[MXNET-210]give warning for variables with same name in graph visualization

python/mxnet/visualization.py

@@ -26,7 +26,7 @@
 import re
 import copy
 import json
-
+import warnings
 from .symbol import Symbol
 
 def _str2tuple(string):
@@ -252,6 +252,15 @@ def plot_network(symbol, title="plot", save_format='pdf', shape=None, node_attrs
         shape_dict = dict(zip(interals.list_outputs(), out_shapes))
     conf = json.loads(symbol.tojson())
     nodes = conf["nodes"]
+    # check if multiple nodes have the same name
+    if len(nodes) != len(set([node["name"] for node in nodes])):
+        seen_nodes = set()
+        # find all repeated names
+        repeated = set(node['name'] for node in nodes if node['name'] in seen_nodes
+                       or seen_nodes.add(node['name']))
+        warning_message = "There are multiple variables with the same name in your graph, " \
+                          "this may result in cyclic graph. Repeated names: " + ','.join(repeated)
+        warnings.warn(warning_message, RuntimeWarning)
     # default attributes of node
     node_attr = {"shape": "box", "fixedsize": "true",
                  "width": "1.3", "height": "0.8034", "style": "filled"}

tests/python/unittest/test_viz.py

@@ -15,8 +15,12 @@
 # specific language governing permissions and limitations
 # under the License.
 
+import unittest
+import warnings
+
 import mxnet as mx
 
+
 def test_print_summary():
     data = mx.sym.Variable('data')
     bias = mx.sym.Variable('fc1_bias', lr_mult=1.0)
@@ -32,5 +36,29 @@ def test_print_summary():
     shape["data"]=(1,3,28,28)
     mx.viz.print_summary(sc1, shape)
 
+def graphviz_exists():
+    try:
+        import graphviz
+    except ImportError:
+        return False
+    else:
+        return True
+
+@unittest.skipIf(not graphviz_exists(), "Skip test_plot_network as Graphviz could not be imported")
+def test_plot_network():
+    # Test warnings for cyclic graph
+    net = mx.sym.Variable('data')
+    net = mx.sym.FullyConnected(data=net, name='fc', num_hidden=128)
+    net = mx.sym.Activation(data=net, name='relu1', act_type="relu")
+    net = mx.sym.FullyConnected(data=net, name='fc', num_hidden=10)
+    net = mx.sym.SoftmaxOutput(data=net, name='out')
+    with warnings.catch_warnings(record=True) as w:
+        digraph = mx.viz.plot_network(net, shape={'data': (100, 200)},
+                                      node_attrs={"fixedsize": "false"})
+    assert len(w) == 1
+    assert "There are multiple variables with the same name in your graph" in str(w[-1].message)
+    assert "fc" in str(w[-1].message)
+
 if __name__ == "__main__":
-    test_print_summary()
+    import nose
+    nose.runmodule()