))
             return n;
     }
+    LOOP_RANDOM_END;
 }
 
 u32 RandomWeightedArrayDefault(enum RandomTag tag, u32 sum, u32 n, const u8 *weights)
diff --git a/src/recorded_battle.c b/src/recorded_battle.c
index 4d36ce12b275..bf66e166f63f 100644
--- a/src/recorded_battle.c
+++ b/src/recorded_battle.c
@@ -33,8 +33,8 @@ struct PlayerInfo
 // Save data using TryWriteSpecialSaveSector is allowed to exceed SECTOR_DATA_SIZE (up to the counter field)
 STATIC_ASSERT(sizeof(struct RecordedBattleSave) <= SECTOR_COUNTER_OFFSET, RecordedBattleSaveFreeSpace);
 
-EWRAM_DATA u32 gRecordedBattleRngSeed = 0;
-EWRAM_DATA u32 gBattlePalaceMoveSelectionRngValue = 0;
+EWRAM_DATA rng_value_t gRecordedBattleRngSeed;
+EWRAM_DATA rng_value_t gBattlePalaceMoveSelectionRngValue;
 EWRAM_DATA static u8 sBattleRecords[MAX_BATTLERS_COUNT][BATTLER_RECORD_SIZE] = {0};
 EWRAM_DATA static u16 sBattlerRecordSizes[MAX_BATTLERS_COUNT] = {0};
 EWRAM_DATA static u16 sBattlerPrevRecordSizes[MAX_BATTLERS_COUNT] = {0};

From 99666d42e268af303de1d07dc778f6f29cb711b4 Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Wed, 20 Dec 2023 15:26:33 -0600
Subject: [PATCH 02/18] Empty initialization (fixes agbcc)

---
 include/random.h      | 4 ++++
 src/recorded_battle.c | 4 ++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/include/random.h b/include/random.h
index 0d3cf710698f..264ff0e816e5 100644
--- a/include/random.h
+++ b/include/random.h
@@ -27,6 +27,8 @@ struct Sfc32State {
 
 typedef struct Sfc32State rng_value_t;
 
+#define RNG_VALUE_EMPTY {}
+
 // Calling this function directly is discouraged.
 // Use LocalRandom() instead.
 static inline u32 _SFC32_Next(struct Sfc32State *state)
@@ -60,6 +62,8 @@ void AdvanceRandom(void);
 #else
 typedef u32 rng_value_t;
 
+#define RNG_VALUE_EMPTY 0
+
 //Returns a 16-bit pseudorandom number
 u16 Random(void);
 u16 Random2(void);
diff --git a/src/recorded_battle.c b/src/recorded_battle.c
index bf66e166f63f..1ba62b283712 100644
--- a/src/recorded_battle.c
+++ b/src/recorded_battle.c
@@ -33,8 +33,8 @@ struct PlayerInfo
 // Save data using TryWriteSpecialSaveSector is allowed to exceed SECTOR_DATA_SIZE (up to the counter field)
 STATIC_ASSERT(sizeof(struct RecordedBattleSave) <= SECTOR_COUNTER_OFFSET, RecordedBattleSaveFreeSpace);
 
-EWRAM_DATA rng_value_t gRecordedBattleRngSeed;
-EWRAM_DATA rng_value_t gBattlePalaceMoveSelectionRngValue;
+EWRAM_DATA rng_value_t gRecordedBattleRngSeed = RNG_VALUE_EMPTY;
+EWRAM_DATA rng_value_t gBattlePalaceMoveSelectionRngValue = RNG_VALUE_EMPTY;
 EWRAM_DATA static u8 sBattleRecords[MAX_BATTLERS_COUNT][BATTLER_RECORD_SIZE] = {0};
 EWRAM_DATA static u16 sBattlerRecordSizes[MAX_BATTLERS_COUNT] = {0};
 EWRAM_DATA static u16 sBattlerPrevRecordSizes[MAX_BATTLERS_COUNT] = {0};

From f580028de7cf4c78b043ac3cbb551ff478403fa9 Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Wed, 20 Dec 2023 15:26:54 -0600
Subject: [PATCH 03/18] Make things that are similar but not identical to
 Random32 into Random32 This is probably not all of them

---
 src/debug.c          | 2 +-
 src/load_save.c      | 2 +-
 src/lottery_corner.c | 2 +-
 src/time_events.c    | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/debug.c b/src/debug.c
index 1ed438598be6..c1853af4cf27 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -2144,7 +2144,7 @@ static void DebugAction_Util_Player_Gender(u8 taskId)
 
 static void DebugAction_Util_Player_Id(u8 taskId)
 {
-    u32 trainerId = ((Random() << 16) | Random());
+    u32 trainerId = Random32();
     SetTrainerId(trainerId, gSaveBlock2Ptr->playerTrainerId);
     Debug_DestroyMenu_Full(taskId);
     ScriptContext_Enable();
diff --git a/src/load_save.c b/src/load_save.c
index 4f706180c4e6..d42b71a4a990 100644
--- a/src/load_save.c
+++ b/src/load_save.c
@@ -127,7 +127,7 @@ void MoveSaveBlocks_ResetHeap(void)
     gMain.vblankCallback = vblankCB;
 
     // create a new encryption key
-    encryptionKey = (Random() << 16) + (Random());
+    encryptionKey = Random32();
     ApplyNewEncryptionKeyToAllEncryptedData(encryptionKey);
     gSaveBlock2Ptr->encryptionKey = encryptionKey;
 }
diff --git a/src/lottery_corner.c b/src/lottery_corner.c
index f19e9f7b7b80..b2de9d123c27 100644
--- a/src/lottery_corner.c
+++ b/src/lottery_corner.c
@@ -25,7 +25,7 @@ void ResetLotteryCorner(void)
 {
     u16 rand = Random();
 
