improve conversion for gather op

x2paddle/op_mapper/onnx_op_mapper.py

@@ -567,9 +567,9 @@ class ONNXOpMapper(OpMapper):
         val_x = self.graph.get_input_node(node, idx=0, copy=True)
         indices = self.graph.get_input_node(node, idx=1, copy=True)
         indices_shape = indices.out_shapes[0]
-        axis = node.get_attr('axis')
+        axis = node.get_attr('axis', 0)
         assert len(
-            indices_shape) <= 1, "Gather op don't support dim of indice >1 "
+            indices_shape) <= 2, "Gather op don't support dim of indice >2 "
         if axis == 0 and len(indices_shape) <= 1:
             node.fluid_code.add_layer('gather',
                                       inputs={
@@ -598,6 +598,45 @@ class ONNXOpMapper(OpMapper):
                                       inputs=node,
                                       output=node,
                                       param_attr=attr_trans)
+        elif len(indices_shape) > 1:
+            from functools import reduce
+            reshape_shape = reduce(lambda x, y: x * y, indices_shape)
+            node.fluid_code.add_layer('reshape',
+                                      inputs=indices,
+                                      output=indices,
+                                      param_attr={'shape': [
+                                          reshape_shape,
+                                      ]})
+
+            perm = list(range(len(val_x.out_shapes[0])))
+            perm = [axis] + perm[:axis] + perm[axis + 1:]
+            attr_trans = {'perm': perm}
+            name_trans = val_x.layer_name + '_trans'
+            node.fluid_code.add_layer('transpose',
+                                      inputs=val_x,
+                                      output=name_trans,
+                                      param_attr=attr_trans)
+            node.fluid_code.add_layer('gather',
+                                      inputs={
+                                          'input': name_trans,
+                                          'index': indices
+                                      },
+                                      output=node,
+                                      param_attr=None)
+            node.fluid_code.add_layer('transpose',
+                                      inputs=node,
+                                      output=node,
+                                      param_attr=attr_trans)
+            val_x_shape = val_x.out_shapes[0]
+            reshaped_shape = []
+            for i in perm:
+                reshaped_shape.append(indices_shape[i])
+            for i in val_x_shape[:axis] + val_x_shape[axis + 1:]:
+                reshaped_shape.append(i)
+            node.fluid_code.add_layer('reshape',
+                                      inputs=node,
+                                      output=node,
+                                      param_attr={'shape': reshaped_shape})
 
     def Slice(self, node):
         val_x = self.graph.get_input_node(node, idx=0, copy=True)