Source code for sympy.utilities.memoization

from __future__ import print_function, division

from sympy.core.decorators import wraps
from sympy.core.compatibility import xrange

[docs]def recurrence_memo(initial): """ Memo decorator for sequences defined by recurrence See usage examples e.g. in the specfun/combinatorial module """ cache = initial def decorator(f): @wraps(f) def g(n): L = len(cache) if n <= L - 1: return cache[n] for i in xrange(L, n + 1): cache.append(f(i, cache)) return cache[-1] return g return decorator
[docs]def assoc_recurrence_memo(base_seq): """ Memo decorator for associated sequences defined by recurrence starting from base base_seq(n) -- callable to get base sequence elements XXX works only for Pn0 = base_seq(0) cases XXX works only for m <= n cases """ cache = [] def decorator(f): @wraps(f) def g(n, m): L = len(cache) if n < L: return cache[n][m] for i in xrange(L, n + 1): # get base sequence F_i0 = base_seq(i) F_i_cache = [F_i0] cache.append(F_i_cache) # XXX only works for m <= n cases # generate assoc sequence for j in xrange(1, i + 1): F_ij = f(i, j, cache) F_i_cache.append(F_ij) return cache[n][m] return g return decorator