-    SetLotteryNumber((Random() << 16) | rand);
+    SetLotteryNumber(Random32());
     VarSet(VAR_POKELOT_PRIZE_ITEM, 0);
 }
 
diff --git a/src/time_events.c b/src/time_events.c
index cec6a44c3415..1c8a12a2375e 100644
--- a/src/time_events.c
+++ b/src/time_events.c
@@ -25,7 +25,7 @@ static void SetMirageRnd(u32 rnd)
 // unused
 void InitMirageRnd(void)
 {
-    SetMirageRnd((Random() << 16) | Random());
+    SetMirageRnd(Random32());
 }
 
 void UpdateMirageRnd(u16 days)

From ca7e5ddcc6b35da42a0678cf43df8b2c9130e30b Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Wed, 20 Dec 2023 19:04:20 -0600
Subject: [PATCH 04/18] Change HQ_RANDOM formatting per Lunos

---
 include/battle.h     |  6 +++---
 include/config.h     |  1 +
 include/random.h     |  6 +-----
 src/battle_main.c    |  2 +-
 src/lottery_corner.c |  2 --
 src/random.c         | 24 ++++++++++--------------
 6 files changed, 16 insertions(+), 25 deletions(-)

diff --git a/include/battle.h b/include/battle.h
index 156b84099789..0d6b69f4493e 100644
--- a/include/battle.h
+++ b/include/battle.h
@@ -15,7 +15,7 @@
 #include "pokeball.h"
 #include "battle_debug.h"
 #include "battle_dynamax.h"
-#include "random.h" // for HQ_RANDOM
+#include "random.h" // for rng_value_t
 
 // Used to exclude moves learned temporarily by Transform or Mimic
 #define MOVE_IS_PERMANENT(battler, moveSlot)                        \
@@ -580,7 +580,7 @@ struct LostItem
     u16 stolen:1;
 };
 
-#if HQ_RANDOM == 1
+#if HQ_RANDOM == TRUE
 struct BattleVideo {
     u32 battleTypeFlags;
     rng_value_t rngSeed;
@@ -659,7 +659,7 @@ struct BattleStruct
     union {
         struct LinkBattlerHeader linkBattlerHeader;
 
-        #if HQ_RANDOM == 0
+        #if HQ_RANDOM == FALSE
         u32 battleVideo[2];
         #else
         struct BattleVideo battleVideo;
diff --git a/include/config.h b/include/config.h
index 8a6e990a5d59..f4be812643dc 100644
--- a/include/config.h
+++ b/include/config.h
@@ -79,5 +79,6 @@
 #define EXPANSION_INTRO              TRUE    // If TRUE, a custom RHH intro will play after the vanilla copyright screen.
 #define POKEDEX_PLUS_HGSS            FALSE   // If TRUE, enables the custom HGSS style Pokedex.
 #define SUMMARY_SCREEN_NATURE_COLORS TRUE    // If TRUE, nature-based stat boosts and reductions will be red and blue in the summary screen.
+#define HQ_RANDOM                    TRUE    // If TRUE, replaces the default RNG with an implementation of SFC32 RNG. May break code that relies on RNG.
 
 #endif // GUARD_CONFIG_H
diff --git a/include/random.h b/include/random.h
index 264ff0e816e5..97e610d4e36b 100644
--- a/include/random.h
+++ b/include/random.h
@@ -6,10 +6,6 @@
 #define ISO_RANDOMIZE1(val)(1103515245 * (val) + 24691)
 #define ISO_RANDOMIZE2(val)(1103515245 * (val) + 12345)
 
-// If 1, use a high-quality PRNG.
-// This may break existing projects.
-#define HQ_RANDOM    1
-
 /* Notes about new functions:
 * If using HQ_RANDOM, you MUST call AdvanceRandom() in VBlank handlers.
 * If you do not, you risk corruption of the RNG state.
@@ -17,7 +13,7 @@
 * Other new functions should be self-explanatory.
 */
 
-#if HQ_RANDOM == 1
+#if HQ_RANDOM == TRUE
 struct Sfc32State {
     u32 a;
     u32 b;
diff --git a/src/battle_main.c b/src/battle_main.c
index f9bdb7595a6c..6fdecdf97764 100644
--- a/src/battle_main.c
+++ b/src/battle_main.c
@@ -1712,7 +1712,7 @@ static void CB2_HandleStartMultiBattle(void)
     case 8:
         if (IsLinkTaskFinished())
         {
-            #if HQ_RANDOM == 1
+            #if HQ_RANDOM == TRUE
             struct BattleVideo *ptr = &gBattleStruct->multiBuffer.battleVideo;
             ptr->battleTypeFlags = gBattleTypeFlags;
             ptr->rngSeed = gRecordedBattleRngSeed;
diff --git a/src/lottery_corner.c b/src/lottery_corner.c
index b2de9d123c27..d06934ca511f 100644
--- a/src/lottery_corner.c
+++ b/src/lottery_corner.c
@@ -23,8 +23,6 @@ static u8 GetMatchingDigits(u16, u16);
 
 void ResetLotteryCorner(void)
 {
-    u16 rand = Random();
-
     SetLotteryNumber(Random32());
     VarSet(VAR_POKELOT_PRIZE_ITEM, 0);
 }
diff --git a/src/random.c b/src/random.c
index 54c61db99eee..79fecdcf241b 100644
--- a/src/random.c
+++ b/src/random.c
@@ -8,9 +8,9 @@
 rng_value_t gRngValue;
 rng_value_t gRng2Value;
 
