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AndersamaAndersama
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Use Melissa E. O'Neill's pcg for rng and Lemire's unbiased bounded rand
 Mersenne Twister's state size is huge (kb's of state), instead we'll swap with a pcg. The pcg's state is n bits and has a equidistributed 2^(n/2) period (plenty for a quick rng). To replicate std::distribution we use lemire's unbiased bounded random method. Adjust the state size as desired between 32 and 128 bits.
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12 files changed

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‎src/CMakeLists.txt‎

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Original file line numberDiff line numberDiff line change
@@ -473,6 +473,8 @@ list(APPEND SOURCE_FILES
473473
components/stopwatch/StopWatchController.cpp
474474
components/alarm/AlarmController.cpp
475475
components/fs/FS.cpp
476+
components/rng/PCG.cpp
477+
476478
drivers/Cst816s.cpp
477479
FreeRTOS/port.c
478480
FreeRTOS/port_cmsis_systick.c
@@ -662,6 +664,7 @@ set(INCLUDE_FILES
662664
components/timer/Timer.h
663665
components/stopwatch/StopWatchController.h
664666
components/alarm/AlarmController.h
667+
components/rng/PCG.h
665668
drivers/Cst816s.h
666669
FreeRTOS/portmacro.h
667670
FreeRTOS/portmacro_cmsis.h

‎src/components/rng/PCG.cpp‎

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@@ -0,0 +1,86 @@
1+
#include "components/rng/PCG.h"
2+
3+
Pinetime::Controllers::RNG::State Pinetime::Controllers::RNG::Seed(Pinetime::Controllers::RNG::rng_uint s,
4+
Pinetime::Controllers::RNG::rng_uint i) {
5+
rng.state = 0u;
6+
rng.inc = i | 1u;
7+
Generate();
8+
rng.state += s;
9+
Generate();
10+
return rng;
11+
}
12+
13+
Pinetime::Controllers::RNG::State Pinetime::Controllers::RNG::Seed() {
14+
using namespace Pinetime::Controllers;
15+
Pinetime::Controllers::RNG::State new_rng;
16+
new_rng.state = (RNG::rng_uint) Generate() << (sizeof(new_rng.state) * 4) ^ (RNG::rng_uint) Generate();
17+
new_rng.inc = (RNG::rng_uint) Generate() << (sizeof(new_rng.inc) * 4) ^ (RNG::rng_uint) Generate();
18+
return new_rng;
19+
}
20+
21+
// *Really* minimal PCG32 code / (c) 2014 M.E. O'Neill / pcg-random.org
22+
// Licensed under Apache License 2.0 (NO WARRANTY, etc. see website)
23+
// Website: https://www.pcg-random.org/download.html
24+
// See: https://www.apache.org/licenses/GPL-compatibility.html
25+
/*
26+
uint64_t oldstate = rng.state;
27+
// Advance internal state
28+
rng.state = oldstate * 6364136223846793005ULL + (rng.inc | 1);
29+
// Calculate output function (XSH RR), uses old state for max ILP
30+
uint32_t xorshifted = ((oldstate >> 18u) ^ oldstate) >> 27u;
31+
uint32_t rot = oldstate >> 59u;
32+
return (xorshifted >> rot) | (xorshifted << ((-rot) & 31));
33+
*/
34+
Pinetime::Controllers::RNG::rng_out Pinetime::Controllers::RNG::Generate() {
35+
using namespace Pinetime::Controllers;
36+
// See magic numbers in https://github.com/imneme/pcg-cpp/blob/master/include/pcg_random.hpp
37+
constexpr uint32_t tbits = sizeof(rng.state) * 8;
38+
constexpr uint32_t sbits = sizeof(rng) * 8;
39+
constexpr uint32_t obits = sizeof(RNG::rng_out) * 8;
40+
41+
constexpr rng_uint multiplier = tbits >= 64 ? 1442695040888963407ULL : tbits >= 32 ? 747796405U : tbits >= 16 ? 12829U : 141u;
42+
43+
constexpr uint32_t opbits = sbits - 5 >= 64 ? 5u : // 128 bits -> 5
44+
sbits - 4 >= 32 ? 4u
45+
: // 64 bits -> 4
46+
sbits - 3 >= 16 ? 3u
47+
: // 32 bits -> 3
48+
sbits - 2 >= 8 ? 2u
49+
: // 16 bits -> 2
50+
sbits - 1 >= 1 ? 1u
51+
: // 8 bits -> 1
52+
0u;
53+
54+
auto oldstate = rng.state;
55+
rng.state = oldstate * multiplier + (rng.inc | 1);
56+
// 64 bits of state, 32 output (64 - 5 = 59, 32 - 5 = 27 and floor((5+32)/2) = 18)
57+
// 2^5 = 32*
58+
// output = rotate<s3,s2,s1>(state ^ (state >> s1)) >> s2, state >> s3)
59+
// 32 bits of state, 16 output (32 - 4 = 28, 16 - 4 = 12, and floor((4 + 16)/2) = 10)
60+
// 2^4 = 16*
61+
constexpr uint32_t s3 = tbits - opbits;
62+
constexpr uint32_t s2 = obits - opbits;
63+
constexpr uint32_t s1 = (obits + 5) / 2;
64+
65+
constexpr RNG::rng_out mask = (1 << opbits) - 1;
66+
RNG::rng_out xorshifted = ((oldstate >> s1) ^ oldstate) >> s2;
67+
rng_out rot = oldstate >> s3;
68+
// rotate
69+
return (xorshifted >> rot) | (xorshifted << ((-rot) & mask));
70+
};
71+
72+
// Lemire's Method (slight rewrite) [0, range)
73+
Pinetime::Controllers::RNG::rng_out Pinetime::Controllers::RNG::GenerateBounded(Pinetime::Controllers::RNG::rng_out range) {
74+
using namespace Pinetime::Controllers;
75+
rng_uint m;
76+
RNG::rng_out t = (-range) % range;
77+
RNG::rng_out l;
78+
79+
do {
80+
RNG::rng_out x = Generate();
81+
m = RNG::rng_uint(x) * RNG::rng_uint(range);
82+
l = RNG::rng_out(m);
83+
} while (l < t);
84+
85+
return m >> (sizeof(RNG::rng_out) * 8);
86+
};

