## LuxMark v2.0 released

Show-off, reference material & tools.
Posts: 206
Joined: Fri Dec 02, 2011 8:00 am

### LuxMark v2.0 released

Introduction

After a year from the release, LuxMark v1.0 has been widely used as OpenCL benchmark by AnandTech, Tom's Hardware, Vr-zone and other sites. AMD has used LuxMark as one of the 5 GPU computing benchmarks to present the new HD7970.

LuxMark v2.0 includes SLG2 as rendering engine with Metropolis Light Transport, Multiple Importance Sampling, Image reconstruction done on the GPU, support for multiple OpenCL platforms (i.e. Nvidia users can use Intel or AMD CPU device) and many more new features. The new features rise the complexity of the benchmark of nearly one order of magnitude and it should be able to put some serious stress on the new generation of GPUs. The capability to submit results to a centralise WEB database looks like the most interesting new feature of LuxMark v2.0: http://www.luxrender.net/luxmark

Features

* Open source
* 100% OpenCL
* Cross platform (Linux, MacOS, Windows, etc.)
* Complex/real world code used as GPU computing benchmark
* Support for OpenCL GPUs-only, OpenCL CPUs+GPUs, OpenCL CPUs-only and native CPU-only benchmarking
* Support for Interactive mode
* Easy to run
* Multiple scenes usable as benchmarks

New in LuxMark v2.0:

* Totally new rendering engine based on SLG2 with Metropolis Light Transport, Multiple Importance Sampling, Image reconstruction done on the GPU, ecc;
* Multi-platform OpenCL support;
* 2 new benchmark scenes, for a total of 3 benchmarks with a raising complexity (~200,000, ~500,000, ~2,000,000 triangles);
* Run the benchmark only on the OpenCL devices you selected on the device panel;
* Added the possibility to submit the scored result to a centralised result database: http://www.luxrender.net/luxmark;

LuxMark is part of LuxRays source repository and is release under GPL license. The sources are available at http://src.luxrender.net/luxrays

Result Database http://www.luxrender.net/luxmark

If you have a valid LuxRender forum account, you can submit your results to the LuxMark result database: http://www.luxrender.net/luxmark. The database offers online real-time browsing, searching, average results, top 20s and many more features.

dbz
Posts: 46
Joined: Wed Jan 11, 2012 10:16 pm
Location: the Netherlands

### Re: LuxMark v2.0 released

I noticed something when looking at the Luxmark benchmarks, when comparing single cpu vs single gpu results, the gpu is not really that much faster than the cpu.

For example, high end cpu i7-2600k vs high end gpu gtx 570 (both released within 3 months of each other)

simple benchmark cpu 3966, gpu 5867 k samples/s
medium benchmark cpu 512 , gpu 836
complex benchmark cpu 328, gpu 393

The gpu is faster, but not that much faster and nowhere near 10x. And actually, Luxmark looks like it has been written for the gpu(but I may be wrong here). So, an optimized cpu version could do even better.

Posts: 206
Joined: Fri Dec 02, 2011 8:00 am

### Re: LuxMark v2.0 released

dbz wrote:The gpu is faster, but not that much faster and nowhere near 10x. And actually, Luxmark looks like it has been written for the gpu(but I may be wrong here). So, an optimized cpu version could do even better.
Where is written that the GPU must be 10 times faster than a comparable CPU ?

Did you noticed also the other pattern ? More complex the scene is and better the CPU perform when compared with the GPU.

On other side, if you start to factor the cost of cutting in half your rendering time, GPUs will look more interesting. It costs a lot less to buy one more 570GTX than another PC with a i7-2600k.