-#if HQ_RANDOM == 1
-EWRAM_DATA static volatile u8 sUnknown = 11;
-#define RNG_LOCK sUnknown
+#if HQ_RANDOM == TRUE
+EWRAM_DATA static volatile u8 sUnknown = 1;
+#define RNG_LOOP_LOCK sUnknown
 
 
 static void SFC32_Seed(struct Sfc32State *state, u16 seed)
@@ -28,10 +28,8 @@ static void SFC32_Seed(struct Sfc32State *state, u16 seed)
 u32 NAKED Random32(void)
 {
     asm(".thumb\n\
-    push {r4, r5, r6, r7}\n\
-    ldr r7, =sUnknown\n\
+    push {r4, r5, r6}\n\
     mov r6, #11\n\
-    strb r6, [r7]\n\
     ldr r5, =gRngValue\n\
     ldmia r5!, {r1, r2, r3, r4}\n\
     @ e (result) = a + b + d++\n\
@@ -49,9 +47,7 @@ u32 NAKED Random32(void)
     add r3, r3, r0\n\
     sub r5, r5, #16\n\
     stmia r5!, {r1, r2, r3, r4}\n\
-    mov r1, #0\n\
-    strb r1, [r7]\n\
-    pop {r4, r5, r6, r7}\n\
+    pop {r4, r5, r6}\n\
     bx lr\n\
     .ltorg"
     );
@@ -65,7 +61,7 @@ u32 Random2_32(void)
 void SeedRng(u16 seed)
 {
     SFC32_Seed(&gRngValue, seed);
-    RNG_LOCK = 0;
+    RNG_LOOP_LOCK = 0;
 }
 
 void SeedRng2(u16 seed)
@@ -75,15 +71,15 @@ void SeedRng2(u16 seed)
 
 void AdvanceRandom(void)
 {
-    if (RNG_LOCK == 0)
-        _SFC32_Next(&gRngValue);
+    if (RNG_LOOP_LOCK == 0)
+        Random32();
 }
 
 #define LOOP_RANDOM_START \
     struct Sfc32State *const state = &gRngValue; \
-    RNG_LOCK = 11
+    RNG_LOOP_LOCK = 1
 
-#define LOOP_RANDOM_END RNG_LOCK = 0
+#define LOOP_RANDOM_END RNG_LOOP_LOCK = 0
 
 #define LOOP_RANDOM ((u16)(_SFC32_Next(state) >> 16))
 

From 35ae0b35682149316f58767f2a78e3a1c20e243a Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Wed, 20 Dec 2023 19:46:11 -0600
Subject: [PATCH 05/18] Fix test compilation

---
 include/test/battle.h     |  2 +-
 test/test_runner_battle.c | 42 +++++++++++++++++++++++++++++++++------
 2 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/include/test/battle.h b/include/test/battle.h
index c83a61891d8d..f65582220170 100644
--- a/include/test/battle.h
+++ b/include/test/battle.h
@@ -842,7 +842,7 @@ struct moveWithPP {
 void OpenPokemon(u32 sourceLine, u32 side, u32 species);
 void ClosePokemon(u32 sourceLine);
 
-void RNGSeed_(u32 sourceLine, u32 seed);
+void RNGSeed_(u32 sourceLine, rng_value_t seed);
 void AIFlags_(u32 sourceLine, u32 flags);
 void AILogScores(u32 sourceLine);
 void Gender_(u32 sourceLine, u32 gender);
diff --git a/test/test_runner_battle.c b/test/test_runner_battle.c
index ac689676b0fc..e6ff8efee866 100644
--- a/test/test_runner_battle.c
+++ b/test/test_runner_battle.c
@@ -32,8 +32,25 @@
 #define STATE gBattleTestRunnerState
 #define DATA gBattleTestRunnerState->data
 
-#define RNG_SEED_DEFAULT 0x00000000
+#if HQ_RANDOM == TRUE
+#define RNG_SEED_DEFAULT (struct Sfc32State){.a = 0, .b = 0, .c = 0, .ctr = 1}
+static inline bool32 RngSeedNotDefault(const rng_value_t *seed)
+{
+    const struct Sfc32State defaultSeed = RNG_SEED_DEFAULT;
+    return
+        defaultSeed.a != seed->a ||
+        defaultSeed.b != seed->b ||
+        defaultSeed.c != seed->c ||
+        defaultSeed.ctr != seed->ctr;
 
+}
+#else
+#define RNG_SEED_DEFAULT 0x00000000
+static inline bool32 RngSeedNotDefault(const rng_value_t *seed)
+{
+    return *seed != RNG_SEED_DEFAULT;
+}
+#endif
 #undef Q_4_12
 #define Q_4_12(n) (s32)((n) * 4096)
 
@@ -1347,6 +1364,19 @@ static void CB2_BattleTest_NextParameter(void)
     }
 }
 
+static inline rng_value_t MakeRngValue(const u16 seed)
+{
+    #if HQ_RANDOM == TRUE
+        rng_value_t result = {.a = 0, .b = 0, .c = seed, .ctr = 1};
+        for (int i = 0; i < 16; i++)
+        {
+            _SFC32_Next(&result);
+        }
+        return result;
+    #else
+        return ISO_RANDOMIZE1(seed);
+    #endif
+}
 static void CB2_BattleTest_NextTrial(void)
 {
     TearDownBattle();
@@ -1370,7 +1400,7 @@ static void CB2_BattleTest_NextTrial(void)
     {
         PrintTestName();
         gTestRunnerState.result = TEST_RESULT_PASS;
-        DATA.recordedBattle.rngSeed = ISO_RANDOMIZE1(STATE->runTrial);
+        DATA.recordedBattle.rngSeed = MakeRngValue(STATE->runTrial);
         DATA.queuedEvent = 0;
         DATA.lastActionTurn = 0;
         SetVariablesForRecordedBattle(&DATA.recordedBattle);
@@ -1442,16 +1472,16 @@ void Randomly(u32 sourceLine, u32 passes, u32 trials, struct RandomlyContext ctx
     }
     else
     {
-        INVALID_IF(DATA.recordedBattle.rngSeed != RNG_SEED_DEFAULT, "RNG seed already set");
+        INVALID_IF(RngSeedNotDefault(&DATA.recordedBattle.rngSeed), "RNG seed already set");
         STATE->trials = 50;
         STATE->trialRatio = Q_4_12(1) / STATE->trials;
-        DATA.recordedBattle.rngSeed = 0;
+        DATA.recordedBattle.rngSeed = RNG_SEED_DEFAULT;
     }
 }
 
