[Haskell-beginners] Performance problem with Haskell/OpenGL/GLFW

Hollister Herhold hollister at fafoh.com
Sun Mar 10 23:27:56 CET 2013

I guess running X11 forces use of the NVidia chip. Interesting. 


On Mar 10, 2013, at 5:23 PM, Jesper Särnesjö <sarnesjo at gmail.com> wrote:

> On Mon, Mar 11, 2013 at 7:17 AM, Hollister Herhold <hollister at fafoh.com> wrote:
>> Okay, I think I just figured this out. Well, HOW to get it working with the
>> accelerated renderer.
>> I was wondering a simple way to check renderer info so I ran glxinfo. This
>> (automatically) fired up X11, and then on a hunch I re-ran Test2 with X11
>> running and got this:
>> hhmacbook:~/Development/haskell/OpenGL:57> ./Test2
>> hardware
>> (2,7,7)
>> (3,2,0)
>> hhmacbook:~/Development/haskell/OpenGL:58>
>> AH HA! I then quit X11 and re-ran Test2, and got this:
>> hhmacbook:~/Development/haskell/OpenGL:58> ./Test2
>> software
>> (2,7,7)
>> (3,2,0)
>> hhmacbook:~/Development/haskell/OpenGL:59>
>> SO- If you want the accelerated renderer, you need to have X11 running.
>> Now, I have no idea WHY this is the case, but there you go.
>> Hope this helps.
> This lead me down an interesting path.
> First, I should explain that my machine, like most newish Macs, has
> two graphics cards. In my case, a discrete Nvidia GeForce GT 330M, and
> an integrated Intel chip. The former is better, but the latter uses
> less power, and the system is supposed to switch between them
> automatically.
> I used gfxCardStatus [1] to show which card was in use. When I ran
> test2.c, the system briefly switched to the discrete card. However,
> when I ran Test2.hs, the system kept using the integrated chip the
> whole time. Presumably, the Intel chip lacks a hardware implementation
> of OpenGL 3.2, which causes the system to fall back to a software
> renderer. I then used gfxCardStatus to force the system to *always*
> use the discrete card and - boom! - this time Test2.hs received a
> hardware renderer!
> So it seems that the problem is a) Mac OS X-specific, or possibly
> specific to systems with multiple graphics cards, b) related to
> triggering the *switch* to the better graphics card. I don't yet
> understand why the C program triggers a switch, while the Haskell
> program does not, but I'll keep investigating.
> Thank you all very much for your help!
> -- 
> Jesper Särnesjö
> http://jesper.sarnesjo.org/
> [1] http://gfx.io
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