Thank you, Ted.
On Wed, Jun 19, 2013 at 12:20 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) >
