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## Is this a numerical problem?

**From**: |
Lukas Reichlin |

**Subject**: |
Is this a numerical problem? |

**Date**: |
Thu, 19 Aug 2010 10:39:45 +0200 |

Dear Octave community
I'm using Octave 3.2.4 from MacPorts on MacOSX 10.6.4 running on an Intel Core
2 Duo. I noticed a behaviour which seems strange to me. Does someone have a
good explanation for the results below?
octave:60> a = (10 * rem (-12/5, 1))
a = -4.00000000000000 # a < -4
octave:61> fix (a)
ans = -3 # I'm expecting -4
octave:62> a + 4
ans = 8.88178419700125e-16 # I'm expecting something negative
# While this is working as expected
octave:63> b = -4.001
b = -4.00100000000000
octave:64> fix (b)
ans = -4
octave:65> b + 4
ans = -0.00100000000000033
The same with R2009a:
>*> a = (10 * rem (-12/5, 1))*
a =
-4.0000
>*> fix (a)*
ans =
-3
>*> a+4*
ans =
8.8818e-16
>*> b = -4.001*
b =
-4.0010
>*> fix (b)*
ans =
-4
>*> b + 4*
ans =
-0.0010
>*> *
Best Regards,
Lukas

**Is this a numerical problem?**,
*Lukas Reichlin* **<=**
**Re: Is this a numerical problem?**, *Jaroslav Hajek*, `2010/08/19`
**Re: Is this a numerical problem?**, *Lukas Reichlin*, `2010/08/19`
*Message not available*
**Re: Is this a numerical problem?**, *Jaroslav Hajek*, `2010/08/19`
**Re: Is this a numerical problem?**, *Lukas Reichlin*, `2010/08/19`
**Re: Is this a numerical problem?**, *Sergei Steshenko*, `2010/08/19`
**Re: Is this a numerical problem?**, *Jaroslav Hajek*, `2010/08/19`
**Re: Is this a numerical problem?**, *Miguel Bazdresch*, `2010/08/19`
**Re: Is this a numerical problem?**, *Lukas Reichlin*, `2010/08/19`
**Re: Is this a numerical problem?**, *Jaroslav Hajek*, `2010/08/19`