sutton036

O'Reilly just published a new book, the Mathematica Cookbook , about Wolfram Research's flagship product. This book contains many interesting examples from various different disciplines. Most of these are derived from freely available examples written by other people (primarily from Wolfram Research's original Mathematica Book and also the excellent Wolfram Demonstrations Project ) but the author has simplified some of the programs to make them more accessible. However, the density of the information in this book is incredibly low. Most pages are filled with superfluous Mathematica output that is often not even described in the text: Dozens of triples on page 15. Page 58 lists hundreds of numbers but the text does not even describe their significance. Page 205 lists all of the words with a subset of the letters "thanksgiv". Page 226 is raw XML data. Pages 264-265 are solid code that renders a snowman with circles and some dots for snow (all in black and white). Pa...

This recent paper describes the state-of-the-art in Data Parallel Haskell (DPH). Some of the code referred to in the paper is available here . This post is in response to a question from one of the coauthors, Roman Leshchinskiy, asking what is wrong with the paper. The problem with this paper is, in a word, cache . Specifically, the widespread adoption of CPU caches two decades ago forced a change in the way programmers traverse data structures when performance is of interest. The old style was to iterate directly using a for loop. The new style is either a cache aware set of loops that exploit knowledge of the sizes of caches in the machine, or a cache oblivious style that uses divide and conquer to subdivide the problem until it fits in-cache regardless of the cache's size. This paper uses neither of the modern approaches, opting instead to use direct loops that have not been seen in real numerical code for several decades. The paper incorrectly asserts that these are "wi...

We just finished a week of hell after trying and failing to upgrade from Debian Lenny to Debian Squeeze. None of the Debian Linux kernels working correctly on our stock Dell PowerEdge T605 hardware was the first major headache and KDE 4 was the second. In our 10 years of using Linux its user unfriendliness seems to be as poor as ever. With the latest KDE 4, it seems that KDE itself has also gone from bad to worse. We migrated from Gnome to KDE many years ago because we found Gnome to be buggy and user unfriendly only to discover that KDE was only superficially stable. KDE 4 takes this to a new level and our log files are filled with records of segfaults. KMail was once riddled with serious bugs but these were ironed out in KDE 3 and it became a usably-stable e-mail client a few years ago and served us well. Not so with KMail from KDE 4, which regularly segfaults, losing and/or corrupting data and has consistently failed even to move significant numbers of e-mails around within its own ...