‎src/components/rng/PCG.h‎

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@@ -0,0 +1,43 @@
1+
#pragma once
2+
#include <cstdint>
3+
#include <FreeRTOS.h>
4+
#include <timers.h>
5+
#include "components/motion/MotionController.h"
6+
7+
namespace Pinetime {
8+
namespace Controllers {
9+
struct RNG {
10+
using rng_uint = uint32_t;
11+
using rng_uint2 = uint64_t;
12+
using rng_out = uint16_t;
13+
14+
struct pcg_random_t {
15+
rng_uint state = {};
16+
rng_uint inc = {};
17+
};
18+
19+
using State = pcg_random_t;
20+
State rng = {};
21+
22+
State Seed(rng_uint s, rng_uint i);
23+
// Generate another RNG struct with data generated via this one
24+
State Seed();
25+
// Produces an unsigned result within the full range of the data type
26+
rng_out Generate();
27+
// Produces an unsigned result within [0, range)
28+
rng_out GenerateBounded(rng_out range);
29+
30+
RNG() : rng() {};
31+
32+
RNG& operator=(const State& pcg_state) {
33+
rng = pcg_state;
34+
};
35+
36+
RNG(State pcg_state) {
37+
rng = pcg_state;
38+
};
39+
40+
~RNG() = default;
41+
};
42+
}
43+
}

‎src/displayapp/Controllers.h‎

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@@ -26,6 +26,7 @@ namespace Pinetime {
2626
class Timer;
2727
class MusicService;
2828
class NavigationService;
29+
class RNG;
2930
}
3031

3132
namespace System {
@@ -53,6 +54,7 @@ namespace Pinetime {
5354
Pinetime::Components::LittleVgl& lvgl;
5455
Pinetime::Controllers::MusicService* musicService;
5556
Pinetime::Controllers::NavigationService* navigationService;
57+
Pinetime::Controllers::RNG* prngController;
5658
};
5759
}
5860
}

‎src/displayapp/DisplayApp.cpp‎

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@@ -717,6 +717,7 @@ void DisplayApp::PushMessageToSystemTask(Pinetime::System::Messages message) {
717717
void DisplayApp::Register(Pinetime::System::SystemTask* systemTask) {
718718
this->systemTask = systemTask;
719719
this->controllers.systemTask = systemTask;
720+
this->controllers.prngController = &(systemTask->prngController);
720721
}
721722

