wired calculation I don't get it 30-30 = 1.907349E-06

Question

IF I use this:

 float TempPCF = CreateFloor.PerCreateFake*100f;
 float TempPSF = CreateFloor.PerStopFake*100f;
 int TempPCFi = (int)TempPCF;
 int TempPSFi = (int)TempPSF;
 Debug.Log(""+TempPCFi);
 Debug.Log(""+TempPSFi);
 Debug.Log(""+TempPCF + " " + TempPSF);

I get resault

 50
 30
 50 30

I like this resault

BUT arghhh with this:

 float TempPCF = CreateFloor.PerCreateFake*100f;
 float TempPSF = CreateFloor.PerStopFake*100f;
 int TempPCFi = (int)TempPCF;
 int TempPSFi = (int)TempPSF;
     TempPCF -= TempPCFi;
     TempPSF -= TempPSFi;
 Debug.Log(""+TempPCFi);
 Debug.Log(""+TempPSFi);
 Debug.Log(""+TempPCF + " " + TempPSF);

I get resault:

 50
 30
 0 1.907349E-06

ARGHHH HOW DA can he calculate 30-30 = 1.907349E-06

and I don't belive 2 static have any kind of problems here as I've assign 2 temporary variables just for them

Answer 1

Best Answer

Answer by Chronos-L · Mar 19, 2013 at 08:02 AM

1.907349E-06 is equal to 1.907349 x 10 ^ -6, which is equivalent to 0.000001907349 and very close to 0. It is caused by floating point imprecision. Unity even has a Mathf.Approximately to deal with checking the equality between 2 float.

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sdgd · Mar 19, 2013 at 08:08 AM 0

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hey where did 1 answer go I have puted both thumbs up as they were both pretty much same

and thanks I thought it's 1.9 not 0.000019

it makes me breath more easily as now I can check if it's 0.1 bigger not 0

Answer 2

Answer by xt-xylophone · Mar 19, 2013 at 08:03 AM

I think sometimes floats that say they are whole numbers are actually really close and not exact. It's kinda like a rounding error. In your case it's an error of only 0.000001907349

Casting won't help with this. Maybe try a rounding function before you do the maths?

Or if on the future you want to check if 2 floats are equal, try checking if the difference is less than a reeeaally small number instead of ==

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Fattie · Mar 19, 2013 at 08:08 AM 2

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Mathf.Approximately exists for that purpose.

xt-xylophone · Mar 19, 2013 at 09:41 AM 0

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^ awesome, didn't know that one!

wired calculation I don't get it 30-30 = 1.907349E-06

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