On Sat, 1 Sep 2007, Chris Jones wrote: > > Another poster mentioned that pentiums > > have hardware instructions for trig functions. > > If you are using them, there isn't much hope for speed up. > > Out of interest, whats needs to be done to use these, some gcc flag ? My gcc won't use them unless it knows that your version of the cpu has them. You probably need to add a flag that tells gcc exactly what cpu you have. You might also need -ffast-math . If all else fails, there is always inline assembly. > profiling suggests that atan2(x,y) is taking ~ 50% of some method speed. Yes, > the methods is already fast, but still is this reasonable if hardware > instructions are being used. Is there some way I can check to see exactly > what is used ? objdump -S galadriel.elf > galadriel.lss Will produce an disassembly listing intermixed with source. > > These formulas will probably not be useful unless > > you know in advance the ranges of their arguments. > > Yes, I considered coding up my own methods along this line, but figured > getting it correct was not a small amount of effort, and was hoping to find > some project that had done it for me. How much precision do you need? On what? Why? At least one person wrote a book on implementing the C standard library. It would probably be a better resource than Numerical Recipes. -- Mike hennebry@xxxxxxxxxxxxxxxxxxxxx "Horse guts never lie." -- Cherek Bear-Shoulders
