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Markov: _retrieve_random_k2_for_value

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rather than getting all k2s for a value from the database, then walking
the list and picking one at random, pick one for a value at random via
a query

this simplifies the code, and is (usually) faster than the old way,
which has been removed. it would be even faster if it weren't for that
context_id stuff, but so it goes
This commit is contained in:
Brian S. Stephan 2013-02-08 01:15:32 -06:00
parent b5be0501de
commit 5a55227cf9
1 changed files with 32 additions and 30 deletions
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62
modules/Markov.py
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@ -375,9 +375,10 @@ class Markov(Module):
# work backwards
working_backwards = []
key_hits = self._retrieve_k2_for_value(seed_word, context_id)
if len(key_hits):
back_k2 = self._retrieve_random_k2_for_value(seed_word, context_id)
if back_k2:
found_word = seed_word
working_backwards.append(back_k2)
working_backwards.append(found_word)
self.log.debug("started working backwards with: {0:s}".format(found_word))
self.log.debug("working_backwards: {0:s}".format(" ".join(working_backwards)))
@ -389,28 +390,22 @@ class Markov(Module):
# some time is spent on better forward chains
max_back = random.randint(1, max_size/2) + random.randint(1, max_size/2)
self.log.debug("max_back: {0:d}".format(max_back))
while True:
key_hits = self._retrieve_k2_for_value(working_backwards[0], context_id)
if self.start2 in key_hits and len(working_backwards) > max_back:
self.log.debug("max_back exceeded, cleanly finishing")
while len(working_backwards) < max_back:
back_k2 = self._retrieve_random_k2_for_value(working_backwards[0], context_id)
if back_k2 == self.start2:
self.log.debug("random further back was start2, finishing")
gen_words += working_backwards
self.log.debug("gen_words: {0:s}".format(" ".join(gen_words)))
break
elif len(key_hits) == 0:
self.log.debug("no key_hits, finishing")
gen_words += working_backwards
self.log.debug("gen_words: {0:s}".format(" ".join(gen_words)))
break
elif len(filter(lambda a: a!= self.start2, key_hits)) == 0:
self.log.debug("only start2 in key_hits, finishing")
gen_words += working_backwards
self.log.debug("gen_words: {0:s}".format(" ".join(gen_words)))
break
else:
found_word = random.choice(filter(lambda a: a != self.start2, key_hits))
working_backwards.insert(0, found_word)
self.log.debug("added '{0:s}' to working_backwards".format(found_word))
elif back_k2:
working_backwards.insert(0, back_k2)
self.log.debug("added '{0:s}' to working_backwards".format(back_k2))
self.log.debug("working_backwards: {0:s}".format(" ".join(working_backwards)))
else:
self.log.debug("nothing (at all!?) further back, finishing")
gen_words += working_backwards
self.log.debug("gen_words: {0:s}".format(" ".join(gen_words)))
break
hit_word = seed_word
else:
@ -538,23 +533,30 @@ class Markov(Module):
raise
finally: cur.close()
def _retrieve_k2_for_value(self, v, context_id):
"""Get the value(s) for a given key (a pair of strings)."""
def _retrieve_random_k2_for_value(self, v, context_id):
"""Get one k2 for a given value."""
values = []
db = self.get_db()
try:
query = 'SELECT k2 FROM markov_chain WHERE v = %s AND context_id = %s'
query = '''
SELECT k2 FROM markov_chain AS r1
JOIN (
SELECT (RAND() * (SELECT MAX(id) FROM markov_chain)) AS id
) AS r2
WHERE r1.id >= r2.id
AND r1.v = %s
AND r1.context_id = %s
ORDER BY r1.id ASC
LIMIT 1
'''
cur = db.cursor(mdb.cursors.DictCursor)
cur.execute(query, (v, context_id))
results = cur.fetchall()
for result in results:
values.append(result['k2'])
return values
result = cur.fetchone()
if result:
return result['k2']
except mdb.Error as e:
self.log.error("database error in _retrieve_k2_for_value")
self.log.error("database error in _retrieve_random_k2_for_value")
self.log.exception(e)
raise
finally: cur.close()