On 11/08/2013 09:20 PM, Phil Steitz wrote: > On 11/8/13 11:59 AM, Ted Dunning wrote: >> On Fri, Nov 8, 2013 at 11:47 AM, Luc Maisonobe <l...@spaceroots.org> wrote: >> >>>> is there still consensus that we are going to remove the sparse >>>> implementations with 4.0? >>> Well, I really think it is a pity, we should support this. But lets face >>> it: up to now we have been unable to do it properly. Sébastien who tried >>> to do something in this direction has left the project and nobody >>> replaced him. >>> >> I have done a fair bit of noodling and was unable to come up with a >> solution that is performant. >> >> The issue is that you essentially have to maintain a additional bitmask of >> exceptional values in addition to the implicit bitmask of non-zero >> elements. I don't see any way of determining that exceptional value >> bitmask short of a full scan. Moreover, the cost of propagating the >> exceptional value bitmask significantly changes the cost of various >> operations because exceptions require an OR while multiplication allows use >> of an AND. Furthermore, even after the operation itself and the operation >> on the exception bitmask are done, there needs to be another scan of the >> results to find new exceptional values. >> >> >> So the upshot is that dealing with this will cost at least a significant >> integer degradation in performance at no benefit relative to the normal >> user's expectations with regard to sparse vector operations. I say no >> benefit because no other package handles this sort of issue so users are >> very used to imprecise handling of exceptional values. >> > So why not just "doc and punt" - document the deficiencies that we > know about and the fact that we are not going to try to "fix" them > (which, IIUC is what other packages do)?
+1, I think removing the sparse matrix implementations w/o an alternative will leave a lot of users quite puzzled. Thomas --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org For additional commands, e-mail: dev-h...@commons.apache.org