-void RNGSeed_(u32 sourceLine, u32 seed)
+void RNGSeed_(u32 sourceLine, rng_value_t seed)
 {
-    INVALID_IF(DATA.recordedBattle.rngSeed != RNG_SEED_DEFAULT, "RNG seed already set");
+    INVALID_IF(RngSeedNotDefault(&DATA.recordedBattle.rngSeed), "RNG seed already set");
     DATA.recordedBattle.rngSeed = seed;
 }
 

From 25358c4d5a098f577f01414a39b0406d7ce96ffa Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Wed, 20 Dec 2023 20:09:36 -0600
Subject: [PATCH 06/18] Maybe half-fix one test

---
 test/random.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/test/random.c b/test/random.c
index 845f24f102a5..759bb6178411 100644
--- a/test/random.c
+++ b/test/random.c
@@ -227,6 +227,13 @@ TEST("RandomUniform mul-based faster than mod-based (compile-time)")
 
 TEST("RandomUniform mul-based faster than mod-based (run-time)")
 {
+    #if HQ_RANDOM == TRUE
+        const u32 expectedMulSum = 289;
+        const u32 expectedModSum = 249;
+    #else
+        const u32 expectedMulSum = 232;
+        const u32 expectedModSum = 249;
+    #endif
     u32 i;
     struct Benchmark mulBenchmark, modBenchmark;
     u32 mulSum = 0, modSum = 0;

From 82bc6f55321e2ecda5690cb2138a09226323ed6a Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Wed, 20 Dec 2023 20:18:46 -0600
Subject: [PATCH 07/18] More test junk (I develop on a Mac so I can't run tests
 locally.)

---
 test/random.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/test/random.c b/test/random.c
index 759bb6178411..084efd4b8747 100644
--- a/test/random.c
+++ b/test/random.c
@@ -196,6 +196,13 @@ TEST("RandomElement generates a uniform distribution")
 
 TEST("RandomUniform mul-based faster than mod-based (compile-time)")
 {
+    #if HQ_RANDOM == TRUE
+        const u32 expectedMulSum = 6;
+        const u32 expectedModSum = 249;
+    #else
+        const u32 expectedMulSum = 3;
+        const u32 expectedModSum = 249;
+    #endif
     struct Benchmark mulBenchmark, modBenchmark;
     u32 mulSum = 0, modSum = 0;
 
@@ -221,8 +228,8 @@ TEST("RandomUniform mul-based faster than mod-based (compile-time)")
     // These numbers are different because multiplication and modulus
     // have subtly different biases (so subtle that it's irrelevant for
     // our purposes).
-    EXPECT_EQ(mulSum, 3);
-    EXPECT_EQ(modSum, 4);
+    EXPECT_EQ(mulSum, expectedMulSum);
+    EXPECT_EQ(modSum, expectedModSum);
 }
 
 TEST("RandomUniform mul-based faster than mod-based (run-time)")
@@ -253,6 +260,6 @@ TEST("RandomUniform mul-based faster than mod-based (run-time)")
     EXPECT_FASTER(mulBenchmark, modBenchmark);
 
     // Reference mulSum/modSum to prevent optimization.
-    EXPECT_EQ(mulSum, 232);
-    EXPECT_EQ(modSum, 249);
+    EXPECT_EQ(mulSum, expectedMulSum);
+    EXPECT_EQ(modSum, expectedModSum);
 }

From 50b70f217b29bff8fb5e4afc1c40dab1e68e91fa Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Wed, 20 Dec 2023 22:23:21 -0600
Subject: [PATCH 08/18] Maybe fix complaining about RNG seed not being set

---
 test/random.c             | 6 +++---
 test/test_runner_battle.c | 9 ++-------
 2 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/test/random.c b/test/random.c
index 084efd4b8747..48860b5ff2d1 100644
--- a/test/random.c
+++ b/test/random.c
@@ -198,10 +198,10 @@ TEST("RandomUniform mul-based faster than mod-based (compile-time)")
 {
     #if HQ_RANDOM == TRUE
         const u32 expectedMulSum = 6;
-        const u32 expectedModSum = 249;
+        const u32 expectedModSum = 4;
     #else
         const u32 expectedMulSum = 3;
-        const u32 expectedModSum = 249;
+        const u32 expectedModSum = 4;
     #endif
     struct Benchmark mulBenchmark, modBenchmark;
     u32 mulSum = 0, modSum = 0;
@@ -239,7 +239,7 @@ TEST("RandomUniform mul-based faster than mod-based (run-time)")
         const u32 expectedModSum = 249;
     #else
         const u32 expectedMulSum = 232;
-        const u32 expectedModSum = 249;
+        const u32 expectedModSum = 205;
     #endif
     u32 i;
     struct Benchmark mulBenchmark, modBenchmark;
diff --git a/test/test_runner_battle.c b/test/test_runner_battle.c
index e6ff8efee866..c7c3eac5b463 100644
--- a/test/test_runner_battle.c
+++ b/test/test_runner_battle.c
@@ -33,15 +33,10 @@
 #define DATA gBattleTestRunnerState->data
 
