Thanks Terry! Of course, speed is not my main concern at this point and I'm more worried about precision...would you have some input on this discussion? :)
Jon On Mon, Mar 7, 2011 at 2:35 PM, Terry Reedy <tjre...@udel.edu> wrote: > On 3/7/2011 1:59 PM, Jon Herman wrote: > >> And for the sake of completeness, the derivative function I am calling >> from my integrator (this is the 3 body problem in astrodynamics): >> >> def F(mu, X, ti): >> >> r1= pow((pow(X[0]+mu,2)+pow(X[1],2)+pow(X[2],2)),0.5) >> > > x0 = X[0]; x1 = X[1]; x2 = X[2] > r1 = sqrt((x0+mu)**2) + x1*x1 + x2*x2) > etc... > might be faster. Certainly, repeated lookups of pow is slow > and above is easier to read. > > r2= pow((pow(X[0]+mu-1,2)+pow(X[1],2)+pow(X[2],2)),0.5) >> >> Ax= X[0]+2*X[4]-(1-mu)*(X[0]+mu)/r1**3-mu*(X[0]-(1-mu))/r2**3 >> Ay= X[1]-2*X[3]-(1-mu)*X[1]/r1**3-mu*X[1]/r2**3 >> Az= -(1-mu)*X[2]/r1**3-mu*X[2]/r2**3 >> >> XDelta=array([X[3], X[4], X[5], Ax, Ay, Az]) >> >> return XDelta >> \ >> > > > -- > Terry Jan Reedy > > -- > http://mail.python.org/mailman/listinfo/python-list >
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