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134 lines
4.8 KiB
134 lines
4.8 KiB
#!/usr/bin/env python
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# Calculate probability of getting at least one of a monster part from one
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# line in the quest rewards. Also calculates expected value of part
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# counts (N), and probabilities of getting a certain number of rewards (C).
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#
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# usage: mhprob.py reward_percent fixed_rewards gaurenteed_rewards \
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# [extend_percent]
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#
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# reward_percent - chance of getting the monster part in %
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# fixed_rewards - number of rewards in the reward list with 100% chance and
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# are not the item you are looking for. Takes away from
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# the total possible draw attempts for what you want.
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# Default 1 which is typical for line A in many quests.
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# gaurenteed_rewards - minimum number of quest rewards in the line,
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# including any fixed rewards. In Tri (see link
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# below) this is 3 for line A and 1 for line B.
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# Defaults to 3.
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# extend_percent - chance of getting one more reward in the line in %,
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# default 69
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#
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# You can use http://kiranico.com to get reward percent and fixed rewards
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# values.
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#
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# For extend percent, use the default unless you have the Lucky Cat or
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# Ultra Lucky Cat food skills or Good Luck or Great Luck armor skills:
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#
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# normal extra reward %: 69
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# good luck extra reward %: 81
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# great luck extra %: 90
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#
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# Can also be used to calculate chance of getting a part from carving,
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# using extend_percent=0, fixed_rewards=0, and gaurenteed_rewards=3 (or
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# 4 for monsters with 4 carves).
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#
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# Source:
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# http://www.gamefaqs.com/wii/943655-monster-hunter-tri/faqs/60448
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# Not sure if there are differences in 3U or 4U.
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#
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# Example Plain dangerous in 3U, has 2 fixed rewards in A, one in B, hardhorns
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# are 5% both A and B:
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# A: ./mhprop.py 5 2 3 69
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# B: ./mhprop.py 5 1 1 69
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# For great luck, replace 69 with 90
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import sys
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def _quest_reward_p(reward_percent, reward_count):
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"""
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Propability of getting at least one item from @reward_count draws
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with a @reward_percent chance.
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"""
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fail_percent = (100 - reward_percent)
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return 1.0 - (fail_percent / 100.0)**reward_count
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def _reward_count_p(reward_count, min_rewards, max_rewards, extend_percent):
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"""
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Probability of getting a certain number of rewards for a given chance
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@extend_percent of getting one more drop.
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"""
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if reward_count == min_rewards:
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return (100 - extend_percent) / 100.0
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p = 1.0
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extend_p = extend_percent / 100.0
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stop_p = 1.0 - extend_p
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for i in xrange(min_rewards+1, reward_count+1):
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p *= extend_p
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if reward_count < max_rewards:
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p *= stop_p
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return p
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def quest_reward_p(reward_percent, min_rewards, max_rewards, extend_percent=69):
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"""
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Probability of getting at least one of the item, given the item has
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@reward_percent chance, @min_rewards minimum number of attempts,
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@max_rewards max attempts, and @extend_percent chance of getting each
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extra attempt.
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"""
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p = 0.0
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for reward_count in xrange(min_rewards, max_rewards + 1):
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p += (_reward_count_p(reward_count, min_rewards, max_rewards,
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extend_percent)
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* _quest_reward_p(reward_percent, reward_count))
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return p * 100
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if __name__ == '__main__':
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# in percent
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reward_percent = int(sys.argv[1])
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if len(sys.argv) > 2:
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fixed_rewards = int(sys.argv[2])
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else:
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fixed_rewards = 1
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if len(sys.argv) > 3:
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guarenteed_rewards = int(sys.argv[3])
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else:
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guarenteed_rewards = 3
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if len(sys.argv) > 4:
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extend_percent = int(sys.argv[4])
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else:
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extend_percent = 69
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min_rewards = guarenteed_rewards - fixed_rewards
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max_rewards = 8 - fixed_rewards
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if min_rewards < 0:
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print "Error: fixed_rewards (%d) must be less than or equal to " \
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"guaranteeed_rewards (%d)" % (fixed_rewards, guarenteed_rewards)
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sys.exit(1)
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total_p = 0.0
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expected_v = 0.0
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for reward_count in xrange(min_rewards, max_rewards + 1):
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p = _reward_count_p(reward_count, min_rewards, max_rewards,
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extend_percent)
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expected_v += p * reward_count
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# probability of getting @reward_count rewards that could be the
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# desired item
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print "P(C = %d) = %0.4f" % (reward_count, p)
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total_p += p
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# expected value for number of rewards that could be the desired item
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print "E(C) = %0.2f" % expected_v
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# math check, make sure all possibilities add up to 1, allowing for
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# some floating point precision loss.
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assert abs(total_p - 1.0) < .00001, "total = %f" % total_p
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p_at_least_one = quest_reward_p(reward_percent, min_rewards, max_rewards,
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extend_percent)
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expected = expected_v * reward_percent / 100.0
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print "P(N > 0) =", p_at_least_one
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print "E(N) =", expected
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