重做习题20-20，单独测量插入时间

README.md

@@ -544,7 +544,9 @@ $ ctest
 * [20-18~20-19](ch20/range_checked_iterator.h)
 * [20-20](ch20/exec20-20.cpp)
   * 编译命令：`g++ -std=c++14 -O2 -o exec20-20 exec20-20.cpp`
-  * [测试结果](ch20/exec20-20_result.csv)（看起来似乎不存在`list`比`vector`快的可能性）
+  * [测试结果](ch20/exec20-20_result.csv)
+  * [总时间](ch20/exec20-20_total_time.png)
+  * [插入时间](ch20/exec20-20_insert_time.png)
 
 ## 第21章 算法和映射
 ### 21.4 函数对象

ch20/exec20-20.cpp

@@ -10,19 +10,22 @@ using namespace std;
 using namespace std::chrono;
 
 template<class C>
-system_clock::duration time_ordered_insert(C& c, int N) {
+std::pair<system_clock::duration, system_clock::duration> time_ordered_insert(C& c, int N) {
     random_device rd;
     mt19937 generator(rd());
     uniform_int_distribution<int> distribution(0, N - 1);
 
     auto start = system_clock::now();
+    auto insert_time = system_clock::duration::zero();
     for (int i = 0; i < N; ++i) {
         int x = distribution(generator);
         auto it = find_if(c.begin(), c.end(), [x](int y) { return y > x; });
+        auto before_insert = system_clock::now();
         c.insert(it, x);
+        insert_time += system_clock::now() - before_insert;
     }
-    auto stop = system_clock::now();
-    return stop - start;
+    auto total_time = system_clock::now() - start;
+    return std::make_pair(total_time, insert_time);
 }
 
 // Generate N random int values in the range [0:N), insert into a vector and keep it sorted.
@@ -37,11 +40,13 @@ int main(int argc, char* argv[]) {
     using double_seconds = duration<double, seconds::period>;
 
     vector<int> v;
-    system_clock::duration vector_time = time_ordered_insert(v, N);
-    cout << "vector takes " << duration_cast<double_seconds>(vector_time).count() << " s" << endl;
+    auto vector_time = time_ordered_insert(v, N);
+    cout << "vector total time: " << duration_cast<double_seconds>(vector_time.first).count() << " s, "
+            << "insert time: " << duration_cast<double_seconds>(vector_time.second).count() << " s" << endl;
 
     list<int> l;
-    system_clock::duration list_time = time_ordered_insert(l, N);
-    cout << "list takes " << duration_cast<double_seconds>(list_time).count() << " s" << endl;
+    auto list_time = time_ordered_insert(l, N);
+    cout << "list total time: " << duration_cast<double_seconds>(list_time.first).count() << " s, "
+            << "insert time: " << duration_cast<double_seconds>(list_time.second).count() << " s" << endl;
     return 0;
 }

ch20/exec20-20_result.csv

@@ -1,14 +1,14 @@
-N,vector time (s),list time(s)
-10000,0.0120641,0.0912781
-20000,0.0481248,0.577694
-50000,0.295525,6.22311
-100000,1.213,30.2128
-200000,5.65612,133.626
-300000,13.096,319.202
-400000,24.0716,699.424
-500000,37.2407,1362.84
-600000,54.6855,2491.17
-700000,74.2577,4412.57
-800000,96.2638,6896.5
-900000,122.905,9786.17
-1000000,150.045,13834
+N,vector total time(s),list total time(s),vector insert time(s),list insert time(s)
+10000,0.0126521,0.0960283,0.0034532,0.00157586
+20000,0.0453952,0.590373,0.011398,0.00342591
+50000,0.265029,6.32425,0.0621942,0.00988026
+100000,1.08638,30.7264,0.274217,0.022183
+200000,5.0392,134.288,1.59602,0.0481346
+300000,11.6677,317.616,3.95115,0.0863665
+400000,21.0138,682.499,7.28008,0.149247
+500000,32.8607,1343.36,11.6863,0.222103
+600000,47.6211,2501.56,16.9675,0.302561
+700000,64.2485,4231.82,23.2764,0.481038
+800000,84.0283,6650.76,30.5704,0.651316
+900000,106.682,9842.69,39.2427,0.681576
+1000000,131.703,13541.2,48.4753,0.878751