[AutoParallel] fix reshard when train with eval (#46605)

* [AutoParallel] fix reshard when train with eval

* fix mppp

python/paddle/distributed/auto_parallel/reshard.py

@@ -1738,8 +1738,18 @@ class Resharder:
                 if len(set(process_mesh.processes)) == len(processes):
                     global_process_mesh_idx = idx
                     break
+
             if global_process_mesh_idx is not None:
-                self.dist_context.process_meshes.pop(idx)
+                is_removed = False
+                global_mesh = self.dist_context.process_meshes[idx]
+                for i, mesh in enumerate(self.dist_context.process_meshes):
+                    if i == idx:
+                        continue
+                    if set(mesh.processes) < set(global_mesh.processes):
+                        is_removed = True
+
+                if is_removed:
+                    self.dist_context.process_meshes.pop(idx)
 
     def _change_subblock_op_input_and_output(self, block_idx, block):
         if "var_reshard_mapping" in Resharder.while_block_info[block_idx]: