Rack/src/engine.cpp

#include <vector>
#include <algorithm>
#include <chrono>
#include <thread>
#include <condition_variable>
#include <mutex>

#include <xmmintrin.h>
#include <pmmintrin.h>

#include "rack.hpp"
#include "engine.hpp"


namespace rack {

bool gPaused = false;
std::vector<Module*> gModules;
std::vector<Wire*> gWires;
bool gPowerMeter = false;

static bool running = false;
static float sampleRate = 44100.f;
static float sampleTime = 1.f / sampleRate;
static float sampleRateRequested = sampleRate;

static Module *resetModule = NULL;
static Module *randomizeModule = NULL;


/** Threads which obtain a VIPLock will cause wait() to block for other less important threads.
This does not provide the VIPs with an exclusive lock. That should be left up to another mutex shared between the less important thread.
*/
struct VIPMutex {
	int count = 0;
	std::condition_variable cv;
	std::mutex countMutex;

	/** Blocks until there are no remaining VIPLocks */
	void wait() {
		std::unique_lock<std::mutex> lock(countMutex);
		while (count > 0)
			cv.wait(lock);
	}
};

struct VIPLock {
	VIPMutex &m;
	VIPLock(VIPMutex &m) : m(m) {
		std::unique_lock<std::mutex> lock(m.countMutex);
		m.count++;
	}
	~VIPLock() {
		std::unique_lock<std::mutex> lock(m.countMutex);
		m.count--;
		lock.unlock();
		m.cv.notify_all();
	}
};


static std::mutex mutex;
static std::thread thread;
static VIPMutex vipMutex;

// Parameter interpolation
static Module *smoothModule = NULL;
static int smoothParamId;
static float smoothValue;


json_t *Param::toJson() {
	json_t *rootJ = json_object();

	// Infinite params should serialize to 0
	float v = (std::isfinite(minValue) && std::isfinite(maxValue)) ? value : 0.f;
	json_object_set_new(rootJ, "value", json_real(v));

	return rootJ;
}

void Param::fromJson(json_t *rootJ) {
	json_t *valueJ = json_object_get(rootJ, "value");
	if (valueJ)
		value = json_number_value(valueJ);
}


float Light::getBrightness() {
	// LEDs are diodes, so don't allow reverse current.
	// For some reason, instead of the RMS, the sqrt of RMS looks better
	return std::pow(std::fmaxf(0.f, value), 0.25f);
}

void Light::setBrightnessSmooth(float brightness, float frames) {
	float v = (brightness > 0.f) ? brightness * brightness : 0.f;
	if (v < value) {
		// Fade out light with lambda = framerate
		value += (v - value) * sampleTime * frames * 60.f;
	}
	else {
		// Immediately illuminate light
		value = v;
	}
}


void Wire::step() {
	float value = outputModule->outputs[outputId].value;
	inputModule->inputs[inputId].value = value;
}


void engineInit() {
}

void engineDestroy() {
	// Make sure there are no wires or modules in the rack on destruction. This suggests that a module failed to remove itself before the RackWidget was destroyed.
	assert(gWires.empty());
	assert(gModules.empty());
}

static void engineStep() {
	// Sample rate
	if (sampleRateRequested != sampleRate) {
		sampleRate = sampleRateRequested;
		sampleTime = 1.f / sampleRate;
		for (Module *module : gModules) {
			module->onSampleRateChange();
		}
	}

	// Events
	if (resetModule) {
		resetModule->onReset();
		resetModule = NULL;
	}
	if (randomizeModule) {
		randomizeModule->onRandomize();
		randomizeModule = NULL;
	}

	// Param smoothing
	{
		Module *localSmoothModule = smoothModule;
		int localSmoothParamId = smoothParamId;
		float localSmoothValue = smoothValue;
		if (localSmoothModule) {
			float value = localSmoothModule->params[localSmoothParamId].value;
			const float lambda = 60.0; // decay rate is 1 graphics frame
			float delta = localSmoothValue - value;
			float newValue = value + delta * lambda * sampleTime;
			if (value == newValue) {
				// Snap to actual smooth value if the value doesn't change enough (due to the granularity of floats)
				localSmoothModule->params[localSmoothParamId].value = localSmoothValue;
				smoothModule = NULL;
			}
			else {
				localSmoothModule->params[localSmoothParamId].value = newValue;
			}
		}
	}

	// Step modules
	for (Module *module : gModules) {
		std::chrono::high_resolution_clock::time_point startTime;
		if (gPowerMeter) {
			startTime = std::chrono::high_resolution_clock::now();

			module->step();

			auto stopTime = std::chrono::high_resolution_clock::now();
			float cpuTime = std::chrono::duration<float>(stopTime - startTime).count() * sampleRate;
			module->cpuTime += (cpuTime - module->cpuTime) * sampleTime / 0.5f;
		}
		else {
			module->step();
		}

		// Step ports
		for (Input &input : module->inputs) {
			if (input.active) {
				float value = input.value / 5.f;
				input.plugLights[0].setBrightnessSmooth(value);
				input.plugLights[1].setBrightnessSmooth(-value);
			}
		}
		for (Output &output : module->outputs) {
			if (output.active) {
				float value = output.value / 5.f;
				output.plugLights[0].setBrightnessSmooth(value);
				output.plugLights[1].setBrightnessSmooth(-value);
			}
		}
	}

