fix(pt): keep mapping not none during lmp steps when nghost == 0 (#4209)

enhancement on #4144 <!-- This is an auto-generated comment: release notes by coderabbit.ai --> ## Summary by CodeRabbit - **New Features** - Enhanced tensor mapping capabilities with the addition of a new `mapping_tensor` variable. - Updated `compute` method to handle ghost atoms and support improved tensor creation logic.	- Overloaded `computew` methods to support both double and float types. - **Bug Fixes** - Improved error handling in the `translate_error` method for better exception management. <!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: CaRoLZhangxy

source/api_cc/include/DeepPotPT.h

@@ -338,6 +338,7 @@ class DeepPotPT : public DeepPotBase {
  int do_message_passing; // 1:dpa2 model 0:others
  bool gpu_enabled;
  at::Tensor firstneigh_tensor;
+ c10::optional<torch::Tensor> mapping_tensor;
  torch::Dict<std::string, torch::Tensor> comm_dict;
  /**
  * @brief Translate PyTorch exceptions to the DeePMD-kit exception.

source/api_cc/src/DeepPotPT.cc

@@ -164,7 +164,6 @@ void DeepPotPT::compute(ENERGYVTYPE& ener,
  std::vector<std::int64_t> atype_64(datype.begin(), datype.end());
  at::Tensor atype_Tensor =
  torch::from_blob(atype_64.data(), {1, nall_real}, int_option).to(device);
- c10::optional<torch::Tensor> mapping_tensor;
  if (ago == 0) {
  nlist_data.copy_from_nlist(lmp_list);
  nlist_data.shuffle_exclude_empty(fwd_map);