722723
void DisplayApp::Register(Pinetime::Controllers::SimpleWeatherService* weatherService) {

‎src/displayapp/screens/Dice.cpp‎

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Original file line numberDiff line numberDiff line change
@@ -41,13 +41,10 @@ namespace {
4141

4242
Dice::Dice(Controllers::MotionController& motionController,
4343
Controllers::MotorController& motorController,
44-
Controllers::Settings& settingsController)
44+
Controllers::Settings& settingsController,
45+
Controllers::RNG& prngController)
4546
: motorController {motorController}, motionController {motionController}, settingsController {settingsController} {
46-
std::seed_seq sseq {static_cast<uint32_t>(xTaskGetTickCount()),
47-
static_cast<uint32_t>(motionController.X()),
48-
static_cast<uint32_t>(motionController.Y()),
49-
static_cast<uint32_t>(motionController.Z())};
50-
gen.seed(sseq);
47+
rng = prngController.Seed();
5148

5249
lv_obj_t* nCounterLabel = MakeLabel(&jetbrains_mono_bold_20,
5350
LV_COLOR_WHITE,
@@ -79,8 +76,7 @@ Dice::Dice(Controllers::MotionController& motionController,
7976
lv_obj_align(dCounter.GetObject(), dCounterLabel, LV_ALIGN_OUT_BOTTOM_MID, 0, 10);
8077
dCounter.SetValue(6);
8178

82-
std::uniform_int_distribution<> distrib(0, resultColors.size() - 1);
83-
currentColorIndex = distrib(gen);
79+
currentColorIndex = rng.GenerateBounded(resultColors.size());
8480

8581
resultTotalLabel = MakeLabel(&jetbrains_mono_42,
8682
resultColors[currentColorIndex],
@@ -157,12 +153,10 @@ void Dice::Refresh() {
157153
void Dice::Roll() {
158154
uint8_t resultIndividual;
159155
uint16_t resultTotal = 0;
160-
std::uniform_int_distribution<> distrib(1, dCounter.GetValue());
161-
162156
lv_label_set_text(resultIndividualLabel, "");
163157

164158
if (nCounter.GetValue() == 1) {
165-
resultTotal = distrib(gen);
159+
resultTotal = rng.GenerateBounded(dCounter.GetValue()) + 1;
166160
if (dCounter.GetValue() == 2) {
167161
switch (resultTotal) {
168162
case 1:
@@ -175,7 +169,7 @@ void Dice::Roll() {
175169
}
176170
} else {
177171
for (uint8_t i = 0; i < nCounter.GetValue(); i++) {
178-
resultIndividual = distrib(gen);
172+
resultIndividual = rng.GenerateBounded(dCounter.GetValue()) + 1;
179173
resultTotal += resultIndividual;
180174
lv_label_ins_text(resultIndividualLabel, LV_LABEL_POS_LAST, std::to_string(resultIndividual).c_str());
181175
if (i < (nCounter.GetValue() - 1)) {

‎src/displayapp/screens/Dice.h‎

Lines changed: 9 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -4,10 +4,11 @@
44
#include "displayapp/screens/Screen.h"
55
#include "displayapp/widgets/Counter.h"
66
#include "displayapp/Controllers.h"
7+
#include "components/rng/PCG.h"
78
#include "Symbols.h"
89

910
#include <array>
10-
#include <random>
11+
#include <cstdint>
1112

1213
namespace Pinetime {
1314
namespace Applications {
@@ -16,7 +17,8 @@ namespace Pinetime {
1617
public:
1718
Dice(Controllers::MotionController& motionController,
1819
Controllers::MotorController& motorController,
19-
Controllers::Settings& settingsController);
20+
Controllers::Settings& settingsController,
21+
Controllers::RNG& prngController);
2022
~Dice() override;
2123
void Roll();
2224
void Refresh() override;
@@ -29,7 +31,7 @@ namespace Pinetime {
2931
lv_task_t* refreshTask;
3032
bool enableShakeForDice = false;
3133

