float vs double on graphics hardware

Question

I\'ve been trying to find info on performance of using float vs double on graphics hardware. I\'ve found plenty of info on float vs double on CPUs, but such info is more scarce

Answer 1

Most GPUs don't support double floats at all. The support has been added very recently (this generation), and not everywhere:

• ATI:
  • HD5870 and HD5850 have it at decent speed (not as fast as single though)
  • HD5770 does not have it, despite being in the same generation as the HD5870.
• Nvidia:
  • GT200 based cards have double support, but at a double/single ratio that is very low. (8:1 ratio ?)
  • Fermi is supposed to have it at half speed of single... Whenever that ships.

For everything else, you just don't have double support.

So... You should definitely not use double if you don't need it.