add an error message for copress/freeze

deepmd/entrypoints/compress.py

@@ -137,7 +137,15 @@ def compress(
     # stage 2: freeze the model
     log.info("\n\n")
     log.info("stage 2: freeze the model")
-    freeze(checkpoint_folder=checkpoint_folder, output=output, node_names=None)
+    try:
+        freeze(checkpoint_folder=checkpoint_folder, output=output, node_names=None)
+    except GraphTooLargeError as e:
+        raise RuntimeError(
+            "The uniform step size of the tabulation's first table is %f, " 
+            "which is too small. This leads to a very large graph size, "
+            "exceeding protobuf's limitation (2 GB). You should try to "
+            "increase the step size." % step
+        ) from e
 
 def _check_compress_type(model_file):
     try:

deepmd/entrypoints/freeze.py

@@ -200,7 +200,14 @@ def freeze(
 
     # We retrieve the protobuf graph definition
     graph = tf.get_default_graph()
-    input_graph_def = graph.as_graph_def()
+    try:
+        input_graph_def = graph.as_graph_def()
+    except google.protobuf.message.DecodeError as e:
+        raise GraphTooLargeError(
+            "The graph size exceeds 2 GB, the hard limitation of protobuf."
+            " Then a DecodeError was raised by protobuf. You should "
+            "reduce the size of your model."
+        ) from e
     nodes = [n.name for n in input_graph_def.node]
 
     # We start a session and restore the graph weights

deepmd/utils/errors.py

@@ -1,5 +1,5 @@
 class GraphTooLargeError(Exception):
-    pass
+    """The graph is too large, exceeding protobuf's hard limit of 2GB."""
 
 class GraphWithoutTensorError(Exception):
     pass