From e9cfa972d7ffd09584b678b42cb60bf50b8efa92 Mon Sep 17 00:00:00 2001
From: crupest <crupest@outlook.com>
Date: Fri, 11 Jun 2021 11:24:08 +0800
Subject: import(life): ...

---
 .../operating-system-experiment/CMakeLists.txt     |  2 +
 .../ParallelCalculationDemo.cpp                    | 73 ++++++++++++++++++++++
 2 files changed, 75 insertions(+)
 create mode 100644 works/life/operating-system-experiment/ParallelCalculationDemo.cpp

(limited to 'works/life')

diff --git a/works/life/operating-system-experiment/CMakeLists.txt b/works/life/operating-system-experiment/CMakeLists.txt
index c8afc24..5671b4a 100644
--- a/works/life/operating-system-experiment/CMakeLists.txt
+++ b/works/life/operating-system-experiment/CMakeLists.txt
@@ -31,3 +31,5 @@ target_link_libraries(interlocked_avoid_data_race_demo PRIVATE cru_system)
 add_executable(semaphore_avoid_data_race_demo SemaphoreAvoidDataRaceDemo.cpp)
 target_link_libraries(semaphore_avoid_data_race_demo PRIVATE cru_system)
 
+add_executable(parallel_calculation_demo ParallelCalculationDemo.cpp)
+target_link_libraries(parallel_calculation_demo PRIVATE cru_system)
diff --git a/works/life/operating-system-experiment/ParallelCalculationDemo.cpp b/works/life/operating-system-experiment/ParallelCalculationDemo.cpp
new file mode 100644
index 0000000..31ff2bf
--- /dev/null
+++ b/works/life/operating-system-experiment/ParallelCalculationDemo.cpp
@@ -0,0 +1,73 @@
+#include "Thread.h"
+
+#include <iostream>
+
+const long long N = 1e9;
+
+int main(int argc, char **argv) {
+  int thread_number;
+  if (argc == 1) {
+    thread_number = 1;
+  } else if (argc == 2) {
+    thread_number = std::atoi(argv[1]);
+    if (thread_number <= 0) {
+      std::cerr << "Argument must be a positive integer.\n";
+    }
+  } else {
+    std::cerr << "Too many arguments.\n";
+  }
+
+  std::cout << "Use " << thread_number << " threads to calculate sum of 1-" << N
+            << ".\n";
+
+  if (thread_number == 1) {
+    long long sum = 0;
+    for (long long i = 1; i <= 1e9; i++) {
+      sum += i;
+    }
+    std::cout << "Sum of 1-" << N << " is " << sum << '\n';
+  } else {
+    std::vector<cru::Thread> threads(thread_number);
+    std::vector<long long> partial_sum(thread_number);
+
+    long long step = N / thread_number;
+
+    for (int i = 0; i < thread_number; i++) {
+      long long start = step * i;
+      long long end = step * (i + 1);
+
+      long long &ps = partial_sum[i];
+
+      if (i == thread_number - 1) {
+        threads[i] = cru::Thread([&ps, start] {
+          long long sum = 0;
+          for (long long j = start; j <= 1e9; j++) {
+            sum += j;
+          }
+          ps = sum;
+        });
+      } else {
+        threads[i] = cru::Thread([&ps, start, end] {
+          long long sum = 0;
+          for (int j = start; j < end; j++) {
+            sum += j;
+          }
+          ps = sum;
+        });
+      }
+    }
+
+    for (auto &thread : threads) {
+      thread.Join();
+    }
+
+    long long sum = 0;
+    for (auto ps : partial_sum) {
+      sum += ps;
+    }
+
+    std::cout << "Sum of 1-" << N << " is " << sum << '\n';
+  }
+
+  return 0;
+}
-- 
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