def gen_func(u, v):
'''R(v) = a + b * R(u)'''
# cache layer
try:
a, b = conn.execute('SELECT a, b FROM core_func WHERE id = %d' % (u * (N_USERS + 1) + v)).fetchone()
return lambda x: a + b * x
except:
pass
# unsuccessful hit
I = corate(u, v)
ru = get_ratings(u, I)
rv = get_ratings(v, I)
return _gen_func(ru, rv)
def cache(init = False):
'''caching function parameters -- a and b in R(v) = a + b * R(u)'''
if init:
conn.execute('DELETE FROM core_func')
x = conn.execute('SELECT MAX(id) FROM core_func').fetchone()[0] / (N_USERS + 1)
for i in range(x + 1, N_USERS + 1):
for j in range(1, N_USERS + 1):
try:
I = corate(i, j)
ru, rv = array(get_ratings(i, I)), array(get_ratings(j, I))
fp = lambda x, p: p[0] + p[1] * x
e = lambda p, y, x: abs(fp(x, p) - y).sum()
p = fmin(e, array([0, 1]), args = (rv, ru), maxiter = 10000, maxfun = 10000, disp = 0)
a, b = p[0], p[1]
conn.execute('INSERT INTO core_func VALUES(%d, %lf, %lf)' % (i * (N_USERS + 1) + j, a, b))
except sqlite3.IntegrityError:
print 'chongfu!'
print i
conn.commit()