User:Devon McCormick

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Devon McCormick

Founder - New York City J Users Group

I curate the SIGAPL (Special Interest Group on APL) page under the auspices of ACM's SIGPLAN (Special Interest Group on Programming LANguages.)

Email: <<MailTo(devon AT SPAMFREE acm DOT org)>>

J Wiki Pages

Following are largely ones I've written but also includes those related to areas in which I'm interested.

o An example of using J for beginning financial data analysis.

o OLEExcel - manipulate Excel worksheets using OLE interface: Scripts/OLEExcel

o WS - save J variables to file and retrieve them: Scripts/File J Variables

o An early (unsuccessful) attempt to use the J database "JDB" on the "Netflix Challenge" data. It appears to have been unsuccessful because this dataset was too large for JDB to handle.

o Start of an attempt to detail J equivalents of basic operations in Microsoft Excel.

o An essay contrasting visual understanding with symbolic understanding.

o BigFiles - work with files larger than 2 GB: Scripts/Working with Big Files. This is now largely obsolete with the advent of 64-bit versions of J that have extended the scope of the file primitives to handle larger files.

Parallelizing J

o Some general limitations to consider when parallelizing code.

o General discussion of multi-core parallelization in J; general ideas on running threads from J.

o Simple example of writing parallel code in J.

o Detailed example of how to simply parallelize code in J. This assumes the (common) sort of problem where coordination of the various parallel processes can be handled at the point where a "master" process spins them off and that the problem domain lends itself to "coarse" parallelism. I currently run two multi-core J routines almost every day using this technique and it's worked well for years now with substantial speed-ups and little difficulty.

o Complete examples of parallel J code presented at the APL2010 conference in Berlin, Germany, in September, 2010. These are the two examples of parallel code tasks, mentioned above, as well as an implementation of mutex (mutual exclusion), all written in J (version 6.02).

o Ideas on constructing arbitrarily-large datasets for comparing the effectiveness of different parallel implementations.

o "Red or Black" game simulation -> parallelization example NYCJUG/2011-04-12/RedOrBlackGameSimulation

Presentations About J

Feel free to take anything from these for your own presentation.

o Slides of my talk on "Array Thinking" at the 2014 J Conference in Toronto.

o An introduction to J presented to Hacker School in New York in September, 2014.

o "J: the Hard Parts" - a fairly lengthy talk explaining some of the parts of J that most people find the most difficult to comprehend, given to the N-Languages Meetup group on January 21, 2014.

o Presentation of J to a "Functional Programmers" Meetup group on September 20, 2011.

o Short (five minute) introduction of J to general programming group at a language slapdown which was supposed to be held on November 17, 2010 but was canceled.

o Development of code for "Diffusion-Limited Aggregation" from an initial version coded in a more conventional format to a more "J-like" version

o "Short is Sweet" - An exposition on the importance of succinct expression (from a talk for the Kdb User Group on 12/9/2009).

Feedback -- leave me /Comments