Archive for March, 2008They loseMarch 27th, 2008 by PeterWhile preparing my parallel programming lecture for the server architecture course, I read some articles (like here and here) about MapReduce and the hot discussions about it in the database community. BTW, if you ask yourself where the relation is, you already got it right. During this crawl, I found a great presentation from Joseph M. Hellerstein on the never-ending sadness of database people. Just read it, especially if you belong to the ‘opposite’ side such as me …. Parallel Monte CarloMarch 27th, 2008 by PeterI was recently asked for some initial material on running larger Monte Carlo simulations on clusters and Grids. In general, the solution is obvious, since Monte Carlo is one of the embarrassingly parallel problems (some introduction slides). You can find application reports for areas such as financial derivatives pricing. The easiest explanation I could find is this one by Paul Gray. It shows an example of how a parallel Monte Carlo simulation can look like. Parallel MC has the problem of generating trustable random numbers, as described here and here. All your mail rejected ?March 26th, 2008 by PeterAccording to the usual news sites (e.g. Slashdot), the old ORDB spam blacklist (closed in 2006) now returns false positives for all queries. This is rather nasty, since mail systems still using it now mark all checked mails as spam. Depending on the configuration, this either rejects or at least sorts out all incoming mails. This does not only relate to mail servers, but also to all kind of client-side spam filter plugins and tools. Old versions of Spamassassin are a good candidate. The Heise article explains that this is intended as some kind of wakeup call, in order to reduce the still high amount of useless queries. Deleting the domain is argued to be a non-valid solution, since the load then goes to the .org name servers. This is really the strange part of the argumentation, since it completely ignores the DNS negative response caching mechanisms (see RFC 1034, section 4.3.4, and RFC 2308, or here). They are part of Bind since 1996. |