fix serial number

paddle/fluid/operators/checkpoint_load_op.cc

@@ -176,7 +176,7 @@ to a file on disk.
     AddAttr<std::string>(
         "dir",
         "(string)"
-        "The \"file_path\" where the LoDTensor variables will be saved.")
+        "The \"dir\" where the checkpoint files will be loaded.")
         .AddCustomChecker(
             [](const std::string &path) { return !path.empty(); });
   }

paddle/fluid/operators/checkpoint_save_op.cc

@@ -94,10 +94,16 @@ class CheckpointSaveOp : public framework::OperatorBase {
     VLOG(1) << "CheckpointSaveOp get " << SERIAL_VAR
             << " value: " << serial_num;
 
-    if (serial_num->empty()) {
-      serial_num->append("0");
+    int serials = 0;
+    if (!serial_num->empty()) {
+      std::string::size_type sz;
+      serials = std::stoi(serial_num->data, &sz);
+      serials += 1;
     }
 
+    serial_num->clear();
+    serial_num->append(std::to_string(serials));
+
     std::string dir = GenePath(ck_dir, serial_num->c_str());
     VLOG(1) << "CheckpointSaveOp current dir: " << dir;
     bool is_present = FileExists(dir);