add onnx flatten

add description for clip to relu.

mace/python/tools/converter_tool/onnx_converter.py

@@ -89,7 +89,7 @@ OnnxSupportedOps = [
     # 'Expand',
     'ExtractPooling',
     # 'EyeLike',
-    # 'Flatten',
+    'Flatten',
     # 'Floor',
     # 'GRU',
     'Gather',
@@ -343,6 +343,7 @@ class OnnxConverter(base_converter.ConverterInterface):
             OnnxOpType.Div.name: self.convert_eltwise,
             OnnxOpType.Equal.name: self.convert_eltwise,
             OnnxOpType.ExtractPooling.name: self.convert_extract_pooling,
+            OnnxOpType.Flatten.name: self.convert_flatten,
             OnnxOpType.Gather.name: self.convert_gather,
             OnnxOpType.Gemm.name: self.convert_gemm,
             OnnxOpType.GlobalAveragePool.name: self.convert_reduce,
@@ -883,6 +884,9 @@ class OnnxConverter(base_converter.ConverterInterface):
             scale_arg.f = scale
 
     def convert_clip(self, node):
+        #  If clip's min value is zero,
+        #  convert clip to activation(ReLU or ReLUX)
+        #  so it can be fused into convolution.
         is_relux = False
         if 'min' in node.attrs:
             min_value = node.attrs['min']
@@ -1038,6 +1042,16 @@ class OnnxConverter(base_converter.ConverterInterface):
     def convert_flatten(self, node):
         op = self.convert_general_op(node)
         op.type = MaceOp.Reshape.name
+        axis_arg = op.arg.add()
+        axis_arg.name = MaceKeyword.mace_axis_str
+        axis_arg.i = 1
+        if 'axis' in node.attrs:
+            axis_arg.i = node.attrs['axis']
+        axis_arg.i = 4 + axis_arg.i if axis_arg.i < 0 else axis_arg.i
+
+        end_axis_arg = op.arg.add()
+        end_axis_arg.name = MaceKeyword.mace_end_axis_str
+        end_axis_arg.i = -1
 
     def convert_kaldi_batchnorm(self, node):
         op = self.convert_general_op(node)