get gpu automatically rather than specify device_id (#3848)

* get gpu automatically rather than specify device_id

* fix param type

Author: fanlu

src/pybind/cudamatrix/cu_device_pybind.cc

@@ -36,6 +36,16 @@ void pybind_cu_device(py::module& m) {
         },
         py::arg("device_id"));
 
+  m.def("SelectGpuId",
+        [](const std::string& use_gpu) {
+#if HAVE_CUDA == 1
+          CuDevice::Instantiate().SelectGpuId(use_gpu);
+#else
+          KALDI_LOG << "Kaldi is NOT compiled with GPU! Ignore it.";
+#endif
+        },
+        py::arg("use_gpu"));
+  
   m.def("CuDeviceAllowMultithreading", []() {
 #if HAVE_CUDA == 1
     CuDevice::Instantiate().AllowMultithreading();