RoundUp gives wrong value

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Hello All

C#

  I am trying to calculate  using RoundUp(). I am using the following code.

  Double per =(Double)Convert.ToDecimal((1.92* 100) / 2.2);
  Double p = RoundUp(per, 2);

 It is giving me a value of p =87.28
 while value of per is 87.27272722727277

What is the reason for this? Surely it should be returning a value of 87.27 right?

Please enlighten me. Thanks.

Posted 28-Nov-13 2:35am

ErBhati

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Comments

CPallini 28-Nov-13 8:40am

What is 'RoundUp()'? Do you defined it?

Karthik_Mahalingam 28-Nov-13 8:44am

post the code for RoundUP method

Sergey Alexandrovich Kryukov 28-Nov-13 11:27am

Why? Rounding is rarely needed and can be dangerous. Most people who ask about rounding in fact needs certain rounded string formatting for numeric values...
What is "RoundUp"?
—SA

4 solutions

Solution 1

If the purpose of the RoundUp() function is ... to round values UP ... then it looks like it's working correctly?

If you want your values simply rounded, either Up or Down, then have a look at the Round function:

C#

Math.Round(per, 2)

Posted 28-Nov-13 3:20am

hypermellow

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ErBhati 29-Nov-13 0:23am

thanks

Solution 3

Have a read of this, in particular Jon Skeets answer

http://stackoverflow.com/questions/977796/why-does-math-round2-5-return-2-instead-of-3-in-c[^]

and this MSDN

http://msdn.microsoft.com/en-us/library/wyk4d9cy.aspx[^]

They are saying that

Quote:

Return Value
Type: System.Double
The integer nearest a. If the fractional component of a is halfway between two integers, one of which is even and the other odd, then the even number is returned. Note that this method returns a Double instead of an integral type.

Posted 28-Nov-13 3:41am

Simon_Whale

Comments

Sergey Alexandrovich Kryukov 28-Nov-13 11:37am

This is not the case OP shows. It should be 87.27 in all possible rounding methods, but OP got 87.28. But we have no information on how OP got it. Who knows what "RoundUp" is? I would not bother to answer at all...

Rounding is not so trivial thing, odd/even rule is also can cause shift in distribution.

I always question if the rounding is needed at all. Usually, when inquirers ask for rounding, they don't really need it.

—SA

Simon_Whale 28-Nov-13 11:57am

Actually a good read is on stackoverflow (http://stackoverflow.com/questions/1584314/conversion-of-a-decimal-to-double-number-in-c-sharp-results-in-a-difference), there is a rounding issue converting a decimal into a double.

"For a conversion from decimal to float or double, the decimal value is rounded to the nearest double or float value. While this conversion may lose precision, it never causes an exception to be thrown."

so it would appear that the problem isn't the rounding by the type conversion from decimal to double.

Sergey Alexandrovich Kryukov 28-Nov-13 13:33pm

Exactly.
—SA

Adam Zgagacz 28-Nov-13 17:15pm

Do you have source code of your RoundUp method? By analyzing it we can tell why it is behaving this way.

Solution 4

Thanks to all for giving your valueable time

Posted 28-Nov-13 18:23pm

ErBhati

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johannesnestler · Accepted Answer · 2013-11-28T03:24:00

Solution 2

Hi ErBhati,

I'd guess your RoundUp function was created to "always round up" - seems logical for me, and seems to work as expected, no? Anyway if you want not "round up always" just use built-in
Math.Round() function...

Kind regards Johannes

Posted 28-Nov-13 3:24am

johannesnestler

Comments

ErBhati 29-Nov-13 0:23am

thanks its work for me