Try to implement monte carlo simulation (#3)

Author: RaphaelRevivor

src/BUILD

@@ -8,6 +8,16 @@ cc_library(
   ],
 )
 
+cc_library(
+  name = "montecarloLib",
+  srcs = [
+    "montecarlo.cpp"
+  ],
+  hdrs = [
+    "montecarlo.h"
+  ],
+)
+
 cc_binary(
   name = "mainProg",
   srcs = [
@@ -16,5 +26,6 @@ cc_binary(
   ],
   deps = [
     ":factorLib",
+    ":montecarloLib",
   ], 
 )

src/main.cpp

@@ -25,4 +25,8 @@ int main(int argc, char** argv)
     cout << result << ",";
   }
   cout << endl;
+
+  auto monteCarloPi = MonteCarloPi();
+  double pi = monteCarloPi.estimatePi();
+  cout << "The estimated pi is: " << pi << endl;
 }

src/main.h

@@ -4,5 +4,6 @@
 #include <iostream>
 #include <stdexcept>
 #include "factor.h"
+#include "montecarlo.h"
 
 #endif

src/montecarlo.cpp

@@ -1,14 +1,35 @@
 #include "montecarlo.h"
 
 const int NUM = 4;
-const int NUM_EACH_THREAD = 10000;
+const int NUM_EACH_THREAD = 10000000;
 
-double MonteCarloPi::estimatePiSingleThread()
+void MonteCarloPi::estimatePiSingleThread()
 {
-
+  random_device rd;
+  // mersenne_twister_engine seeded with rd()
+  mt19937 gen(rd());
+  uniform_int_distribution<> distrib(0.0, 1.0);
+  for(int i = 0; i < NUM_EACH_THREAD; i++)
+  {
+    double x = distrib(gen);
+    double y = distrib(gen);
+    if (x*x + y*y <= 1.0)
+      insideCircle++;
+  }
 }
 
-void MonteCarloPi::estimatePi()
+double MonteCarloPi::estimatePi()
 {
-  // 4 threads, each threads do calculation 10000 times
+  for(int i = 0; i < NUM; i++)
+  {
+    threads.emplace_back(&MonteCarloPi::estimatePiSingleThread, this);
+  }
+
+  for(auto& t : threads)
+  {
+    t.join();
+  }
+
+  // return pi here
+  return (4.0 * insideCircle / (NUM * NUM_EACH_THREAD));
 }

src/montecarlo.h

@@ -10,13 +10,17 @@ using namespace std;
 class MonteCarloPi
 {
 public:
-  double estimatePiSingleThread();
-  void estimatePi();
+  MonteCarloPi& operator=(const MonteCarloPi&) = delete;
+
+  MonteCarloPi() = default;
+  ~MonteCarloPi() = default;
+
+  void estimatePiSingleThread();
+  double estimatePi();
 
 private:
   vector<thread> threads = {};
   atomic<int> insideCircle = 0;
-
 };
 
 #endif