Thanks Chameera and Sebestian for sharing your expertise :) Just wanted to know the reason behind the absence of an equality check for Matrices.
Regards, On Sun, Dec 29, 2013 at 10:25 PM, Sebastian Schelter < ssc.o...@googlemail.com> wrote: > Ah, I see, you just pointed to the issue, sorry misread your mail. > > The problem is that checking matrices and vectors for equality is a very > costly operation (you have to compare at least all non-zero entries). > For that reason, we did not implement equals correctly (which is in > general a very bad thing). > > We advise users not use vectors and matrices in places where equality > checks on them are necessary (e.g. in a HashSet or as key in a HashMap) > > A way to manually check the equivalence of two dense matrices is to > compare all entries. > > --sebastian > > > On 29.12.2013 17:49, Chameera Wijebandara wrote: > > Sebastian, > > Yes It's not enought to check the reference. i mean > DenseMatrix*.*equals() > > methord does that and it cannot use for check equity is that wrong? > > > > > > > > On Sun, Dec 29, 2013 at 8:40 AM, Sebastian Schelter <s...@apache.org> > wrote: > > > >> Chameera, > >> > >> This is wrong. It's not enought to check the reference, two different > >> instances can be semantically equivalent, > >> > >> A dense matrix represents its entries in a two dimensional double array. > >> You have to check for the equality of these arrays. > >> > >> --sebastian > >> > >> On 29.12.2013 17:14, Chameera Wijebandara wrote: > >>> Hi Tharindu > >>> > >>> In the DenseMatrix class does not implement equals method so it use > >>> Object.equals witch check the reference. > >>> You have implement equals method by overriding Object.equals method. > >>> > >>> Thanks > >>> Chameera > >>> > >> > >> > > > > > > -- M.P. Tharindu Rusira Kumara Department of Computer Science and Engineering, University of Moratuwa, Sri Lanka. +94757033733 www.tharindu-rusira.blogspot.com
