c++ parallel sort algorithm example

userland/cpp/parallel_sort.cpp

@@ -0,0 +1,51 @@
+// https://cirosantilli.com/linux-kernel-module-cheat#cpp-parallel-algorithms
+
+#include <algorithm>
+#include <cassert>
+#include <chrono>
+#include <execution>
+#include <random>
+#include <iostream>
+#include <vector>
+
+int main(int argc, char **argv) {
+    using clk = std::chrono::high_resolution_clock;
+    decltype(clk::now()) start, end;
+    std::vector<unsigned long long> input_parallel, input_serial;
+    unsigned int seed;
+    unsigned long long n;
+
+    // CLI arguments;
+    std::uniform_int_distribution<uint64_t> zero_ull_max(0);
+    if (argc > 1) {
+        n = std::strtoll(argv[1], NULL, 0);
+    } else {
+        n = 10;
+    }
+    if (argc > 2) {
+        seed = std::stoi(argv[2]);
+    } else {
+        seed = std::random_device()();
+    }
+
+    // Calculate random inpu.
+    std::mt19937 prng(seed);
+    for (unsigned long long i = 0; i < n; ++i) {
+        input_parallel.push_back(zero_ull_max(prng));
+    }
+    input_serial = input_parallel;
+
+    // Sort and time parallel.
+    start = clk::now();
+    std::sort(std::execution::par_unseq, input_parallel.begin(), input_parallel.end());
+    end = clk::now();
+    std::cout << "parallel " << std::chrono::duration<float>(end - start).count() << " s" << std::endl;
+
+    // Sort and time serial.
+    start = clk::now();
+    std::sort(std::execution::seq, input_serial.begin(), input_serial.end());
+    end = clk::now();
+    std::cout << "serial   " << std::chrono::duration<float>(end - start).count() << " s" << std::endl;
+
+    assert(input_parallel == input_serial);
+}

userland/cpp/random.cpp

@@ -6,7 +6,8 @@
 int main(int argc, char **argv) {
     // Potentially expensive /dev/urandom read that waits for entropy.
     std::random_device dev;
-    std::mt19937 prng(dev());
+    auto seed = dev();
+    std::mt19937 prng(seed);
     std::uniform_int_distribution<uint64_t> zero_ull_max(0);
     std::uniform_int_distribution<uint8_t> one_to_six(1, 6);