WIP: Parallelize Pso

libautoscoper/src/PSO.cpp

@@ -2,6 +2,11 @@
 #include <iostream>
 #include <string>
 #include <vector>
+#include <thread>
+#include <mutex>
+
+// Prevents multiple threads from writing to the same memory location
+std::mutex MTX;
 
 // New Particle Swarm Optimization
 float host_fitness_function(std::vector<float> x)
@@ -46,6 +51,27 @@ float getRandomClamped()
   return (float)rand() / (float)RAND_MAX;
 }
 
+void thread_handler(Particle* p, Particle* pBest, Particle* gBest, float OMEGA) {
+  // Update the velocities and positions
+  p->updateVelocityAndPosition(pBest, gBest, OMEGA);
+
+  // Get the NCC of the current particle
+  p->ncc_val = host_fitness_function(p->position);
+
+  // Update the pBest if the current particle is better
+  if (p->ncc_val < pBest->ncc_val) {
+    *pBest = *p;
+  }
+
+  // Critial Section
+  MTX.lock();
+  // Update the gBest if the current particle is better
+  if (p->ncc_val < gBest->ncc_val) {
+    *gBest = *p;
+  }
+  MTX.unlock();
+}
+
 void pso(std::vector<Particle*>* particles, Particle* gBest, unsigned int MAX_EPOCHS, unsigned int MAX_STALL)
 {
   int stall_iter = 0;
@@ -80,28 +106,20 @@ void pso(std::vector<Particle*>* particles, Particle* gBest, unsigned int MAX_EP
 
     *currentBest = *gBest; // We want this to be a copy not a pointer
 
+    // Create a thread for each particle
+    std::vector<std::thread> threads;
     for (int i = 0; i < NUM_OF_PARTICLES; i++)
     {
       p = particles->at(i); // We want these to be pointers not copies
       curPBest = pBest.at(i);
 
-      // Update the velocities and positions
-      p->updateVelocityAndPosition(curPBest, gBest, OMEGA);
-
-      // Get the NCC of the current particle
-      p->ncc_val = host_fitness_function(p->position);
-
-      // Update the pBest if the current particle is better
-      if (p->ncc_val < curPBest->ncc_val) {
-        *curPBest = *p;
-      }
-
-      // Update the gBest if the current particle is better
-      if (p->ncc_val < gBest->ncc_val) {
-        *gBest = *p;
-      }
+      threads.push_back(std::thread(thread_handler, p, curPBest, currentBest, OMEGA));
     }
 
+    // Wait for all threads to finish
+    for (auto& t : threads) t.join();
+
+    // Update the OMEGA
     OMEGA = OMEGA * 0.9f;
 
     std::cout << "Current Best NCC: " << gBest->ncc_val << std::endl;