Perf: load data systems on rank 0

deepmd/pt/utils/dataloader.py

@@ -87,26 +87,23 @@
             with h5py.File(systems) as file:
                 systems = [os.path.join(systems, item) for item in file.keys()]
 
-        self.systems: list[DeepmdDataSetForLoader] = []
-        if len(systems) >= 100:
-            log.info(f"Constructing DataLoaders from {len(systems)} systems")
-
         def construct_dataset(system):
             return DeepmdDataSetForLoader(
                 system=system,
                 type_map=type_map,
             )
 
-        with Pool(
-            os.cpu_count()
-            // (
-                int(os.environ["LOCAL_WORLD_SIZE"])
-                if dist.is_available() and dist.is_initialized()
-                else 1
-            )
-        ) as pool:
-            self.systems = pool.map(construct_dataset, systems)
-
+        self.systems: list[DeepmdDataSetForLoader] = []
+        global_rank = dist.get_rank() if dist.is_initialized() else 0
+        if global_rank == 0:
+            log.info(f"Constructing DataLoaders from {len(systems)} systems")
+            with Pool(os.cpu_count()) as pool:
+                self.systems = pool.map(construct_dataset, systems)
+        else:
+            self.systems = [None] * len(systems)  # type: ignore
+        if dist.is_initialized():
+            dist.broadcast_object_list(self.systems)
+            assert self.systems[-1] is not None
         self.sampler_list: list[DistributedSampler] = []
         self.index = []
         self.total_batch = 0