	// Step cables by moving their output values to inputs
	for (Wire *wire : gWires) {
		wire->step();
	}
}

static void engineRun() {
	// Set CPU to flush-to-zero (FTZ) and denormals-are-zero (DAZ) mode
	// https://software.intel.com/en-us/node/682949
	_MM_SET_FLUSH_ZERO_MODE(_MM_FLUSH_ZERO_ON);
	_MM_SET_DENORMALS_ZERO_MODE(_MM_DENORMALS_ZERO_ON);

	// Every time the engine waits and locks a mutex, it steps this many frames
	const int mutexSteps = 64;
	// Time in seconds that the engine is rushing ahead of the estimated clock time
	double ahead = 0.0;
	auto lastTime = std::chrono::high_resolution_clock::now();

	while (running) {
		vipMutex.wait();

		if (!gPaused) {
			std::lock_guard<std::mutex> lock(mutex);
			for (int i = 0; i < mutexSteps; i++) {
				engineStep();
			}
		}

		double stepTime = mutexSteps * sampleTime;
		ahead += stepTime;
		auto currTime = std::chrono::high_resolution_clock::now();
		const double aheadFactor = 2.0;
		ahead -= aheadFactor * std::chrono::duration<double>(currTime - lastTime).count();
		lastTime = currTime;
		ahead = fmaxf(ahead, 0.0);

		// Avoid pegging the CPU at 100% when there are no "blocking" modules like AudioInterface, but still step audio at a reasonable rate
		// The number of steps to wait before possibly sleeping
		const double aheadMax = 1.0; // seconds
		if (ahead > aheadMax) {
			std::this_thread::sleep_for(std::chrono::duration<double>(stepTime));
		}
	}
}

void engineStart() {
	running = true;
	thread = std::thread(engineRun);
}

void engineStop() {
	running = false;
	thread.join();
}

void engineAddModule(Module *module) {
	assert(module);
	VIPLock vipLock(vipMutex);
	std::lock_guard<std::mutex> lock(mutex);
	// Check that the module is not already added
	auto it = std::find(gModules.begin(), gModules.end(), module);
	assert(it == gModules.end());
	gModules.push_back(module);
}

void engineRemoveModule(Module *module) {
	assert(module);
	VIPLock vipLock(vipMutex);
	std::lock_guard<std::mutex> lock(mutex);
	// If a param is being smoothed on this module, stop smoothing it immediately
	if (module == smoothModule) {
		smoothModule = NULL;
	}
	// Check that all wires are disconnected
	for (Wire *wire : gWires) {
		assert(wire->outputModule != module);
		assert(wire->inputModule != module);
	}
	// Check that the module actually exists
	auto it = std::find(gModules.begin(), gModules.end(), module);
	assert(it != gModules.end());
	// Remove it
	gModules.erase(it);
}

void engineResetModule(Module *module) {
	resetModule = module;
}

void engineRandomizeModule(Module *module) {
	randomizeModule = module;
}

static void updateActive() {
	// Set everything to inactive
	for (Module *module : gModules) {
		for (Input &input : module->inputs) {
			input.active = false;
		}
		for (Output &output : module->outputs) {
			output.active = false;
		}
	}
	// Set inputs/outputs to active
	for (Wire *wire : gWires) {
		wire->outputModule->outputs[wire->outputId].active = true;
		wire->inputModule->inputs[wire->inputId].active = true;
	}
}

void engineAddWire(Wire *wire) {
	assert(wire);
	VIPLock vipLock(vipMutex);
	std::lock_guard<std::mutex> lock(mutex);
	// Check wire properties
	assert(wire->outputModule);
	assert(wire->inputModule);
	// Check that the wire is not already added, and that the input is not already used by another cable
	for (Wire *wire2 : gWires) {
		assert(wire2 != wire);
		assert(!(wire2->inputModule == wire->inputModule && wire2->inputId == wire->inputId));
	}
	// Add the wire
	gWires.push_back(wire);
	updateActive();
}

void engineRemoveWire(Wire *wire) {
	assert(wire);
	VIPLock vipLock(vipMutex);
	std::lock_guard<std::mutex> lock(mutex);
	// Check that the wire is already added
	auto it = std::find(gWires.begin(), gWires.end(), wire);
	assert(it != gWires.end());
	// Set input to 0V
	wire->inputModule->inputs[wire->inputId].value = 0.0;
	// Remove the wire
	gWires.erase(it);
	updateActive();
}

void engineSetParam(Module *module, int paramId, float value) {
	module->params[paramId].value = value;
}

void engineSetParamSmooth(Module *module, int paramId, float value) {
	// If another param is being smoothed, jump value
	if (smoothModule && !(smoothModule == module && smoothParamId == paramId)) {
		smoothModule->params[smoothParamId].value = smoothValue;
	}
	smoothParamId = paramId;
	smoothValue = value;
	smoothModule = module;
}

void engineSetSampleRate(float newSampleRate) {
	sampleRateRequested = newSampleRate;
}

float engineGetSampleRate() {
	return sampleRate;
}

float engineGetSampleTime() {
	return sampleTime;
}

} // namespace rack