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29. april 2003
 

Steve Swartz’s talk at the seminar Monday also brought back memories from my time as a student. In 1992, I did my diploma thesis at the Forschungszentrum Informatik (FZI) in Karlsruhe titled ‘Compiling UNITY Programs to parallel Processes in a Loosely Coupled Environment’.

The idea was to make a specification that is independent of underlying architecture and application domains and to partition this into parts suitiable for hardware and software implementation. The hardware included custom PCB design and also FPGA.  The partitioning process was interactive, the designer played an important role in the partitioning.

UNITY is a notation for specifying parallel algorithms and programs that is independent of architecture and application domains. As part of the thesis I developed a program that compiled the UNITY specifications into executable parallel processes. The compiler generated code that was running with the support of PMV (Parallel Virtual Machine) on a cluster of workstations.

On of the interesting aspects (!) of UNITY is the absence of control flow. A UNITY program consists of statements that must be executed synchronously and asynchronously. A program reaches a fixed point if all statements are executed and none changes a variable. As part of the thesis I created methods for process communication and a distributed algorithm for fixed point detection.

Steve’s talk on error handling in distributed environments made me think about the similarities of distributed enterprise applications and parallel computing.

  • The requirements for communication and synchronization are the same.
  • Steve used the notion that each record is on one node. When I worked with my theses we first assumed that each element of the specification was a single process. Later we combined several elements into one process.
  • The issues with error handling in distributed environements (aka transactions) are similar to the issues with fixed-point detection in the UNITY environment.

I think I’ll dig up my thesis and the parallel processing literature from my basement. More stuff to read!


1:49:31 PM    comment []

Microsoft material and events have always been developer focused. There has been an architectural session or two but architecture has often taken the back seat.

Now architecture has taken the front seat. Just look at the material that is now available on http://msdn.microsoft.com/architecture and http://msdn.microsoft.com/patterns. Really good stuff there.

There is also a growing interest in the community for architectural topics and guidance. I see this in our user group where we plan to focus the next user group meeting on architectural topics.

Yesterday I went to listen to Clemens Vasters and Steve Swartz. They are doing an architectural tour called the Scalable Applications Tour, Both Clemens and Steve is very good at putting things in perspective. If they come to your city, attend the seminar if you get a chance!

I especially liked their view on layers, tiers and services. The distinction between a layer and tier has always been a little fuzzy. Many have a tendency to think that layers map 1-1 with tiers, but the idea that tiers may cut through layers really makes the picture clearer. This is nicely illustrated by the presentation layer of a web application where the browser and web server are different tiers. I also liked their view on how layering is recursive; a layer is built up of layers which again are built up of layers (a la fractals). Check out their presentations!


1:44:08 PM    comment []


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