In the model Tesla K20 the peak single-precision floating point performance is about 3.52 TFlops but the double-precision is 1.17 TFlops,so the ratio is 3. The Tesla K20X has 3.95 and 1.31, and Tesla K40 has 4.29 and 1.43 TFlops, the ratio seems to repeat. My question is if there is a reason to the ratio be 3 and not 2, that seems logical to me because the difference between single and double precision. I am learning about GPUS and GPGPUS, so i don't know very much about it.
In the second page of this pdf there is a specs table. NVIDIA-Tesla-Kepler-Family-Datasheet.pdf