SignOpt L2 norm runs so slow?

[machanic]

When I attack one image using a 1080Ti GPU, it consumes 30 minutes for attacking just 1 image! Too slow, how you suggest to accelerate the attack speed. I am checking the reason of running slow. Can you help me?

[cmhcbb]

I haven't met such a problem before. Please check whether you have correctly used the GPU.