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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 64 bits and has a equidistributed 2^32 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
1 parent 66b5977 commit 2c13cd8

12 files changed

Lines changed: 155 additions & 25 deletions

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‎src/CMakeLists.txt‎

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@@ -473,6 +473,8 @@ list(APPEND SOURCE_FILES
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components/stopwatch/StopWatchController.cpp
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components/alarm/AlarmController.cpp
475475
components/fs/FS.cpp
476+
components/rng/PCG.cpp
477+
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drivers/Cst816s.cpp
477479
FreeRTOS/port.c
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FreeRTOS/port_cmsis_systick.c
@@ -662,6 +664,7 @@ set(INCLUDE_FILES
662664
components/timer/Timer.h
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components/stopwatch/StopWatchController.h
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components/alarm/AlarmController.h
667+
components/rng/PCG.h
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drivers/Cst816s.h
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FreeRTOS/portmacro.h
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FreeRTOS/portmacro_cmsis.h

‎src/components/rng/PCG.cpp‎

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@@ -0,0 +1,66 @@
1+
#include "components/rng/PCG.h"
2+
3+
Pinetime::Controllers::RNG::State Pinetime::Controllers::RNG::Seed() {
4+
using namespace Pinetime::Controllers;
5+
Pinetime::Controllers::RNG::State new_rng;
6+
new_rng.state = (RNG::rng_uint) Generate() << (sizeof(new_rng.state) * 4) ^ (RNG::rng_uint) Generate();
7+
new_rng.inc = (RNG::rng_uint) Generate() << (sizeof(new_rng.inc) * 4) ^ (RNG::rng_uint) Generate();
8+
return new_rng;
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}
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// *Really* minimal PCG32 code / (c) 2014 M.E. O'Neill / pcg-random.org
12+
// Licensed under Apache License 2.0 (NO WARRANTY, etc. see website)
13+
// Website: https://www.pcg-random.org/download.html
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// See: https://www.apache.org/licenses/GPL-compatibility.html
15+
/*
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uint64_t oldstate = rng.state;
17+
// Advance internal state
18+
rng.state = oldstate * 6364136223846793005ULL + (rng.inc | 1);
19+
// Calculate output function (XSH RR), uses old state for max ILP
20+
uint32_t xorshifted = ((oldstate >> 18u) ^ oldstate) >> 27u;
21+
uint32_t rot = oldstate >> 59u;
22+
return (xorshifted >> rot) | (xorshifted << ((-rot) & 31));
23+
*/
24+
Pinetime::Controllers::RNG::rng_uint Pinetime::Controllers::RNG::Generate() {
25+
using namespace Pinetime::Controllers;
26+
// See magic numbers in https://github.com/imneme/pcg-cpp/blob/master/include/pcg_random.hpp
27+
constexpr uint32_t tbits = sizeof(rng.state) * 8;
28+
constexpr uint32_t sbits = sizeof(rng) * 8;
29+
30+
constexpr rng_uint multiplier = tbits >= 64 ? 1442695040888963407ULL : tbits >= 32 ? 747796405U : tbits >= 16 ? 12829U : 141u;
31+
32+
constexpr uint32_t opbits = sbits - 5 >= 64 ? 5u : // 128 bits -> 5
33+
sbits - 4 >= 32 ? 4u
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: // 64 bits -> 4
35+
sbits - 3 >= 16 ? 3u
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: // 32 bits -> 3
37+
sbits - 2 >= 8 ? 2u
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: // 16 bits -> 2
39+
sbits - 1 >= 1 ? 1u
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: // 8 bits -> 1
41+
0u;
42+
43+
auto oldstate = rng.state;
44+
rng.state = oldstate * multiplier + (rng.inc | 1);
45+
46+
constexpr rng_uint mask = (1u << opbits) - 1;
47+
constexpr rng_uint shift = opbits + (tbits + mask) / 2;
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49+
rng_uint xorshifted = ((oldstate >> shift) ^ oldstate) >> (tbits - opbits); // 16-4
50+
rng_uint rot = oldstate >> (sbits - opbits); // 32-4
51+
return (xorshifted >> rot) | (xorshifted << ((-rot) & mask));
52+
};
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54+
// Lemire's Method (slight rewrite) [0, range)
55+
Pinetime::Controllers::RNG::rng_uint Pinetime::Controllers::RNG::GenerateBounded(Pinetime::Controllers::RNG::rng_uint range) {
56+
using namespace Pinetime::Controllers;
57+
rng_uint2 m;
58+
rng_uint t = (-range) % range;
59+
rng_uint l;
60+
do {
61+
rng_uint x = Generate();
62+
m = rng_uint2(x) * rng_uint2(range);
63+
l = rng_uint(m);
64+
} while (l < t);
65+
return m >> 16;
66+
};

