[Bf-committers] massive cuda speed improvements with Cuda 5.0/5.5

[Jürgen Herrmann]

Hi there, 

 

I did some tests with cuda 5.0 and 5.5 today and changed the nvcc
optimization flags for cycles_kernel_cuda.

 

I found out the following: 

 

-          “--opencc-options “ is deprecated for sm_20 and up and should be
removed from compiler options

-          Stating “-O3” and “—use_fast_math” as nvcc options brings massive
speedup on my system (more below)

-          We shouldn’t complain about new cuda toolsets that are slow, we
should find a solution as we can’t use old software forever


 

To the speedups:

 

Example 1: 

system: i7-3820 @ 3.60GHz, GeForce GTK 660

 

Blender (cycles_cuda_kernel) compiled with standard settings:

Mike_pan file took 02:06.60 to render

 

Blender (cycles_cuda_kernel) compiled with –O3 –use-fast-math:

Mike_pan took 01:39:93

 

There is no optical difference in the render results:

 

Image1: http://www.pasteall.org/pic/52757

Image2: http://www.pasteall.org/pic/52758

 

I bet there’s more potential in there.

 

/Jürgen