add device info to tensor

test=develop

paddle/fluid/pybind/pybind.cc

@@ -295,6 +295,7 @@ PYBIND11_MODULE(core, m) {
       .def("_get_float_element", TensorGetElement<float>)
       .def("_set_double_element", TensorSetElement<double>)
       .def("_get_double_element", TensorGetElement<double>)
+      .def("_place", [](Tensor &self) { return self.place(); })
       .def("_dtype", [](Tensor &self) { return self.type(); });
 
   py::class_<LoDTensor, Tensor>(m, "LoDTensor", R"DOC(
@@ -673,6 +674,12 @@ All parameter, weight, gradient are variables in Paddle.
 
   py::class_<platform::Place>(m, "Place")
       .def(py::init<>())
+      .def("is_gpu_place",
+           [](platform::Place &self) { return platform::is_gpu_place(self); })
+      .def("gpu_device_id",
+           [](platform::Place &self) {
+             return boost::get<platform::CUDAPlace>(self).device;
+           })
       .def("set_place",
            [](platform::Place &self, const platform::CPUPlace &cpu_place) {
              self = cpu_place;