[PRL] Kean Walmsley on using F# Asynchronous Workflows to simplify concurrent prog...

[Mitch]

Somebody want to give a talk on this Asynchronous Workflow stuff?

--Mitch

Sent to you by Mitch via Google Reader: Kean Walmsley on using F#
Asynchronous Workflows to simplify concurrent programming in AutoCAD
via Don Syme's WebLog on F# and Other Research Projects by dsyme on
1/27/08
On Friday Kean Walmsley posted an excellent article on Using F#
Asynchronous Workflows to simplify concurrent programming in
AutoCAD.I've quoted some it below.

There are two things I especially like about this post. First, Kean's
code is very clean and some of the best F# app-extension scripting I've
seen.

Second, Kean took the time to highlight the minor differences between
the synchronous and parallel versions of his algorithm. Of the 235
lines, only 13 lines of code and 7 lines of comments changed, and even
for those there is a very close correspondence between the versions.
Allowing programmers to achieve this correspondence was one of the key
design goals of asynchronous workflows.

Here are some snippets from Kean:
As promised, in today's post we take that code and enable it to query
the same data in parallel by using Asynchronous Workflows in F#.
Asynchronous Workflows are an easy-to-use yet powerful mechanism for
enabling concurrent programming in F#.
Firstly, a little background as to why this type of technique is
important. ... Barring some disruptive technological development, the
future gains in computing performance are to be found in the use of
parallel processing, whether via multiple cores, processors or
distributed clouds of computing resources. ... Additionally, with an
increasing focus on distributed computing and information resources,
managing tasks asynchronously becomes more important...
The big problem is that concurrent programming is - for the most-part -
extremely difficult to do, and even harder to retro-fit into existing
applications...
Today's post looks at a relatively simple scenario, in the sense that
we want to perform a set of discrete tasks in parallel, harnessing
those fancy multi-core systems for those of you lucky enough to have
them (I'm hoping to get one when I next replace my notebook, sometime
in March)...
We are also going to be very careful only to run parallel tasks
unrelated to AutoCAD. Any access made into AutoCAD's database, for
instance, needs to be performed in series: AutoCAD is not thread-safe
when it comes to the vast majority of its programmatically-accessible
functionality. So we're going to run a set of asynchronous, parallel
tasks to query our various RSS feeds, and combine the results before
creating the corresponding geometry in AutoCAD. This all sounds very
complex, but the good (actually great) news is that Asynchronous
Workflows [do] all the heavy lifting....

In an earlier post I linked to Kean's entries where he had written his
first AutoCAD application using F# and has just followed up with A
mathematical F# application integrating with AutoCAD via .NET which
embeds one of the F# DirectX demos directly into AutoCAD.



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