Before revision:  This results in perfect performance for a large range of matrix sizes in the domain of interest , and at least 2/3 of maximum performance for the rest on an Nvidia Volta GPGPU.
After revision:  This results in perfect performance for a large range of matrix sizes in the domain of interest , and at least 2/3 of the roofline performance and often substantially outperform state-of-the art CUBLAS results on an NVIDIA Volta GPGPU.