 #if HQ_RANDOM == TRUE
-#define RNG_SEED_DEFAULT (struct Sfc32State){.a = 0, .b = 0, .c = 0, .ctr = 1}
+#define RNG_SEED_DEFAULT (struct Sfc32State){.a = 0, .b = 0, .c = 0, .ctr = 0}
 static inline bool32 RngSeedNotDefault(const rng_value_t *seed)
 {
-    const struct Sfc32State defaultSeed = RNG_SEED_DEFAULT;
-    return
-        defaultSeed.a != seed->a ||
-        defaultSeed.b != seed->b ||
-        defaultSeed.c != seed->c ||
-        defaultSeed.ctr != seed->ctr;
+    return (seed->a | seed->b | seed->c | seed->ctr) != 0;
 
 }
 #else

From 9bac69d62d0d90580f2c1c2d4bb7567737eb143b Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Wed, 20 Dec 2023 22:45:55 -0600
Subject: [PATCH 09/18] Hopefully make the last tests pass This makes the
 shuffle error a bit more tolerant

---
 test/random.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/test/random.c b/test/random.c
index 48860b5ff2d1..0649ba9a7bbf 100644
--- a/test/random.c
+++ b/test/random.c
@@ -17,7 +17,7 @@
     error = 0; \
     for (i = 0; i < ARRAY_COUNT(indexSum); i++) \
         error += abs(3584 - indexSum[i]); \
-    EXPECT_LT(error, (int)(28672 * 0.025));
+    EXPECT_LT(error, (int)(28672 * 0.03));
 
 TEST("Shuffle randomizes the array [Shuffle8]")
 {
@@ -236,10 +236,10 @@ TEST("RandomUniform mul-based faster than mod-based (run-time)")
 {
     #if HQ_RANDOM == TRUE
         const u32 expectedMulSum = 289;
-        const u32 expectedModSum = 249;
+        const u32 expectedModSum = 205;
     #else
         const u32 expectedMulSum = 232;
-        const u32 expectedModSum = 205;
+        const u32 expectedModSum = 249;
     #endif
     u32 i;
     struct Benchmark mulBenchmark, modBenchmark;

From 9b6439a9a4a241b46db2875f8d0012bcbfc34890 Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Thu, 21 Dec 2023 09:59:55 -0600
Subject: [PATCH 10/18] Review updates and separate streams for Random2

---
 include/config.h |  2 +-
 include/random.h | 11 ++++++++---
 src/random.c     | 41 +++++++++++++++++++++++++++--------------
 3 files changed, 36 insertions(+), 18 deletions(-)

diff --git a/include/config.h b/include/config.h
index f4be812643dc..a61e8de56c36 100644
--- a/include/config.h
+++ b/include/config.h
@@ -79,6 +79,6 @@
 #define EXPANSION_INTRO              TRUE    // If TRUE, a custom RHH intro will play after the vanilla copyright screen.
 #define POKEDEX_PLUS_HGSS            FALSE   // If TRUE, enables the custom HGSS style Pokedex.
 #define SUMMARY_SCREEN_NATURE_COLORS TRUE    // If TRUE, nature-based stat boosts and reductions will be red and blue in the summary screen.
-#define HQ_RANDOM                    TRUE    // If TRUE, replaces the default RNG with an implementation of SFC32 RNG. May break code that relies on RNG.
+#define HQ_RANDOM                    FALSE   // If TRUE, replaces the default RNG with an implementation of SFC32 RNG. May break code that relies on RNG.
 
 #endif // GUARD_CONFIG_H
diff --git a/include/random.h b/include/random.h
index 97e610d4e36b..e8f0038f3e71 100644
--- a/include/random.h
+++ b/include/random.h
@@ -7,9 +7,14 @@
 #define ISO_RANDOMIZE2(val)(1103515245 * (val) + 12345)
 
 /* Notes about new functions:
-* If using HQ_RANDOM, you MUST call AdvanceRandom() in VBlank handlers.
-* If you do not, you risk corruption of the RNG state.
-* LocalRandom(*val) adapts to either choice of RNG implementation.
+*
+* If using HQ_RANDOM, you cannot call Random() in interrupt handlers safely.
+* AdvanceRandom() is provided to handle burning numbers in the VBlank handler
+* if you choose to do that, and can be used regardless of HQ_RANDOM setting.
+*
+* LocalRandom(*val) allows you to have local random states that are the same
+* type as the global states regardless of HQ_RANDOM setting.
+*
 * Other new functions should be self-explanatory.
 */
 
diff --git a/src/random.c b/src/random.c
index 79fecdcf241b..0aa6a4459f22 100644
--- a/src/random.c
+++ b/src/random.c
@@ -9,19 +9,33 @@ rng_value_t gRngValue;
 rng_value_t gRng2Value;
 
 #if HQ_RANDOM == TRUE
-EWRAM_DATA static volatile u8 sUnknown = 1;
-#define RNG_LOOP_LOCK sUnknown
+EWRAM_DATA static volatile bool8 sRngLoopUnlocked;
 
+// Do not change STREAM1 without changing Random32().
+#define STREAM1 1
+#define STREAM2 29
 
-static void SFC32_Seed(struct Sfc32State *state, u16 seed)
+// A variant of SFC32 that lets you change the stream.
+// stream cannot be even, but any other (8-bit) value should be OK.
+static inline u32 _SFC32_Next_Stream(struct Sfc32State *state, const u8 stream)
+{
+    const u32 result = state->a + state->b + state->ctr;
+    state->ctr += stream;
+    state->a = state->b ^ (state->b >> 9);
+    state->b = state->c * 9;
+    state->c = result + ((state->c << 21) | (state->c >> 11));
+    return result;
+}
+
+static void SFC32_Seed(struct Sfc32State *state, u16 seed, u8 stream)
 {
     u32 i;
     state->a = state->b = 0;
     state->c = seed;
-    state->ctr = 1;
+    state->ctr = stream;
     for(i = 0; i < 16; i++)
     {
-        _SFC32_Next(state);
+        _SFC32_Next_Stream(state, stream);
     }
 }
 
