Is performance in LUD normally achieved by fast element access? Or is it done by using higher order operators on a view of a row (or column)?
I know the the Colt package made the argument that the latter it far preferable. I also know that Jama didn't do this, but was very hard to extend as a result. The colt approach was to require the matrices provide row, column and submatrix view operations and that vectors and matrices support functionally oriented destructive updates. This can be hard for users to understand so you generally have to provide more algebraic interfaces as well, but it can work wonders for performance. On Mon, Dec 1, 2008 at 2:52 PM, Luc Maisonobe <[EMAIL PROTECTED]> wrote: > For now, one thing that bother me is the removal of the dedicated code > that explicitely avoided getEntry(). This was added a few months ago for > performance reason, since the previous generic code was painfully slow. > The trick with the ClassCastException allows really fast check since the > virtual machine can completely optimize it out in some cases, it is an > enhancement of what was discussed here: > http://markmail.org/message/36fgg7vx6gzd3ziu. Our discussion at that > time was that the more common case (RealMatrixImpl) should be as > efficient as possible (and Ted wants now it to be even faster by > changing the underlying storage which is a good thing). This trick is > not beautiful perfectly generic code, it is a pragmatic way to be fast > in a common case and removing it will most probably induce poorer > performances. > -- Ted Dunning, CTO DeepDyve 4600 Bohannon Drive, Suite 220 Menlo Park, CA 94025 www.deepdyve.com 650-324-0110, ext. 738 858-414-0013 (m)
