add script to run optimizer on onnx files (#1538)

* add script to run optimizer on onnx files

Signed-off-by: Guenther Schmuelling <guschmue@microsoft.com>

* pylint

Signed-off-by: Guenther Schmuelling <guschmue@microsoft.com>

tools/onnx-optimize.py

@@ -0,0 +1,67 @@
+# SPDX-License-Identifier: Apache-2.0
+
+
+"""
+A simple tool to try optimizations on onnx graphs.
+This makes use of the fact that tensorflow-onnx internal graph representation is onnx
+so all graph, rewrite, matching and utility libaries do work which makes things easy.
+"""
+
+# pylint: disable=invalid-name,missing-docstring, unused-argument
+
+import argparse
+import logging
+
+import onnx
+from onnx import helper
+
+from tf2onnx.graph import GraphUtil
+from tf2onnx import logging, optimizer
+
+
+logging.basicConfig(level=logging.INFO)
+logger = logging.getLogger("onnx-optimize")
+
+
+def get_args():
+    """Parse commandline."""
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--input", required=True, help="onnx input model file")
+    parser.add_argument("--output", help="output model file")
+    args = parser.parse_args()
+    return args
+
+
+def load_graph(fname):
+    model_proto = onnx.ModelProto()
+    with open(fname, "rb") as f:
+        data = f.read()
+        model_proto.ParseFromString(data)
+    g = GraphUtil.create_graph_from_onnx_model(model_proto)
+    return g, model_proto
+
+
+def main():
+    args = get_args()
+
+    g, org_model_proto = load_graph(args.input)
+
+    g = optimizer.optimize_graph(g)
+
+    onnx_graph = g.make_graph(org_model_proto.graph.doc_string + " (+tf2onnx/onnx-optimize)")
+
+    kwargs = {"producer_name": org_model_proto.producer_name,
+              "producer_version": org_model_proto.producer_version,
+              "opset_imports": org_model_proto.opset_import,
+              "ir_version": org_model_proto.ir_version}
+
+    model_proto = helper.make_model(onnx_graph, **kwargs)
+
+    # write onnx graph
+    if args.output:
+        with open(args.output, "wb") as f:
+            f.write(model_proto.SerializeToString())
+
+
+if __name__ == "__main__":
+    main()