Hi Richard, Sorry to reply so late about this thread but I was away for few weeks.
> I'm trying to make my transform go fast. I've got a 1920x1080 > RGB image being transformed from sRGB to the display profile. Ok, sounds very similar to what I have to do in my application. (I also had to manage premultiplied alpha, but just ignore this in my source) I'm not a lcms expert, so I simply optimized the code path (involved by the transform that my application always uses) by unrolling some critic loops. In other words, I made the code less generic but it is several times faster for my particular need. Warning : this is not suitable for everyone & I consider my modification as a dirty hack but it may be of any help to you... Note that only the TYPE_BGRA_8 format has been optimized (normal transformation + soft proofing transform). If you are using another format, you'll need to modify slightly the source to get the same performances, otherwise you'll see no difference with legacy lcms 2.4. I made a little bench to test to improvements (done on my Core2Duo). Here are the result : - littleCMS legacy code : 92.12 CPU Cycle per pixel transformed - littleCMS hacked : 27.75 CPU Cycle per pixel transformed So I get a x 3.3 boost. I also sliced the image and ran several thread, thanks to Qt threading model. Final improvement was ~ X3.4 with 4 physical CPU (I guess you could get a x1.8 boost for 2 physical CPU). As overall performances were ~ X10, I stopped to dig further and use this code daily. Note that I also rewrote the critic loop with SSE4 assembly code (just for fun). I found no real improvement because most of the work is about memory exchange... So I kept the basic C code... Modified code can be downloaded here : http://sebastienleon.com/info/littleCMS/littleCMS_PreMulAlphaHack.zip (as you may not use premultiplied alpha support, I suggest you to undefine the flag I added: CMS_PREMUL_ALPHA_SUPPORT) Hopes it could help you... (you can use the code I added without any restrictions). Best regards Sebastien Hughes wrote: > Hi all, > > I'm trying to make my transform go fast. I've got a 1920x1080 RGB > image being transformed from sRGB to the display profile. I've got a > quad core processor on my development box, no shaders or GPU, and I'm > trying to do the transform as quickly as possible. > > I figured the fastest way to do this would be to set up a threadpool > with max_threads = 4. Then I have a few choices: > > * pop a thread from the pool for every line of the image, creating > local state with p_in, p_out, width and stride > * pop a thread from the pool for every n lines of the image, creating > local state with p_in, p_out, width, stride and rows_to_process (where > n = height / max_threads) > > I figured 4 threads should be ~4x faster than using 1 thread (in the > second case we should only have 4 threads, so not much overhead), but > no matter the value of max_threads or 'n' I can only achieve a ~1.9x > speed-up. I've tried with and without cmsFLAGS_NOCACHE. Any pointers > very welcome. > > Thanks, > > Richard ------------------------------------------------------------------------------ Introducing AppDynamics Lite, a free troubleshooting tool for Java/.NET Get 100% visibility into your production application - at no cost. Code-level diagnostics for performance bottlenecks with <2% overhead Download for free and get started troubleshooting in minutes. http://p.sf.net/sfu/appdyn_d2d_ap1 _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
