On 18 December 2010 16:22, Jan Martin <janmar...@diy-streetview.org> wrote: > Bruno, > > care to estimate what kind of speed improvement optimizing the code would be > good for? > What would it need to get it done? > Who is qualified to do it? > > Jan > > >
I think it would be quite difficult. I remeber I looked at the nona code quite some time ago (bit it didn't really change since that time). Most of the code is generated at compile time from templates so sometimes it's a bit difficult to really understand what it does and especially how to optimize it. But I guess that a big slowdown is caused by vigra. Yeah, it allows to write completelly generic code like the nona code is but for a price. I know it from my experiments with hugin deghosting. Vigra's types are due to extensive polymorphism usage slow, even the simple ones like RGBsomethingsomething (I had too much vine to remeber that) or vector types like tinyvector. Also the reason of the slowdown is operator overloading. As I said, it allows you to write generic code but at a price. For example you can do things like a + b and it translates to a + b for one component data (eg. grayscale image) or (a[0] + b[0], a[1] + b[1], a[2] + b[2]) for RGB or Lab or whatever type which is a 3-component vector. The problem is code generated by the compiler when you add more together. For example a * b + c is, for three component data, implemented as somethinglike for (i=0; i <3; i++) tmpres[i] = a[i] + b[i] for (i = 0; i < 3; i++) res[i] = tmpres[i] + c[i] You can see that there these loops can be shrinked to one, but compiler won't do this. But there are some possibilities how to make compiler to make it in one loop but it's a black magic. If you implement all this manually (ie. you implement different code for vector types and scalar types) you can gain quite some speed but I wouldn't like to mutilate nona - this code is just too sexy. ciao, Lukas -- You received this message because you are subscribed to the Google Groups "Hugin and other free panoramic software" group. A list of frequently asked questions is available at: http://wiki.panotools.org/Hugin_FAQ To post to this group, send email to hugin-ptx@googlegroups.com To unsubscribe from this group, send email to hugin-ptx+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/hugin-ptx
