How do I know the GPU is working not CPU

[niceservo]

Hi, when I "import darknet" it shows "name 'DARKNET_FORCE_CPU' is not defined". When I "import darknet" a second time, it works lol. This command works fine with 30fps:
darknet.exe detector demo cfg/coco.data cfg/yolov4-tiny.cfg yolov4-tiny.weights -c 0
But, darknet.exe detector demo cfg/coco.data cfg/yolov4-tiny.cfg yolov4-tiny.weights -i 1 -c 0
shows CUDA status Error: file: C:\Users\wm\Desktop\darknet\darknet\src\dark_cuda.c : cuda_set_device()

With all these errors, how do I know that the GPU is actually working. If it works, wouldn't it be faster than 30fps in tiny? my makefile set to GPU 1