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  [Solved] Simple Question  (Read 1563 times)
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Offline Vladiedoo
« Posted 2012-06-12 00:30:25 »

Hi, I want to crunch some numbers with Java and I'm going to be testing Crit Chance (a %chance on hit that you'll deal x times more damage).

Does the code below correctly simulate someone attacking 1 million times with 100 damage and a 10% chance to crit for 300% damage?
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//this is a method's body
Random dice = new Random();
double total = 0;
double damage = 100;
for(double i = 1; i < 1000000; i++){
   if(dice.nextInt(100) + 1 < 10){
      total += damage * 3;
   }else{
      total += damage;
   }
}
return total;
Offline sproingie

JGO Kernel


Medals: 202



« Reply #1 - Posted 2012-06-12 00:37:08 »

Looks right to me.  Just split out the meat of the loop into a method and it'll even look obviously right.
 
Rule #1 of simulation: do it once, repeat it 999999 more times.

Rule #1000000 of simulation: do it once, repeat it 0 more times.
Offline Sickan
« Reply #2 - Posted 2012-06-12 07:14:33 »

Why do you use doubles for your for loops? I'm just generally curious why.
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Offline Riven
Administrator

« JGO Overlord »


Medals: 1220
Projects: 4
Exp: 16 years


Hand over your head.


« Reply #3 - Posted 2012-06-12 07:27:43 »

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if(dice.nextInt(100) + 1 < 10){

dice.nextInt(100) gives you 100 distinct values: 0..99, you turned that into 1..100.

If you count the number of values that are smaller than 10, you get: 1,2,3,4,5,6,7,8,9 (nine numbers)

So your code actually calculates the results for 9/100 (9%) chance to cause 300% damage.

Just remove the +1 and you're fine.

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Offline Vladiedoo
« Reply #4 - Posted 2012-06-12 14:13:52 »

Sproingie: Thanks for the feedback x).

Sickan: I use double's because at times I'd want to calculate 175% crit and that number would get rounded as an int.

Riven: Thanks! That's the part of the code that was bugging me.
Offline ReBirth
« Reply #5 - Posted 2012-06-12 14:28:13 »

No, he did mean why you use double for 'i', which is unused inside the loop.

Offline Vladiedoo
« Reply #6 - Posted 2012-06-12 14:33:35 »

Ah valid point, I'll switch that to int then. I originally had my code all in int and did a Ctrl+f replace all int with double and forgot to check it over after doing that, thanks.
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