What does Matrix. iterateAll() contractually do? Practically it seems to be row wise iteration for some implementations but it doesnt seem contractually state so in the javadoc. What is MatrixSlice if it is neither a row nor a colimn? How can i tell what exactly it is i am iterating over? On Jun 19, 2013 12:21 AM, "Ted Dunning" <ted.dunn...@gmail.com> wrote:
> On Wed, Jun 19, 2013 at 5:29 AM, Jake Mannix <jake.man...@gmail.com> > wrote: > > > > Question #2: which in-core solvers are available for Mahout matrices? I > > > know there's SSVD, probably Cholesky, is there something else? In > > > paticular, i need to be solving linear systems, I guess Cholesky should > > be > > > equipped enough to do just that? > > > > > > Question #3: why did we try to import Colt solvers rather than actually > > > depend on Colt in the first place? Why did we not accept Colt's sparse > > > matrices and created native ones instead? > > > > > > Colt seems to have a notion of parse in-core matrices too and seems > like > > a > > > well-rounded solution. However, it doesn't seem like being actively > > > supported, whereas I know Mahout experienced continued enhancements to > > the > > > in-core matrix support. > > > > > > > Colt was totally abandoned, and I talked to the original author and he > > blessed it's adoption. When we pulled it in, we found it was woefully > > undertested, > > and tried our best to hook it in with proper tests and use APIs that fit > > with > > the use cases we had. Plus, we already had the start of some linear apis > > (i.e. > > the Vector interface) and dropping the API completely seemed not terribly > > worth it at the time. > > > > There was even more to it than that. > > Colt was under-tested and there have been warts that had to be pulled out > in much of the code. > > But, worse than that, Colt's matrix and vector structure was a real bugger > to extend or change. It also had all kinds of cruft where it pretended to > support matrices of things, but in fact only supported matrices of doubles > and floats. > > So using Colt as it was (and is since it is largely abandoned) was a > non-starter. > > As far as in-memory solvers, we have: > > 1) LR decomposition (tested and kinda fast) > > 2) Cholesky decomposition (tested) > > 3) SVD (tested) >