Side note: you are probably using latest NVIDIA OpenCL 1.1 compliant driver and it has a well known problem with about any OpenCL application (i.e. it is about a 50% slower than previous OpenCL 1.0 driver). There is a long thread about this problem in NVIDIA OpenCL forum but the vendor has not yet provided an explanation or a solution to the problem (at least I'm not aware of anyone but roll back to previous driver).

dbz
Posts: 46
Joined: Wed Jan 11, 2012 10:16 pm
Location: the Netherlands

### Re: LuxMark v2.0 released

Dade wrote: Where is written that the GPU must be 10 times faster than a comparable CPU ?
Well, there is a certain gpu manufacturer that used to claim 10 - 100 times speedups over the cpu when implementing your algorithm in CUDA
On other side, if you start to factor the cost of cutting in half your rendering time, GPUs will look more interesting. It costs a lot less to buy one more 570GTX than another PC with a i7-2600k.
That is certainly true however when looking at performance per watt it seems that the cpu is still the winner. An i7-2600k takes about 100 Watts under load while a gtx 570 takes around 200 Watts while the gpu is less than twice as fast.

The benefit of the gpu seems to lie more in the possibility to add several graphics cards in one system than anything else.
Side note: you are probably using latest NVIDIA OpenCL 1.1 compliant driver and it has a well known problem with about any OpenCL application (i.e. it is about a 50% slower than previous OpenCL 1.0 driver). There is a long thread about this problem in NVIDIA OpenCL forum but the vendor has not yet provided an explanation or a solution to the problem (at least I'm not aware of anyone but roll back to previous driver).
I guess the stability of the drivers will always remain a problem for doing anything on the gpu. Also, people on the ATI OpenCL forum complain a lot ...

Posts: 206
Joined: Fri Dec 02, 2011 8:00 am

### Re: LuxMark v2.0 released

dbz wrote:
Dade wrote: Where is written that the GPU must be 10 times faster than a comparable CPU ?
Well, there is a certain gpu manufacturer that used to claim 10 - 100 times speedups over the cpu when implementing your algorithm in CUDA
Hehe, I know but I have never observed that kind of speed-up in our field. In my opinion, smaller is your "Render farm" and more interesting the GPUs are (and vice versa: larger it is and less interesting they are).

beason
Posts: 52
Joined: Sat Dec 10, 2011 1:58 am
Location: Los Angeles, CA

### Re: LuxMark v2.0 released

FWIW I tried to run the linux binary on SuSE 11.1 but I got some linking errors:

Code: Select all

./luxmark-linux64: /usr/lib64/libOpenCL.so.1: no version information available (required by ./luxmark-linux64)
./luxmark-linux64: /usr/lib64/libstdc++.so.6: version GLIBCXX_3.4.11' not found (required by ./luxmark-linux64)

Guess I'll have to compile from source.

dbz, thanks for sharing your results, they are very interesting!

Posts: 206
Joined: Fri Dec 02, 2011 8:00 am

### Re: LuxMark v2.0 released

beason wrote: FWIW I tried to run the linux binary on SuSE 11.1 but I got some linking errors:

Code: Select all

./luxmark-linux64: /usr/lib64/libOpenCL.so.1: no version information available (required by ./luxmark-linux64)

Guess I'll have to compile from source.
Yup, the linux 64bit binaries were compiled on an Ubuntu and I guess SuSE uses a different LibC version.

khalidsalman
Posts: 8
Joined: Thu Dec 22, 2011 10:56 pm

### Re: LuxMark v2.0 released

I remember you mentioned sometime ago that SLG(or luxrender?) relies on GPU for finding intersections only. Is that the case? does luxmark do the same or do you run the whole pipeline through OpenCL?

Thanks.

Posts: 206
Joined: Fri Dec 02, 2011 8:00 am

### Re: LuxMark v2.0 released

khalidsalman wrote: I remember you mentioned sometime ago that SLG(or luxrender?) relies on GPU for finding intersections only. Is that the case? does luxmark do the same or do you run the whole pipeline through OpenCL?
The first versions of SLG (v1.x) were used to test hybrid rendering and later also a 100% OpenCL render mode was added (i.e. whole pipeline was written in OpenCL). The 100% OpenCL render mode was then used to write LuxMark v1.0.

SLG v2.x includes only 100% OpenCL render mode that resembles classic PBRT/LuxRender pipeline (i.e. sampler+surface integrator+image reconstruction from samples with filter).

LuxMark v2.0 is based on SLG2 so it runs all the pipeline through OpenCL.

khalidsalman
Posts: 8
Joined: Thu Dec 22, 2011 10:56 pm

### Re: LuxMark v2.0 released

I see, thanks for the explanation.