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c++ rmatrixlu - possibly bug in reorder out argument
http://forum.alglib.net/viewtopic.php?f=2&t=46
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Author:  marcosassis [ Thu Jul 29, 2010 7:30 pm ]
Post subject:  c++ rmatrixlu - possibly bug in reorder out argument

Hi! I'm new to alglib, but I liked very much it's style and I would like to use it in my research.
I tried to use rmatrixlu from c++ version, (last release: 2.6.0), and the decomposition worked well, but the compacted permutation matrix came wrong all the times. Something like (for a matrix 6x6): [5 5 3 5 5 5]. The way I understood this format, it could not have repeated values.
Did some one have the same problem? Is possible I'm doing something wrong?

Author:  Sergey.Bochkanov [ Fri Jul 30, 2010 5:30 am ]
Post subject:  Re: c++ rmatrixlu - possibly bug in reorder out argument

No, it's alright with function. From its documentation:
Code:
* P = P0*P1*...*PK, K=min(M,N)-1,
  Pi - permutation matrix for I and Pivots[I]


[5 5 3 5 5 5] is a sequence of elementary permutations: 0th with 5th, 1st with 5th, 2nd with 3rd, 3rd with 5th. 4th with 5th, 5th with 5th.

Author:  marcosassis [ Fri Jul 30, 2010 1:33 pm ]
Post subject:  Re: c++ rmatrixlu - possibly bug in reorder out argument

Sorry for my mystake, I'm used to other format.
Thanks a lot! It helped very much!

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