Add Pack operator to TFLite (apache#3521)

python/tvm/relay/frontend/tflite.py

@@ -79,6 +79,7 @@ def __init__(self, model, subgraph, exp_tab):
             'REDUCE_PROD': self._convert_reduce_prod,
             'FULLY_CONNECTED': self.convert_fully_connected,
             'PAD': self.convert_pad,
+            'PACK': self.convert_pack,
             'LOGISTIC': self.convert_logistic,
         }
 
@@ -789,6 +790,33 @@ def convert_pad(self, op):
         out = _op.nn.pad(in_expr, paddings)
         return out
 
+    def convert_pack(self, op):
+        """Convert TFLite pack"""
+        try:
+            from tflite.BuiltinOptions import BuiltinOptions
+            from tflite.Operator import Operator
+            from tflite.PackOptions import PackOptions
+        except ImportError:
+            raise ImportError("The tflite package must be installed")
+
+        assert isinstance(op, Operator)
+        input_tensors = self.get_input_tensors(op)
+        assert len(input_tensors) >= 1, "input tensors should greater than 1"
+        in_exprs = [self.get_expr(input_tensor.tensor_idx) for input_tensor in input_tensors]
+
+        output_tensors = self.get_output_tensors(op)
+        assert len(output_tensors) == 1, "output tensors should be 1"
+
+        assert op.BuiltinOptionsType() == BuiltinOptions.PackOptions
+        op_options = op.BuiltinOptions()
+        pack_options = PackOptions()
+        pack_options.Init(op_options.Bytes, op_options.Pos)
+        pack_axis = pack_options.Axis()
+
+        in_exprs_reshaped = [_op.expand_dims(i, axis=pack_axis, num_newaxis=1) for i in in_exprs]
+        out = _op.concatenate(in_exprs_reshaped, pack_axis)
+        return out
+
     def get_expr(self, input_tensor_idx):
         return self.exp_tab.get_expr(get_tensor_name(self.subgraph, input_tensor_idx))
 

tests/python/frontend/tflite/test_forward.py

@@ -581,6 +581,41 @@ def test_forward_pad():
                np.array([[1, 1], [2, 2]], dtype=np.int32)])
 
 
+#######################################################################
+# Pack
+# -------------
+
+def _test_pack(data, axis):
+    """ One iteration of pack """
+
+    assert len(data) >= 1
+
+    with tf.Graph().as_default():
+        in_data = [
+            array_ops.placeholder(shape=tensor.shape, dtype=tensor.dtype, name="in_{}".format(idx))
+            for idx, tensor in enumerate(data)]
+        out = array_ops.pack(in_data, axis=axis)
+        name = ["in_{}:0".format(idx) for idx in range(len(data))]
+
+        compare_tflite_with_tvm(data, name, in_data, [out])
+
+
+def test_forward_pack():
+    """ Pack """
+    _test_pack(
+        [np.arange(6).reshape((1, 2, 1, 3)),
+        np.arange(6).reshape((1, 2, 1, 3))], 1)
+
+    _test_pack(
+        [np.arange(6).reshape((3, 2)),
+         np.arange(6).reshape((3, 2))], 1)
+
+    _test_pack(
+        [np.arange(6).reshape((2, 1, 1, 3)),
+         np.arange(6).reshape((2, 1, 1, 3)),
+         np.arange(6).reshape((2, 1, 1, 3))], 1)
+
+
 #######################################################################
 # Logistic
 # --------
@@ -750,6 +785,7 @@ def test_forward_ssd_mobilenet_v1():
     # Transforms
     test_forward_concatenation()
     test_forward_pad()
+    test_forward_pack()
     test_forward_reshape()
     test_all_resize()
     test_forward_squeeze()