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

[Jürgen Herrmann]

Hi Dalai,

I tested 5.5 on a different system I don't have access to this machine right now, I'll deliver the complete benchmark results tomorrow.
I plan to compare on as many different configurations with 32 and 64 bit and different cuda versions.

This will take some time but I think it's worth it. ;)

/Jürgen

Am 03.06.2013 um 20:50 schrieb Dalai Felinto <dfelinto at gmail.com>:

> Hi Jurgen,
> 
> How does this times compare between CUDA 5.0 and 5.5?
> (is this a speedup from 5.5 but a slowdown in relation with 5.0? or
> it's an overall speed up ?)
> 
> --
> Dalai
> 
> 2013/6/3 Jürgen Herrmann <shadowrom at me.com>:
>> 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
>> 
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