golang: added Session.ListDevices method (#14385)

* golang: added Session.ListDevices method

tensorflow/go/session.go

@@ -65,6 +65,51 @@ func NewSession(graph *Graph, options *SessionOptions) (*Session, error) {
 	return s, nil
 }
 
+// Device structure contains information about a device associated with a session, as returned by ListDevices()
+type Device struct {
+	Name, Type       string
+	MemoryLimitBytes int64
+}
+
+// Return list of devices associated with a Session
+func (s *Session) ListDevices() ([]Device, error) {
+	var devices []Device
+
+	status := newStatus()
+	devices_list := C.TF_SessionListDevices(s.c, status.c)
+	if err := status.Err(); err != nil {
+		return nil, fmt.Errorf("SessionListDevices() failed: %v", err)
+	}
+	defer C.TF_DeleteDeviceList(devices_list)
+
+	for i := 0; i < int(C.TF_DeviceListCount(devices_list)); i++ {
+		device_name := C.TF_DeviceListName(devices_list, C.int(i), status.c)
+		if err := status.Err(); err != nil {
+			return nil, fmt.Errorf("DeviceListName(index=%d) failed: %v", i, err)
+		}
+
+		device_type := C.TF_DeviceListType(devices_list, C.int(i), status.c)
+		if err := status.Err(); err != nil {
+			return nil, fmt.Errorf("DeviceListType(index=%d) failed: %v", i, err)
+		}
+
+		memory_limit_bytes := C.TF_DeviceListMemoryBytes(devices_list, C.int(i), status.c)
+		if err := status.Err(); err != nil {
+			return nil, fmt.Errorf("DeviceListMemoryBytes(index=%d) failed: %v", i, err)
+		}
+
+		device := Device{
+			Name:             C.GoString(device_name),
+			Type:             C.GoString(device_type),
+			MemoryLimitBytes: int64(memory_limit_bytes),
+		}
+
+		devices = append(devices, device)
+	}
+
+	return devices, nil
+}
+
 // Run the graph with the associated session starting with the supplied feeds
 // to compute the value of the requested fetches. Runs, but does not return
 // Tensors for operations specified in targets.

tensorflow/go/session_test.go

@@ -283,3 +283,19 @@ func TestSessionConfig(t *testing.T) {
 		t.Fatalf("Got %v, want -1", output[0].Value())
 	}
 }
+
+func TestListDevices(t *testing.T) {
+	s, err := NewSession(NewGraph(), nil)
+	if err != nil {
+		t.Fatalf("NewSession(): %v", err)
+	}
+
+	devices, err := s.ListDevices()
+	if err != nil {
+		t.Fatalf("ListDevices(): %v", err)
+	}
+
+	if len(devices) == 0 {
+		t.Fatalf("no devices detected")
+	}
+}