‎src/components/rng/PCG.h‎

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@@ -0,0 +1,41 @@
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#pragma once
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#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+
13+
struct pcg_random_t {
14+
rng_uint state = {};
15+
rng_uint inc = {};
16+
};
17+
18+
using State = pcg_random_t;
19+
State rng = {};
20+
21+
// Generate another RNG struct with data generated via this one
22+
State Seed();
23+
// Produces an unsigned result within the full range of the data type
24+
rng_uint Generate();
25+
// Produces an unsigned result within [0, range)
26+
rng_uint GenerateBounded(rng_uint range);
27+
28+
RNG() : rng() {};
29+
30+
RNG& operator=(const State& pcg_state) {
31+
rng = pcg_state;
32+
};
33+
34+
RNG(State pcg_state) {
35+
rng = pcg_state;
36+
};
37+
38+
~RNG() = default;
39+
};
40+
}
41+
}

‎src/displayapp/Controllers.h‎

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Original file line numberDiff line numberDiff line change
@@ -26,6 +26,7 @@ namespace Pinetime {
2626
class Timer;
2727
class MusicService;
2828
class NavigationService;
29+
class RNG;
2930
}
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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
}
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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 {
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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();
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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);
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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

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@@ -4,10 +4,13 @@
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>
12+
13+
1114

1215
namespace Pinetime {
1316
namespace Applications {
@@ -16,7 +19,8 @@ namespace Pinetime {
1619
public:
1720
Dice(Controllers::MotionController& motionController,
1821
Controllers::MotorController& motorController,
19-
Controllers::Settings& settingsController);
22+
Controllers::Settings& settingsController,
23+
Controllers::RNG& prngController);
2024
~Dice() override;
2125
void Roll();
2226
void Refresh() override;
@@ -29,7 +33,7 @@ namespace Pinetime {
2933
lv_task_t* refreshTask;
3034
bool enableShakeForDice = false;
3135

32-
std::mt19937 gen;
36+
Controllers::RNG rng;
3337

3438
std::array<lv_color_t, 3> resultColors = {LV_COLOR_YELLOW, LV_COLOR_MAGENTA, LV_COLOR_AQUA};
3539
uint8_t currentColorIndex;
@@ -54,7 +58,10 @@ namespace Pinetime {
5458
static constexpr const char* icon = Screens::Symbols::dice;
5559

5660
static Screens::Screen* Create(AppControllers& controllers) {
57-
return new Screens::Dice(controllers.motionController, controllers.motorController, controllers.settingsController);
61+
return new Screens::Dice(controllers.motionController,
62+
controllers.motorController,
63+
controllers.settingsController,
64+
*controllers.prngController);
5865
};
5966

6067
static bool IsAvailable(Pinetime::Controllers::FS& /*filesystem*/) {

‎src/displayapp/screens/Twos.cpp‎

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@@ -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

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@@ -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

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@@ -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"
@@ -359,10 +360,15 @@ int main() {
359360
memset(&__start_noinit_data, 0, (uintptr_t) &__stop_noinit_data - (uintptr_t) &__start_noinit_data);
360361
NoInit_MagicWord = NoInit_MagicValue;
361362
}
362-
363+
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;
371+
366372

367373
vTaskStartScheduler();
368374

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