CUDA_VISIBLE_DEVICES=1 python your_file.py

这样在跑你的网络之前，告诉程序只能看到1号GPU，其他的GPU它不可见

可用的形式如下：

CUDA_VISIBLE_DEVICES=1 Only device 1 will be seen
CUDA_VISIBLE_DEVICES=0,1 Devices 0 and 1 will be visible
CUDA_VISIBLE_DEVICES=”0,1” Same as above, quotation marks are optional
CUDA_VISIBLE_DEVICES=0,2,3 Devices 0, 2, 3 will be visible; device 1 is masked
CUDA_VISIBLE_DEVICES=”” No GPU will be visible

参考：
ubuntu 16.04上运行tensor flow 指定gpu