add 添加加法的并行计算示例

include/math/util.h

@@ -22,6 +22,9 @@ namespace xlib {
     //最小公倍数
     int lcm(int a,int b);
     int lcm(const std::vector<int>&);
+
+    //多线程并行计算和
+    int parallelSum(const std::vector<int>& nums);
 }
 
 #endif /* util_h */

main.cpp

@@ -22,6 +22,10 @@ void setLog()
     LOG_SET(LOG_LEVEL::L_ALL);
     LOG_I("log dir:%s", xlib_log_dir.c_str());
     XLog::setWrite(true, xlib_log_dir.append("xlib.log"));
+
+    int numThreads = std::thread::hardware_concurrency();
+
+    LOG_I("numThreads = %d",numThreads);
 }
 
 void testHttp()
@@ -498,6 +502,26 @@ void testMath()
     auto com = combination(arr, 2);
 
     LOG_I("combination:\n%s", XString::toString(com).c_str());
+
+     std::vector<int> nums = {};
+     for(int i = 0 ; i< 1000000; i++){
+        nums.push_back(i);
+     }
+    auto start_time = std::chrono::high_resolution_clock::now();
+    int t = 0;
+    for(auto e: nums){
+        t+=e;
+    }
+    auto end_time = std::chrono::high_resolution_clock::now();
+    std::chrono::duration<double, std::milli> elapsed_time = end_time - start_time;
+
+    LOG_I("Single compute:time:%f 毫秒,result:%d",elapsed_time.count(),t);
+
+    auto parallel_start_time = std::chrono::high_resolution_clock::now();
+    int parallel_total = parallelSum(nums);
+    auto parallel_end_time = std::chrono::high_resolution_clock::now();
+    std::chrono::duration<double, std::milli> parallel_elapsed_time = parallel_end_time - parallel_start_time;
+    LOG_I("Parallel compute sum :time:%f 毫秒,result:%d",parallel_elapsed_time.count(),parallel_total);
 }
 
 void testGaussianElimination()
@@ -676,6 +700,6 @@ int main(int argc, char *argv[])
     testUrl();
     testSort();
     testSolveStandardSudoku();
-     testDecodeAndEncode();
+    testDecodeAndEncode();
     return 0;
 }

src/math/util.cpp

@@ -6,6 +6,8 @@
 //
 
 #include "math/math.h"
+#include <thread>
+#include <future>
 
 namespace xlib {
 
@@ -114,7 +116,7 @@ namespace xlib {
         if(0==a || b==0) return 0;
         a = a<0? -a:a;
         b = b<0? -b:b;
-        return a*b / gcd(a, b);
+        return a / gcd(a, b)*b;
     }
 
     int lcm(const std::vector<int>& nums){
@@ -128,4 +130,38 @@ namespace xlib {
         }
         return result;
     }
+
+    int parallelSum(const std::vector<int>& nums) {
+        int sum = 0;
+
+        std::vector<std::future<int>> futures;
+
+        int numThreads = std::thread::hardware_concurrency();
+        if(numThreads<2){
+            for(int n:nums){
+                sum+=n;
+            }
+            return sum;
+        }
+        int chunkSize = nums.size() / numThreads;
+
+        for (int i = 0; i < numThreads; i++) {
+            int start = i * chunkSize;
+            int end = (i == numThreads - 1) ? nums.size() : (i + 1) * chunkSize;
+
+            futures.push_back(std::async(std::launch::async, [start, end, &nums]() {
+                int localSum = 0;
+                for (int j = start; j < end; j++) {
+                    localSum += nums[j];
+                }
+                return localSum;
+            }));
+        }
+
+        for (auto& future : futures) {
+            sum += future.get();
+        }
+
+        return sum;
+    }
 }