@@ -35,6 +49,7 @@ u32 NAKED Random32(void)
     @ e (result) = a + b + d++\n\
     add r1, r1, r2\n\
     add r0, r1, r4\n\
+    @the argument is the same as STREAM1\n\
     add r4, r4, #1\n\
     @ a = b ^ (b >> 9)\n\
     lsr r1, r2, #9\n\
@@ -55,36 +70,35 @@ u32 NAKED Random32(void)
 
 u32 Random2_32(void)
 {
-    return _SFC32_Next(&gRng2Value);
+    return _SFC32_Next_Stream(&gRng2Value, STREAM2);
 }
 
 void SeedRng(u16 seed)
 {
-    SFC32_Seed(&gRngValue, seed);
-    RNG_LOOP_LOCK = 0;
+    SFC32_Seed(&gRngValue, seed, STREAM1);
+    sRngLoopUnlocked = TRUE;
 }
 
 void SeedRng2(u16 seed)
 {
-    SFC32_Seed(&gRng2Value, seed);
+    SFC32_Seed(&gRng2Value, seed, STREAM2);
 }
 
 void AdvanceRandom(void)
 {
-    if (RNG_LOOP_LOCK == 0)
+    if (sRngLoopUnlocked == TRUE)
         Random32();
 }
 
 #define LOOP_RANDOM_START \
     struct Sfc32State *const state = &gRngValue; \
-    RNG_LOOP_LOCK = 1
+    sRngLoopUnlocked = FALSE;
 
-#define LOOP_RANDOM_END RNG_LOOP_LOCK = 0
+#define LOOP_RANDOM_END sRngLoopUnlocked = TRUE;
 
 #define LOOP_RANDOM ((u16)(_SFC32_Next(state) >> 16))
 
 #else
-EWRAM_DATA static u8 sUnknown = 0;
 EWRAM_DATA static u32 sRandCount = 0;
 
 u16 Random(void)
@@ -97,7 +111,6 @@ u16 Random(void)
 void SeedRng(u16 seed)
 {
     gRngValue = seed;
-    sUnknown = 0;
 }
 
 void SeedRng2(u16 seed)

From f5a27654e7dc90da7b1359f7b8f77cbfb00253ea Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Thu, 21 Dec 2023 10:04:05 -0600
Subject: [PATCH 11/18] Change HQ_RANDOM back to TRUE for testing

---
 include/config.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/config.h b/include/config.h
index a61e8de56c36..f4be812643dc 100644
--- a/include/config.h
+++ b/include/config.h
@@ -79,6 +79,6 @@
 #define EXPANSION_INTRO              TRUE    // If TRUE, a custom RHH intro will play after the vanilla copyright screen.
 #define POKEDEX_PLUS_HGSS            FALSE   // If TRUE, enables the custom HGSS style Pokedex.
 #define SUMMARY_SCREEN_NATURE_COLORS TRUE    // If TRUE, nature-based stat boosts and reductions will be red and blue in the summary screen.
-#define HQ_RANDOM                    FALSE   // If TRUE, replaces the default RNG with an implementation of SFC32 RNG. May break code that relies on RNG.
+#define HQ_RANDOM                    TRUE    // If TRUE, replaces the default RNG with an implementation of SFC32 RNG. May break code that relies on RNG.
 
 #endif // GUARD_CONFIG_H

From 16614b13843439fd2b98805f35ea525536b919ae Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Thu, 21 Dec 2023 11:53:41 -0600
Subject: [PATCH 12/18] agbcc doesn't support struct literals

---
 test/test_runner_battle.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/test_runner_battle.c b/test/test_runner_battle.c
index c7c3eac5b463..c17cf85906bd 100644
--- a/test/test_runner_battle.c
+++ b/test/test_runner_battle.c
@@ -33,7 +33,7 @@
 #define DATA gBattleTestRunnerState->data
 
 #if HQ_RANDOM == TRUE
-#define RNG_SEED_DEFAULT (struct Sfc32State){.a = 0, .b = 0, .c = 0, .ctr = 0}
+#define RNG_SEED_DEFAULT {0, 0, 0, 0}
 static inline bool32 RngSeedNotDefault(const rng_value_t *seed)
 {
     return (seed->a | seed->b | seed->c | seed->ctr) != 0;

From ecfa3d9975c428a854c19790365f9a87e268d5d3 Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Thu, 21 Dec 2023 12:45:14 -0600
Subject: [PATCH 13/18] Fix tests that I broke on agbcc (There are other broken
 tests on agbcc but those are out of scope for my changes)

---
 test/test_runner_battle.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/test/test_runner_battle.c b/test/test_runner_battle.c
index c17cf85906bd..dd7813d2f093 100644
--- a/test/test_runner_battle.c
+++ b/test/test_runner_battle.c
@@ -268,11 +268,12 @@ static void BattleTest_Run(void *data)
     s32 i;
     u32 requiredPlayerPartySize;
     u32 requiredOpponentPartySize;
+    const rng_value_t defaultSeed = RNG_SEED_DEFAULT;
     const struct BattleTest *test = data;
 
     memset(&DATA, 0, sizeof(DATA));
 
