rank() needs Numerical optimization!

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rank() needs Numerical optimization!

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omorr		#1 Posted : 13 February 2012 23:52:16(UTC)
Rank: Administration Groups: Registered, Advanced Member Joined: 23/06/2009(UTC) Posts: 1,740 Was thanked: 318 time(s) in 268 post(s)		Hello, It seems that function rank() will fail with Symbolic optimization. S←mat(2,0,2,0,0,0,1,-1,2,5,-1,1,-2,-3,0,-2,-2,0,0,-6,0,0,0,6,6,0,0,0,-4,-4,6,5) N.r←rank(S) Symbolic: N.r=0 Numeric: N.r=3 None: N.r=3 Regards, Radovan Edited by user 15 February 2012 01:06:25(UTC) \| Reason: Not specified
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omorr		#2 Posted : 14 February 2012 15:36:24(UTC)
Rank: Administration Groups: Registered, Advanced Member Joined: 23/06/2009(UTC) Posts: 1,740 Was thanked: 318 time(s) in 268 post(s)		Hello, Rather strange! Please look at this picture: And the associate SMath file rank.sm Could someone read this SMath file and check it out, please. Compare it to the picture above obtained from my computer. Why the rank is different for matrix S but the same for matrix A by using different Optimization? Regards, Radovan
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Davide Carpi		#3 Posted : 14 February 2012 16:46:12(UTC)
Rank: Advanced Member Groups: Registered, Advanced Member Joined: 13/01/2012(UTC) Posts: 2,648 Location: Italy Was thanked: 1329 time(s) in 875 post(s)		Hi, I've the same problem using your file... the problem seems to be the matrix dimension (S is 6x5 matrix, A is 5x5 matrix... if you enlarge S adding a new column the difference disappears) regards w3b5urf3r
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omorr		#4 Posted : 14 February 2012 17:41:31(UTC)
Rank: Administration Groups: Registered, Advanced Member Joined: 23/06/2009(UTC) Posts: 1,740 Was thanked: 318 time(s) in 268 post(s)		w3b5urf3r_reloaded wrote: I've the same problem using your file... the problem seems to be the matrix dimension (S is 6x5 matrix, A is 5x5 matrix... if you enlarge S adding a new column the difference disappears) You are right, thank you. The same happened when we "shrink" the matrix A into the 5x4 matrix. On the other hand rank(A)= 0 only for A equals to zero matrix: rank(mat(0,0,0,0,0,0,2,3))=0 Nevertheless, it should not be this way - the rank of a matrix should not depend on the Optimization applied. There are some other questionable situations where the result is a zero matrix (all zero values in Jacobain matrix and Symbolic optimization, for example- probabelly a bug as well). I suppose this one is a bug too. Regards, Radovan Edited by user 14 February 2012 19:15:36(UTC) \| Reason: Not specified
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Andrey Ivashov		#5 Posted : 14 February 2012 19:34:09(UTC)
Rank: Administration Groups: Developers, Registered, Knovel Developers, Administrators, Advanced Member Joined: 11/07/2008(UTC) Posts: 1,616 Was thanked: 1978 time(s) in 666 post(s)		Thank you! Fixing...
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1 user thanked Andrey Ivashov for this useful post.		on 14/02/2012(UTC)
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Andrey Ivashov		#6 Posted : 15 February 2012 00:04:05(UTC)
Rank: Administration Groups: Developers, Registered, Knovel Developers, Administrators, Advanced Member Joined: 11/07/2008(UTC) Posts: 1,616 Was thanked: 1978 time(s) in 666 post(s)		Fixed.
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1 user thanked Andrey Ivashov for this useful post.		on 15/02/2012(UTC)
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