def _init_runtime(self):
        """ Call _init_runtime under different CUDA_VISIBLE_DEVICES, you'll
            have workers that run on multiGPUs
        """
        if self.idx != 0:
            from tensorpack.models.registry import disable_layer_logging
            disable_layer_logging()
        self.predictor = OfflinePredictor(self.config)
        if self.idx == 0:
            with self.predictor.graph.as_default():
                describe_trainable_vars()
 Call _init_runtime under different CUDA_VISIBLE_DEVICES, you'll
            have workers that run on multiGPUs
        
tensorpack/predict/concurrency.py