* Initial Commit

CMakeLists.txt

+cmake_minimum_required(VERSION 3.10)
+
+project(
+    pi_monte_carlo 
+    VERSION 0.0.1
+    LANGUAGES CXX
+)
+
+# Find needed libraries #########################################
+
+find_package(MPI REQUIRED)
+
+
+# Setup the pi_monte_carlo library #####################################
+
+add_executable(
+    pi_monte_carlo
+
+    src/pi.cc
+)
+
+target_compile_features(pi_monte_carlo PUBLIC cxx_std_14)
+
+target_link_libraries(pi_monte_carlo PRIVATE ${MPI_CXX_LIBRARIES})
+
+target_include_directories(pi_monte_carlo PRIVATE ${MPI_CXX_INCLUDE_PATH})
+
+message(STATUS "MPI_CXX_LIBRARIES = ${MPI_CXX_LIBRARIES}")
+message(STATUS "MPI_CXX_INCLUDE_PATH = ${MPI_CXX_INCLUDE_PATH}")

README.md

+# Pi Monte Carlo
+
+## Build
+
+Execute `./build.sh`
+
+## Run
+
+Execute `mpirun ./build/pi_monte_carlo

build.sh

+#!/bin/bash
+
+script="${BASH_SOURCE[0]:-${(%):-%x}}"
+script_dir="$( cd "$( dirname "${script}" )" >/dev/null 2>&1 && pwd )"
+build_dir="${script_dir}/build"
+
+mkdir -p ${build_dir}
+pushd ${build_dir}
+
+cmake \
+    "${script_dir}"
+
+make -j 4 
+
+popd # build_dir

src/pi.cc

+#include <algorithm>
+#include <array>
+#include <chrono>
+#include <cmath>
+#include <iostream>
+#include <limits>
+#include <mpi.h>
+#include <random>
+#include <vector>
+
+const unsigned long long BATCH_SIZE  = 100000;
+const unsigned long long NUM_BATCHES = 10000000;
+
+std::vector<std::array<double, 2>> generate_random_pairs(
+    const unsigned long long& n, std::default_random_engine& rng)
+{
+    std::uniform_real_distribution<double> distribution(0, 1);
+    std::vector<std::array<double, 2>> batch(n);
+
+    std::for_each(batch.begin(), batch.end(), [&](std::array<double, 2>& pair) {
+        pair[0] = distribution(rng);
+        pair[1] = distribution(rng);
+    });
+
+    return batch;
+}
+
+bool is_hit(const std::array<double, 2>& pair)
+{
+    if (std::pow(pair[0], 2) + std::pow(pair[1], 2) <= 1) {
+        return true;
+    }
+    return false;
+}
+
+/* returns number of hits */
+unsigned long long run_batch(
+    const std::vector<std::array<double, 2>> coordinate_pairs)
+{
+    unsigned long long hits = 0;
+    std::for_each(
+        coordinate_pairs.begin(), coordinate_pairs.end(),
+        [&](std::array<double, 2> pair) {
+            if (is_hit(pair)) {
+                hits++;
+            }
+        });
+
+    return hits;
+}
+
+void print_pi(const double& hit_ratio)
+{
+    std::cout << "\r"
+              << "Pi = " << 4.0 * hit_ratio << std::flush;
+}
+
+int main(int argc, char* argv[])
+{
+    MPI_Init(&argc, &argv);
+    int rank, size;
+    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+    MPI_Comm_size(MPI_COMM_WORLD, &size);
+
+    std::default_random_engine rng(
+        std::chrono::system_clock::now().time_since_epoch().count());
+    std::cout.precision(std::numeric_limits<double>::max_digits10);
+
+    unsigned long long hits = 0;
+    for (unsigned long long i = 0; i < NUM_BATCHES; i++) {
+        std::vector<std::array<double, 2>> coordinate_pairs =
+            generate_random_pairs(BATCH_SIZE, rng);
+        hits += run_batch(coordinate_pairs);
+
+        unsigned long long global_hits = 0;
+        MPI_Reduce(
+            &hits, &global_hits, 1, MPI_UNSIGNED_LONG_LONG, MPI_SUM, 0,
+            MPI_COMM_WORLD);
+
+        if (rank == 0) {
+            unsigned long long attempts = (1 + i) * BATCH_SIZE * size;
+            print_pi(
+                static_cast<double>(global_hits)
+                / static_cast<double>(attempts));
+        }
+    }
+
+    MPI_Finalize();
+
+    return 0;
+}