jyr <jyr2...@googlemail.com> writes: > The thought has occured to me that one could use the index functions > for the 3j, 6j, and Gaunt coefficients for a much simpler storage > scheme in python by using the index as a key for a dictionary of > stored symbols. I could then extend the above published routines with > an optional 'remember' keyword that would store them from one call to > the next. > However, I am not sure how much memory dictionaries consume in python > and whether this is efficient. At the end of the day for any realistic > calculation you are usually talking about millions of them.
In my experience doing extremely large-scale computations using 10^10 or more 6j symbols, it is faster to evaluate a 6j symbol than to look it up in a hash table. On the other hand, if you repeatedly need sequences of 6j symbols with one argument varying, it does pay off to store arrays of 6j symbols in a hash table with the key being the 5 fixed arguments. That is all in C using floating point, so it may be worthwhile using a hash table if you want exact rational results. By the way, I have a C library, written with Igor Khavkine, that computes 3j, 6j, 10j and other networks using your choice of exact rational or floating point arithmetic. It also does the q-deformed calculations, either for fixed complex q (returning a complex) or for symbolic q (returning an exact rational function of q). It is optimized for speed and even has a python interface. The bad news is that it is complicated to build, not well-documented, and not really in a state for others to use. So it would be great if Jens' library could be included in sage! Dan PS: I'm currently working on using sage to evaluate 3j and 6j symbols for SU(n) for n > 2 (the above being the n=2 case). I'll report to the list if I come up with something appropriate for inclusion in sage. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to sage-devel-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
