init

engines/cpp/main.cpp

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+/**
+ * engines/cpp/main.cpp
+ * --------------------
+ * C++ 动力学模拟引擎（模板/参考实现）。
+ *
+ * 接口与 C 引擎一致：
+ *   输入: param.json, <input_dir>/coord.txt, connection.txt, bond.txt
+ *   输出: <output_dir>/trajectory.txt (JSON)
+ *
+ * 编译:
+ *   g++ -O3 -march=native -o build/dynamics_cpp main.cpp
+ *
+ * 用法:
+ *   ./build/dynamics_cpp <input_dir> <output_dir> <param_json>
+ */
+
+#include <iostream>
+#include <fstream>
+#include <sstream>
+#include <string>
+#include <vector>
+#include <cmath>
+#include <chrono>
+#include <cstring>
+
+struct SimParams {
+    double box_a;
+    int NT;
+    double DT;
+    int NSTEP;
+    int warmup_steps;
+    double G[3];
+    double B[3];
+};
+
+struct Atom {
+    int id;
+    double mass, radius;
+    double x, y, z;
+    double vx, vy, vz;
+    bool fx, fy, fz;  // fixed constraints
+};
+
+struct Bond {
+    int i, j;
+    double stiffness, rest_length;
+};
+
+// ========================================================================
+// 请在下方实现 Leapfrog 算法
+// 参考 engines/c/main.c 中的物理核心实现
+// ========================================================================
+
+int main(int argc, char **argv) {
+    if (argc < 4) {
+        std::cerr << "用法: " << argv[0] << " <input_dir> <output_dir> <param_json>" << std::endl;
+        return 1;
+    }
+
+    std::string input_dir  = argv[1];
+    std::string output_dir = argv[2];
+    std::string param_path = argv[3];
+
+    auto t0 = std::chrono::high_resolution_clock::now();
+
+    // TODO: 读取 param.json、coord.txt、connection.txt、bond.txt
+    // TODO: 执行 Leapfrog 模拟
+    // TODO: 输出 trajectory.txt (JSON 格式)
+    //
+    // 提示：输出格式与 Python 版兼容，参考 engines/c/main.c 中的 write_trajectory_json
+
+    auto t1 = std::chrono::high_resolution_clock::now();
+    double elapsed = std::chrono::duration<double>(t1 - t0).count();
+
+    std::cout << "[C++-engine] 占位: NT=" << 0 << ", " << elapsed << " s (待实现)" << std::endl;
+    return 0;
+}