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problem with Ceiling

Rojalin

 

Hi,

I am facing problem on executing ceiling function.

when i am giving B=3.0 and c=ceiling(B) it.gives correct result 3

But when i am getting B by some calculations and execute for c it gives incorrect result.

    like B=(dx-2*via_enc)/via_pitch

          c=ceiling(B)

    it gives B=3.0 and c=4.

What can be the cause of this error?

 

Thanks

  • This is due to floating point rounding errors. It happens in every language that uses IEEE floating point representation (in fact it happens in normal base 10 arithmetic any time you have fixed precision with fractions which are not based on powers of the prime factors of the number base. There are numerous examples of this in the forum, as it has come up many times. Search for "floating point rounding" in the Community->Community Search - for example this post.

    If you do:

    sstatus(fullPrecision t)

    and look at B, it will probably be  slightly above 3.0. Alternatively do printf("B is %.15f\n" B) and see  what it shows.

    Andrew.

  • When you have set B=3.0 in the first case, the value is indeed 3.0 and getting cieled to 3.0. But, when you are calculating B using some other equation, though you are seeing the value as 3.0, it might not be exactly 3.0 because, the numbers in SKILL are double precision floating point and the default printing precision is 7. You can set the full precision using sstatus(fullPrecision t) so the sstatus fullPrecision flag can be set so that by default floating point numbers are displayed with full precision rather than being output with "%.7g" format.

  • Hi,

     Thanks for the reply.In that case if i want integer part and one digit after decimal point of a float number then is there any function for that?

     

  • atof( sprintf( nil "%.1f" number ) ) I may ask what exactly is your requirement?

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