precision octave vs matlab

[michaelschmid1]

I don't think it's a octave bug. If it's a bug, I think I'm the culprit :-(
The complete algorithm need several hundred lines of code... so I don't think
I will put this here...
I will do some more search and if I will find a position where I don't know
why a difference occurs... I will ask again...
but then with code ...

thanks
michel


On 29-May-2006, address@hidden wrote:

| Hi all
| 
| First thanks for all the answers about my "global" problem... it works
now...
| 
| but now the next problem..
| 
| I have programmed some parts of a neural network toolbox for Octave, like
| the one of matlab. Some commands are working like "newff, train, sim" and
| so on..
| For the first training algorithm I decided to realize Levenberg-Marquardt.
| Now if I make a comparison between the results of matlab and octave, there
| are some small differences...
| I searched for calculating errors but can't find anything. As far as I
know,
| both are using double-precision ... so where does this difference come
from?
| Is it really a calculating error or only a "rounding error"?
| 
| Octave output:
| ================
| simOut =
| 
|  Columns 1 through 8:
| 
|   1.67883  2.05781  1.21596  2.82417  2.06661  2.00662  2.99825  1.65494
| 
|  Columns 9 through 16:
| 
|   1.65087  1.90819  1.90195  1.70142  2.61220  1.99405  0.99050  1.91911
| 
|  Columns 17 through 24:
| 
|   1.94686  0.93073  1.87499  1.75138  1.71708  2.21930  0.94781  2.02244
| 
|  Columns 25 through 30:
| 
|   2.01943  1.10781  2.02009  1.85863  2.71098  1.30415
| 
| matlab output:
| ==============
| 
| simOut =
| 
|   Columns 1 through 17 
| 
|     1.6767    1.9494    1.1277    2.7196    2.0406    1.9435    2.8583
 
|  1.6444    1.6437    1.8839    1.7769    1.6008    2.7412    1.9360   
1.0998
|    1.8426    1.8144
| 
|   Columns 18 through 30 
| 
|     1.0464    1.8657    1.7506    1.6612    2.1693    1.0655    1.8792
 
|  2.0094    1.0119    1.9947    1.8084    2.5923    1.2365
| 
| Of course both programmes have the same initial conditions...
| 
| I hope someone have similar experience with this kind of "trouble"
| and that this person can tell me that I didn't make a calculation error..

Given the information you have provided (just the outputs and no code)
how can anyone tell?

If you think you have found a bug in Octave, then please submit a
complete bug report to the address@hidden list.  But please read
www.octave.org/bugs.html first to learn how to submit a useful bug
report that provides enough information to allow someone to actually
fix the problem.

Thanks,

jwe