MatrixRank[m, Modulus -> 5] is broken

*To*: mathgroup at smc.vnet.net*Subject*: [mg97055] MatrixRank[m, Modulus -> 5] is broken*From*: ilan <ilanorv at cs.bgu.ac.il>*Date*: Wed, 4 Mar 2009 07:11:23 -0500 (EST)

I have a strange problem. I ask for MatrixRank of matrix over the reals without Modulus and I get some number, assume 5; next I add a raw into this matrix and ask for the rank and I get 5; next I do both calculations using Modulus -> 7 and get 4 and 5. There is a problem!!! if a the additional raw was linear depended over the reals, it m-u-s-t be linear depended over Modulus because a linear combination for this extra row using other rows is valid when we apply Modulus -> 7. Therefor I suppose to get 4 and 4. what is the conclusion?

**Follow-Ups**:**Re: MatrixRank[m, Modulus -> 5] is broken***From:*Daniel Lichtblau <danl@wolfram.com>