Hello all, This is excellent discussion, but I am less concerned at this stage with whether the result is pre-computed vs computed on the fly, than I am with knowing that someone in the community wants a particular result to be provided, and there is a reasonable case (the 6 criteria) to include it in LSST.
Once we have that defined, we can do the implementation trade off that lets us decide whether to pre-compute or not, and from that we can size accordingly. I'm also NOT trying to come up with an exhaustive list at this point; one use case/data product/query for each of the listed items would be a great start. Jeff > From: "Kem Cook" <[EMAIL PROTECTED]> > Reply-To: LSST Data Management <[email protected]> > Date: Mon, 27 Mar 2006 13:31:05 -0800 (PST) > To: "LSST Data Management" <[email protected]> > Subject: Re: [LSST-data] WRT Kem's summary > > I think Dave's wide common proper motion pair is an example of a community > use case which won't be precomputed by LSST. A bit more tractable > astrometric use case, might be to identify streams or moving groups in > some (limited) region of the sky. > > Sorry, it was 6 criteria for determining whether LSST delivers the data > product. Using those criteria a parametrization of variability is almost > certainly provided. > > By the way, in my ignorance, I don't understand why the wide pair problem > is so hard. Sort on one element of PM, find pairs, check the other > element. Is it the 200,000,000 element sort that kills one? I thought > there were some pretty fancy sort algorithms these days. > > Kem > >> I hit the "d" key too quickly. Was a gross parameterization of >> photometric >> variability one of Ken's 6 enabling computations? >> >> With respect to how big we let the DM load get, are there ground rules >> as to the sorts of queries that LSST will accept? Wearing my Pan-STARRS >> hat, I tried to break SAIC's implementation of Oracle's version of USNO-B >> by giving it the wide physical pairs problem in SQL. The task is to see >> if there are pairs of stars with similar proper motions but very widely >> spaced on the sky (as differing from the normal common proper motion >> problem where the stars are relatively close together on the sky). >> Needless to say, Oracle never did finish looking for any star with >> another star having the same motion but more than 150 degrees away. >> Its default search was about as inefficient as one can imagine, and >> N**2 searches where N is big can take a very long time. >> >> At what level of complexity does the server reject a query, and once >> rejected, what is the path for the user to take into the LSST archive? >> >> -Dave >> _______________________________________________ >> LSST-data mailing list >> [email protected] >> http://www.lsstmail.org/mailman/listinfo/lsst-data >> > > _______________________________________________ > LSST-data mailing list > [email protected] > http://www.lsstmail.org/mailman/listinfo/lsst-data > _______________________________________________ LSST-data mailing list [email protected] http://www.lsstmail.org/mailman/listinfo/lsst-data
