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Damage prediction: round very close slow probabilities to 0 or 1

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In the case in bug #3321, damage prediction code somehow receives a
combatant whose probability to be slowed is very close to one of those
values but not quite it. I couldn't figure out how it's possible because
only damage prediction code itself is supposed to emit slow probabilities,
and it's not producing such a probability in this case.

Without more information, I'm simply fixing the bug by force. If the
probability is in the problematic area, we simply round it to 0 or 1. This
way such probabilities are impossible later on when we try to scale the HP
distributions so that they add to 1.

Fixes #3321.
This commit is contained in:
Jyrki Vesterinen 2018-07-06 22:52:34 +03:00
parent a7f3294a24
commit ec54b761bc
1 changed files with 14 additions and 0 deletions
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14
src/attack_prediction.cpp
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@ -1820,6 +1820,16 @@ double calculate_probability_of_debuff(double initial_prob, bool enemy_gives, do
return prob_debuff;
}
// Rounds a probability that's extremely close to 0 or 1 to exactly 0 or 1.
void round_prob_if_close_to_sure(double& prob)
{
if(prob < 1.0e-9) {
prob = 0.0;
} else if(prob > 1.0 - 1.0e-9) {
prob = 1.0;
}
}
/**
* Returns the smallest HP we could possibly have based on the provided
* hit point distribution.
@ -2309,6 +2319,10 @@ void combatant::fight(combatant& opponent, bool levelup_considered)
double self_already_dead = hp_dist[0];
double opp_already_dead = opponent.hp_dist[0];
// If incoming slow probabilities are extremely close to 0 or 1, round them to exactly 0 or 1 (bug #3321)
round_prob_if_close_to_sure(slowed);
round_prob_if_close_to_sure(opponent.slowed);
// If we've fought before and we have swarm, we might have to split the
// calculation by number of attacks.
const std::vector<combat_slice> split = split_summary(u_, summary);