32-
std::mt19937 gen;
34+
Controllers::RNG rng;
3335

3436
std::array<lv_color_t, 3> resultColors = {LV_COLOR_YELLOW, LV_COLOR_MAGENTA, LV_COLOR_AQUA};
3537
uint8_t currentColorIndex;
@@ -54,7 +56,10 @@ namespace Pinetime {
5456
static constexpr const char* icon = Screens::Symbols::dice;
5557

5658
static Screens::Screen* Create(AppControllers& controllers) {
57-
return new Screens::Dice(controllers.motionController, controllers.motorController, controllers.settingsController);
59+
return new Screens::Dice(controllers.motionController,
60+
controllers.motorController,
61+
controllers.settingsController,
62+
*controllers.prngController);
5863
};
5964

6065
static bool IsAvailable(Pinetime::Controllers::FS& /*filesystem*/) {

‎src/displayapp/screens/Twos.cpp‎

Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -5,7 +5,8 @@
55

66
using namespace Pinetime::Applications::Screens;
77

8-
Twos::Twos() {
8+
Twos::Twos(Pinetime::Controllers::RNG& prngController) {
9+
rng = prngController.Seed();
910

1011
struct colorPair {
1112
lv_color_t bg;
@@ -86,9 +87,9 @@ bool Twos::placeNewTile() {
8687
return false; // game lost
8788
}
8889

89-
int random = rand() % nEmpty;
90+
int random = rng.GenerateBounded(nEmpty);
9091

91-
if ((rand() % 100) < 90) {
92+
if (rng.GenerateBounded(100) < 90) {
9293
grid[emptyCells[random] / nCols][emptyCells[random] % nCols].value = 2;
9394
} else {
9495
grid[emptyCells[random] / nCols][emptyCells[random] % nCols].value = 4;

‎src/displayapp/screens/Twos.h‎

Lines changed: 6 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -4,6 +4,8 @@
44
#include "displayapp/screens/Screen.h"
55
#include "displayapp/Controllers.h"
66

7+
#include "displayapp/screens/Dice.h"
8+
79
namespace Pinetime {
810
namespace Applications {
911
struct TwosTile {
@@ -14,7 +16,7 @@ namespace Pinetime {
1416
namespace Screens {
1517
class Twos : public Screen {
1618
public:
17-
Twos();
19+
Twos(Controllers::RNG& prngController);
1820
~Twos() override;
1921

2022
bool OnTouchEvent(TouchEvents event) override;
@@ -29,6 +31,7 @@ namespace Pinetime {
2931
static constexpr int nRows = 4;
3032
static constexpr int nCells = nCols * nRows;
3133
TwosTile grid[nRows][nCols];
34+
Controllers::RNG rng;
3235
unsigned int score = 0;
3336
void updateGridDisplay();
3437
bool tryMerge(int newRow, int newCol, int oldRow, int oldCol);
@@ -42,8 +45,8 @@ namespace Pinetime {
4245
static constexpr Apps app = Apps::Twos;
4346
static constexpr const char* icon = "2";
4447

45-
static Screens::Screen* Create(AppControllers& /*controllers*/) {
46-
return new Screens::Twos();
48+
static Screens::Screen* Create(AppControllers& controllers) {
49+
return new Screens::Twos(*controllers.prngController);
4750
};
4851

4952
static bool IsAvailable(Pinetime::Controllers::FS& /*filesystem*/) {

‎src/main.cpp‎

Lines changed: 6 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -37,6 +37,7 @@
3737
#include "components/heartrate/HeartRateController.h"
3838
#include "components/stopwatch/StopWatchController.h"
3939
#include "components/fs/FS.h"
40+
#include "components/rng/PCG.h"
4041
#include "drivers/Spi.h"
4142
#include "drivers/SpiMaster.h"
4243
#include "drivers/SpiNorFlash.h"
@@ -361,8 +362,12 @@ int main() {
361362
}
362363

363364
systemTask.Start();
364-
365365
nimble_port_init();
366+
// ble_ll functions should probably be called after ble_ll_init which is called from nimble_port_init
367+
Pinetime::Controllers::RNG::State prngBleInit;
368+
ble_ll_rand_data_get((uint8_t*) &prngBleInit, sizeof(prngBleInit));
369+
prngBleInit.state ^= (decltype(prngBleInit.state)) xTaskGetTickCount();
370+
systemTask.prngController.rng = prngBleInit;
366371

367372
vTaskStartScheduler();
368373

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