On Mon, 2014-10-06 at 17:03 +0200, Erik Faye-Lund wrote: > On Fri, Sep 26, 2014 at 6:11 PM, Erik Faye-Lund <kusmab...@gmail.com> wrote: > > Our current atan()-approximation is pretty inaccurate at 1.0, so > > let's try to improve the situation by doing a direct approximation > > without going through atan. > > > > This new implementation uses an 11th degree polynomial to approximate > > atan in the [-1..1] range, and the following identitiy to reduce the > > entire range to [-1..1]: > > > > atan(x) = 0.5 * pi * sign(x) - atan(1.0 / x) > > > > This range-reduction idea is taken from the paper "Fast computation > > of Arctangent Functions for Embedded Applications: A Comparative > > Analysis" (Ukil et al. 2011). > > > > The polynomial that approximates atan(x) is: > > > > x * 0.9999793128310355 - x^3 * 0.3326756418091246 + > > x^5 * 0.1938924977115610 - x^7 * 0.1173503194786851 + > > x^9 * 0.0536813784310406 - x^11 * 0.0121323213173444 > > > > This polynomial was found with the following GNU Octave script: > > > > x = linspace(0, 1); > > y = atan(x); > > n = [1, 3, 5, 7, 9, 11]; > > format long; > > polyfitc(x, y, n) > > > > The polyfitc function is not built-in, but too long to include here. > > It can be downloaded from the following URL: > > > > http://www.mathworks.com/matlabcentral/fileexchange/47851-constraint-polynomial-fit/content/polyfitc.m > > > > This fixes the following piglit test: > > shaders/glsl-const-folding-01 > > > > Signed-off-by: Erik Faye-Lund <kusmab...@gmail.com> > > Reviewed-by: Ian Romanick <ian.d.roman...@intel.com> > > Ping?
Are you just looking for someone to commit this? > _______________________________________________ > mesa-dev mailing list > mesa-dev@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/mesa-dev _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
