fix(jax): handle DPA-2 pbc/nopbc without mapping (#4363)

In the C++ API, generate the mapping for the no PBC and throw the error
for PBC. Considering I forgot setting `atom_modify map yes` when testing
it, others may also forget.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **New Features**
- Introduced a function to determine if the model supports message
passing, enhancing the model's interface.
- Added a private member variable to facilitate message passing
functionality.
- Implemented unit tests for the `DeepPot` class, validating its
functionality under various conditions.

- **Bug Fixes**
- Improved error handling for TensorFlow function retrieval, ensuring
more specific exceptions are thrown.
- Enhanced compatibility with earlier model versions by managing
exceptions related to the new message passing variable.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Signed-off-by: Jinzhe Zeng <jinzhe.zeng@rutgers.edu>

Author: njzjz

deepmd/jax/jax2tf/serialization.py

@@ -294,6 +294,12 @@ def get_model_def_script():
             )
 
         tf_model.get_model_def_script = get_model_def_script
+
+        @tf.function
+        def has_message_passing() -> tf.Tensor:
+            return tf.constant(model.has_message_passing(), dtype=tf.bool)
+
+        tf_model.has_message_passing = has_message_passing
         tf.saved_model.save(
             tf_model,
             model_file,

source/api_cc/include/DeepPotJAX.h

@@ -189,6 +189,8 @@ class DeepPotJAX : public DeepPotBackend {
   std::vector<int64_t> sel;
   // number of neighbors
   int nnei;
+  // do message passing
+  bool do_message_passing;
   // padding to nall
   int padding_to_nall = 0;
   // padding for nloc

source/api_cc/src/DeepPotJAX.cc

@@ -64,6 +64,12 @@ inline TF_DataType get_data_tensor_type(const std::vector<int64_t>& data) {
   return TF_INT64;
 }
 
+struct tf_function_not_found : public deepmd::deepmd_exception {
+ public:
+  tf_function_not_found() : deepmd_exception() {};
+  tf_function_not_found(const std::string& msg) : deepmd_exception(msg) {};
+};
+
 inline TFE_Op* get_func_op(TFE_Context* ctx,
                            const std::string func_name,
                            const std::vector<TF_Function*>& funcs,
@@ -72,7 +78,7 @@ inline TFE_Op* get_func_op(TFE_Context* ctx,
   TF_Function* func = NULL;
   find_function(func, funcs, func_name);
   if (func == NULL) {
-    throw std::runtime_error("Function " + func_name + " not found");
+    throw tf_function_not_found("Function " + func_name + " not found");
   }
   const char* real_func_name = TF_FunctionName(func);
   // execute the function
@@ -314,6 +320,13 @@ void deepmd::DeepPotJAX::init(const std::string& model,
   ntypes = type_map_.size();
   sel = get_vector<int64_t>(ctx, "get_sel", func_vector, device, status);
   nnei = std::accumulate(sel.begin(), sel.end(), decltype(sel)::value_type(0));
+  try {
+    do_message_passing = get_scalar<bool>(ctx, "do_message_passing",
+                                          func_vector, device, status);
+  } catch (tf_function_not_found& e) {
+    // compatibile with models generated by v3.0.0rc0
+    do_message_passing = false;
+  }
   inited = true;
 }
 
@@ -584,6 +597,15 @@ void deepmd::DeepPotJAX::compute(std::vector<ENERGYTYPE>& ener,
     for (size_t ii = 0; ii < nall_real; ii++) {
       mapping[ii] = lmp_list.mapping[fwd_map[ii]];
     }
+  } else if (nloc_real == nall_real) {
+    // no ghost atoms
+    for (size_t ii = 0; ii < nall_real; ii++) {
+      mapping[ii] = ii;
+    }
+  } else if (do_message_passing) {
+    throw deepmd::deepmd_exception(
+        "Mapping is required for a message passing model. If you are using "
+        "LAMMPS, set `atom_modify map yes`");
   }
   input_list[3] = add_input(op, mapping, mapping_shape, data_tensor[3], status);
   // fparam