[VTA] Running Tensorflow code in VTA simulation gives `c_runtime_api.cc` error

@tqchen @Ravenwater I just modified the TensorFlow graph to use uint8 as data type but still it doesn’t run. The same error messages appear. In short, the step that I import the graph and compile it with nnvm looks like this:

with tf.gfile.GFile('graph.pb', 'rb') as f:
    graph_def = tf.GraphDef()
    graph_def.ParseFromString(f.read())

with tf.Graph().as_default() as graph:
    tf.import_graph_def(graph_def, name='')
    sym, params = nnvm.frontend.from_tensorflow(graph_def)  # <----------

    shape_dict = {'input': (1, height, width, 3)}
    dtype_dict = {'input': 'uint8'}
    with vta.build_config():
        graph, lib, params = nnvm.compiler.build(graph=sym,  # <---------
                                                 shape=shape_dict,
                                                 dtype=dtype_dict,
                                                 target=target,
                                                 params=params,
                                                 target_host=target_host)
    ...
    m = graph_runtime.create(graph, lib, ctx)  # <------------------------

I believe the problem is either:

  1. I didn’t call the APIs properly.
  2. It might be because the graph fed to nnvm.frontend.from_tensorflow() is not compatible. But that is questionable to me because the graph is very simple. I attached the graph picture below.