-    DATA.recordedBattle.rngSeed = RNG_SEED_DEFAULT;
+    DATA.recordedBattle.rngSeed = defaultSeed;
     DATA.recordedBattle.textSpeed = OPTIONS_TEXT_SPEED_FAST;
     // Set battle flags and opponent ids.
     switch (test->type)
@@ -1362,8 +1363,9 @@ static void CB2_BattleTest_NextParameter(void)
 static inline rng_value_t MakeRngValue(const u16 seed)
 {
     #if HQ_RANDOM == TRUE
-        rng_value_t result = {.a = 0, .b = 0, .c = seed, .ctr = 1};
-        for (int i = 0; i < 16; i++)
+        int i;
+        rng_value_t result = {0, 0, seed, 1};
+        for (i = 0; i < 16; i++)
         {
             _SFC32_Next(&result);
         }
@@ -1467,10 +1469,11 @@ void Randomly(u32 sourceLine, u32 passes, u32 trials, struct RandomlyContext ctx
     }
     else
     {
+        const rng_value_t defaultSeed = RNG_SEED_DEFAULT;
         INVALID_IF(RngSeedNotDefault(&DATA.recordedBattle.rngSeed), "RNG seed already set");
         STATE->trials = 50;
         STATE->trialRatio = Q_4_12(1) / STATE->trials;
-        DATA.recordedBattle.rngSeed = RNG_SEED_DEFAULT;
+        DATA.recordedBattle.rngSeed = defaultSeed;
     }
 }
 

From 575e512004b5007a75ba15cdd3de41409d546935 Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Thu, 21 Dec 2023 15:44:59 -0600
Subject: [PATCH 14/18] New

---
 test/random.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/test/random.c b/test/random.c
index 0649ba9a7bbf..7e1e085e9b2e 100644
--- a/test/random.c
+++ b/test/random.c
@@ -263,3 +263,27 @@ TEST("RandomUniform mul-based faster than mod-based (run-time)")
     EXPECT_EQ(mulSum, expectedMulSum);
     EXPECT_EQ(modSum, expectedModSum);
 }
+
+#if HQ_RANDOM == TRUE
+TEST("Thumb and C SFC32 implementations produce the same results")
+{
+    u32 thumbSum;
+    u32 cSum;
+    int i;
+    rng_value_t localState;
+
+    thumbSum = 0;
+    cSum = 0;
+
+    SeedRng(0);
+    localState = gRngValue;
+
+    for(i = 0; i < 32; i++)
+    {
+        thumbSum += Random();
+        cSum += _SFC32_Next(&localState);
+    }
+
+    EXPECT_EQ(thumbSum, cSum);
+}
+#endif
\ No newline at end of file

From b68e897436d684ec207d963669afafad01bac382 Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Thu, 21 Dec 2023 16:05:18 -0600
Subject: [PATCH 15/18] possibly fix thumb sfc?

---
 src/random.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/random.c b/src/random.c
index 0aa6a4459f22..709584b5ec96 100644
--- a/src/random.c
+++ b/src/random.c
@@ -39,11 +39,13 @@ static void SFC32_Seed(struct Sfc32State *state, u16 seed, u8 stream)
     }
 }
 
+// As the most frequently called RNG function, this is written in assembly
+// for speed. It is functionally equivalent to _SFC32_Next(&gRngValue)
 u32 NAKED Random32(void)
 {
     asm(".thumb\n\
     push {r4, r5, r6}\n\
-    mov r6, #11\n\
+    mov r6, #21\n\
     ldr r5, =gRngValue\n\
     ldmia r5!, {r1, r2, r3, r4}\n\
     @ e (result) = a + b + d++\n\
@@ -57,7 +59,7 @@ u32 NAKED Random32(void)
     @ b = c + (c << 3) [c * 9]\n\
     lsl r2, r3, #3\n\
     add r2, r2, r3\n\
-    @ c = rol(c, 21) + e\n\
+    @ c = ror(c, 21) + e\n\
     ror r3, r3, r6\n\
     add r3, r3, r0\n\
     sub r5, r5, #16\n\

From 7075780848ef65444871b0552c3efaf467505136 Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Thu, 21 Dec 2023 16:11:11 -0600
Subject: [PATCH 16/18] Revert "possibly fix thumb sfc?" OOPS i did the test
 wrong. Sad!

This reverts commit b68e897436d684ec207d963669afafad01bac382.
---
 src/random.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/random.c b/src/random.c
index 709584b5ec96..0aa6a4459f22 100644
--- a/src/random.c
+++ b/src/random.c
@@ -39,13 +39,11 @@ static void SFC32_Seed(struct Sfc32State *state, u16 seed, u8 stream)
     }
 }
 
-// As the most frequently called RNG function, this is written in assembly
-// for speed. It is functionally equivalent to _SFC32_Next(&gRngValue)
 u32 NAKED Random32(void)
 {
     asm(".thumb\n\
     push {r4, r5, r6}\n\
-    mov r6, #21\n\
+    mov r6, #11\n\
     ldr r5, =gRngValue\n\
     ldmia r5!, {r1, r2, r3, r4}\n\
     @ e (result) = a + b + d++\n\
@@ -59,7 +57,7 @@ u32 NAKED Random32(void)
     @ b = c + (c << 3) [c * 9]\n\
     lsl r2, r3, #3\n\
     add r2, r2, r3\n\
-    @ c = ror(c, 21) + e\n\
+    @ c = rol(c, 21) + e\n\
     ror r3, r3, r6\n\
     add r3, r3, r0\n\
     sub r5, r5, #16\n\

From 79a7e993211ab0ae00b29e6a1a4625a1bf677b9f Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Thu, 21 Dec 2023 16:11:57 -0600
Subject: [PATCH 17/18] Fix test

---
 test/random.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/random.c b/test/random.c
index 7e1e085e9b2e..0232ff154731 100644
--- a/test/random.c
+++ b/test/random.c
@@ -280,7 +280,7 @@ TEST("Thumb and C SFC32 implementations produce the same results")
 
     for(i = 0; i < 32; i++)
     {
-        thumbSum += Random();
+        thumbSum += Random32();
         cSum += _SFC32_Next(&localState);
     }
 

