✨ Finished assignment #2.

answers/02/pi_numerical_integration.cpp

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+#include <iomanip>
+#include <iostream>
+#include <omp.h>
+
+using namespace std;
+
+int main() {
+  int num_steps = 100000000; // number of rectangles
+  double width = 1.0 / double(num_steps); // width of a rectangle
+  double sum = 0.0; // for summing up all heights of rectangles
+
+  double start_time = omp_get_wtime(); // wall clock time in seconds
+  #pragma omp parallel for reduction(+:sum)
+  for (int i = 0; i < num_steps; i++) {
+    double x = (i + 0.5) * width; // midpoint
+    sum = sum + (1.0 / (1.0 + x * x)); // add new height of a rectangle
+  }
+  double pi = sum * 4 * width; // compute pi
+  double run_time = omp_get_wtime() - start_time;
+
+  cout << "pi with " << num_steps << " steps is " << setprecision(17)
+       << pi << " in " << setprecision(6) << run_time << " seconds\n";
+}