since you only need to calculate the sine or cosine of a single value (not an array of values) I would recommend using the sine and cosine function of the python standard math library as it is a full order of magnitude faster. (at least on my core 2 windows vista box)
i.e. import math as m m.sin m.cos etc.... again, this is microoptimization.... a difference of 10^-5s per call vs 10^-6s per call numpy vs math Chris On Wed, Mar 4, 2009 at 12:11 AM, <josef.p...@gmail.com> wrote: > On Tue, Mar 3, 2009 at 11:41 PM, Jonathan Taylor > <jonathan.tay...@utoronto.ca> wrote: > > Thanks, All these things make sense and I should have known to > > calculate the sins and cosines up front. I managed a few more > > "tricks" and knocked off 40% of the computation time: > > > > def rotation(theta, R = np.zeros((3,3))): > > cx,cy,cz = np.cos(theta) > > sx,sy,sz = np.sin(theta) > > R.flat = (cx*cz - sx*cy*sz, cx*sz + sx*cy*cz, sx*sy, > > -sx*cz - cx*cy*sz, -sx*sz + cx*cy*cz, > > cx*sy, sy*sz, -sy*cz, cy) > > return R > > > > Pretty evil looking ;) but still wouldn't mind somehow getting it faster. > > One of the usual recommendation on the python list is also to load > functions into the local scope to avoid the lookup in the module. > > e.g. npcos = np.cos > or I think the usual: `from numpy import cos, sin, zeros` should be > better for speed > > also you still have a few duplicate multiplications, e.g. cx*cz, cx*sz, ..? > but this looks already like micro optimization. > > Josef > _______________________________________________ > Numpy-discussion mailing list > Numpy-discussion@scipy.org > http://projects.scipy.org/mailman/listinfo/numpy-discussion >
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