Today’s Graphics Hardware is Too Hard

Tim Sweeny recently gave a keynote at High Performance Graphics 2009 titled "The End of the GPU Roadmap" (slides). Tim is CEO and founder of Epic Games, producers of over 30 games including Gears of War, as well as the Unreal game engine used in 100s of games. There are lots of really interesting points in that 74-slide presentation, but my biggest keeper is slide 71:

[begin quote]

Lessons learned: Today's hardware is too hard!

• If it costs X (time, money, pain) to develop an efficient single-threaded algorithm, then…
  
  • Multithreaded version costs 2X
    
  • PlayStation 3 Cell version costs 5X
    
  • Current "GPGPU" version costs: 10X or more
    
• Over 2X is uneconomical for most software companies!
  
• This is an argument against:
  
  • Hardware that requires difficult programming techniques
    
  • Non-unified memory architectures
    
  • Limited "GPGPU" programming models
    

[end quote]

Judging from the prior slides, by '"GPGPU"' Tim apparently means the DirectX 10 pipeline with programmable shaders.

I'm not sure what else to make of this beyond rehashing Tim's words, and I'd rather point you to his slides than start doing that. The overall tenor somewhat echoes comments I made in one of my first posts; it continues to be the most hit-on page of this blog, so I must have said something useful there.

I will note, though, that Tim's estimates of effort are based on very extensive experience – with game programming. For low-ish levels of parallelism, like 4 or 8, multithreading adds zero cost to typical commercial applications already running under a competent transaction monitor. It just works, since they're already at that level of software multithreading for other reasons (like achieving overlap with IO waits). Of course, that's not at all universally true for commercial applications, particularly for high levels of parallelism, no matter how much cloud evangelists talk about elasticity.

Once again, thanks to my friend who is expert at finding things like this slide set (it's not on the conference web site) and doesn't want his name mentioned.

Short post this time.