From a539f3f7e481d3ddb01f380469f1285f78c23c3c Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Fri, 22 Dec 2023 11:06:03 -0600
Subject: [PATCH 18/18] Review changes and others

---
 include/random.h                      | 11 ++++++++---
 include/recorded_battle.h             |  2 +-
 src/battle_controller_link_opponent.c |  2 +-
 src/battle_controller_link_partner.c  |  2 +-
 src/random.c                          | 16 +++++++++++-----
 5 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/include/random.h b/include/random.h
index e8f0038f3e71..a13b28674f7a 100644
--- a/include/random.h
+++ b/include/random.h
@@ -6,16 +6,21 @@
 #define ISO_RANDOMIZE1(val)(1103515245 * (val) + 24691)
 #define ISO_RANDOMIZE2(val)(1103515245 * (val) + 12345)
 
-/* Notes about new functions:
+/* Some functions have been added to support HQ_RANDOM.
 *
 * If using HQ_RANDOM, you cannot call Random() in interrupt handlers safely.
 * AdvanceRandom() is provided to handle burning numbers in the VBlank handler
 * if you choose to do that, and can be used regardless of HQ_RANDOM setting.
+* If you need to use random numbers in the VBlank handler, a local state
+* should be used instead.
 *
 * LocalRandom(*val) allows you to have local random states that are the same
-* type as the global states regardless of HQ_RANDOM setting.
+* type as the global states regardless of HQ_RANDOM setting, which is useful
+* if you want to be able to set them from or assign them to gRngValue.
 *
-* Other new functions should be self-explanatory.
+* Random2_32() was added to HQ_RANDOM because the output of the generator is
+* always 32 bits and Random()/Random2() are just wrappers in that mode. It is
+* also available in non-HQ mode for consistency.
 */
 
 #if HQ_RANDOM == TRUE
diff --git a/include/recorded_battle.h b/include/recorded_battle.h
index 5d3f47d14014..c64a665b74fe 100644
--- a/include/recorded_battle.h
+++ b/include/recorded_battle.h
@@ -2,7 +2,7 @@
 #define GUARD_RECORDED_BATTLE_H
 
 #include "constants/battle.h"
-#include "random.h" // for rng_value_t
+#include "random.h"
 
 #define BATTLER_RECORD_SIZE 664
 
diff --git a/src/battle_controller_link_opponent.c b/src/battle_controller_link_opponent.c
index 03080e501625..c9197bc5dfd3 100644
--- a/src/battle_controller_link_opponent.c
+++ b/src/battle_controller_link_opponent.c
@@ -28,7 +28,7 @@
 #include "constants/songs.h"
 #include "constants/trainers.h"
 #include "recorded_battle.h"
-#include "random.h" // for rng_value_t
+#include "random.h"
 
 static void LinkOpponentHandleLoadMonSprite(u32 battler);
 static void LinkOpponentHandleSwitchInAnim(u32 battler);
diff --git a/src/battle_controller_link_partner.c b/src/battle_controller_link_partner.c
index 93fdfd7fef18..e5fb49bebf65 100644
--- a/src/battle_controller_link_partner.c
+++ b/src/battle_controller_link_partner.c
@@ -28,7 +28,7 @@
 #include "constants/songs.h"
 #include "constants/trainers.h"
 #include "recorded_battle.h"
-#include "random.h" // for rng_value_t
+#include "random.h"
 
 static void LinkPartnerHandleLoadMonSprite(u32 battler);
 static void LinkPartnerHandleSwitchInAnim(u32 battler);
diff --git a/src/random.c b/src/random.c
index 0aa6a4459f22..db82334aa930 100644
--- a/src/random.c
+++ b/src/random.c
@@ -9,14 +9,15 @@ rng_value_t gRngValue;
 rng_value_t gRng2Value;
 
 #if HQ_RANDOM == TRUE
+
 EWRAM_DATA static volatile bool8 sRngLoopUnlocked;
 
-// Do not change STREAM1 without changing Random32().
+// Streams allow generators seeded the same to have separate outputs.
 #define STREAM1 1
 #define STREAM2 29
 
 // A variant of SFC32 that lets you change the stream.
-// stream cannot be even, but any other (8-bit) value should be OK.
+// stream can be any odd number.
 static inline u32 _SFC32_Next_Stream(struct Sfc32State *state, const u8 stream)
 {
     const u32 result = state->a + state->b + state->ctr;
@@ -39,6 +40,8 @@ static void SFC32_Seed(struct Sfc32State *state, u16 seed, u8 stream)
     }
 }
 
+/*This ASM implementation uses some shortcuts and is generally faster on the GBA.
+* It's not necessarily faster if inlined, or on other platforms. */
 u32 NAKED Random32(void)
 {
     asm(".thumb\n\
@@ -49,8 +52,7 @@ u32 NAKED Random32(void)
     @ e (result) = a + b + d++\n\
     add r1, r1, r2\n\
     add r0, r1, r4\n\
-    @the argument is the same as STREAM1\n\
-    add r4, r4, #1\n\
+    add r4, r4, #" STR(STREAM1) "\n\
     @ a = b ^ (b >> 9)\n\
     lsr r1, r2, #9\n\
     eor r1, r1, r2\n\
@@ -75,7 +77,11 @@ u32 Random2_32(void)
 
 void SeedRng(u16 seed)
 {
-    SFC32_Seed(&gRngValue, seed, STREAM1);
+    struct Sfc32State state;
+    SFC32_Seed(&state, seed, STREAM1);
+
+    sRngLoopUnlocked = FALSE;
+    gRngValue = state;
     sRngLoopUnlocked = TRUE;
 }