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Re: 6.3 reactions? [message #48671 is a reply to message #48556]

Tue, 09 May 2006 11:54

JD Smith
Messages: 850
Registered: December 1999

Senior Member

On Tue, 09 May 2006 00:23:57 -0400, Richard G. French wrote:

> I hope that someone who really understands all of this IDL Bridge stuff
> and who doesn't use objects for every programming task will provide a
> simple description for civilians of just what this capability can do for
> the everyday user, and what it can't do. I'm having trouble figuring out
> whether this is a cool feature that I'd be crazy not to employ, an easy
> way to try to do parallel processing, or something that would require me
> to reprogram everything I do to obtain the leverage from multiple
> processors. So, all of you Ernest Hemingways out there, how about some
> simple, declarative sentences with an example or two of how this feature
> works and why it is a Good Thing. Many of us will be grateful!

Having not used it, as far as I can tell it's a convenient wrapper
around pre-existing functionality. You could already, with IDL
versions prior to 6.3, spawn another IDL process, setup a shared
memory channel of communication between them, copy variables back and
forth, and use an inter-process communication method, with special
communication code running on each side, to notify the parent process
when the child process is done with processing. Then you could read
back some results, and make use of them. It was just a big pain.

The new Bridge just makes that all easy for you... no need to setup
shared memory and/or some other access (like a semaphore) to
communicate back and forth, no need to poll to find out if a process
is done with some calculation. Just use Get/Set to send variables (by
copying) back and forth through shared memory, use callbacks to get
notified when processing is complete, etc. This would be useful if you
have a GUI front-end, which you'd like to keep responsive while
another IDL process chugs away on some big calculation. Basically, if
you like background processing of widget events, you'll love the
bridge, because you can have *anything* be background processed.

I don't know what the overhead for starting this sub-process and setting
up shared memory is, so it may only pay for really intensive calculations.
It would also be a potential speedup if you have a problem which
doesn't make use of large enough arrays (a few hundred thousand
elements) to benefit from IDL's native threading on multi-processor
machines. Again, the key factor determining how useful this will be
is the overhead involved in setting up the child process. Does it
really go through the entire rigmarole of contacting the license
server, expanding and searching the IDL_PATH, etc., establishing the
graphics devices, etc.? If so, it will be too heavy-weight for
speeding up smaller scale operations, but of course will be useful for
those 1 min or longer operations which otherwise would have blocked.

One other factor to consider: I presume that if you had a large pile
of data in process A, and you wanted to spawn sub-process B to work on
that data in the background, you'd end up with *two* copies of that
data in memory, one each in the space of processes A and B, unless you
specifically remove that data on one side, then the other (e.g. with
TEMPORARY). You thought preventing memory leaks was hard with one IDL
process...

JD

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[Message index]

		6.3 reactions? By: Richard French on Mon, 01 May 2006 20:31
		Re: 6.3 reactions? By: codepod on Fri, 05 May 2006 07:25
		Re: 6.3 reactions? By: JD Smith on Fri, 05 May 2006 09:24
		Re: 6.3 reactions? By: Haje Korth on Thu, 04 May 2006 09:28
		Re: 6.3 reactions? By: R.Bauer on Thu, 04 May 2006 01:26
		Re: 6.3 reactions? By: codepod on Thu, 11 May 2006 13:15
		Re: 6.3 reactions? By: wem on Thu, 11 May 2006 10:26
		Re: 6.3 reactions? By: Haje Korth on Thu, 11 May 2006 10:06
		Re: 6.3 reactions? By: Foldy Lajos on Wed, 10 May 2006 10:24
		Re: 6.3 reactions? By: Haje Korth on Wed, 10 May 2006 09:33
		Re: 6.3 reactions? By: Craig Markwardt on Wed, 10 May 2006 08:23
		Re: 6.3 reactions? By: Mark Hadfield on Tue, 09 May 2006 16:21
		Re: 6.3 reactions? By: JD Smith on Tue, 09 May 2006 11:54
		Re: 6.3 reactions? By: JD Smith on Tue, 09 May 2006 11:59
		Re: 6.3 reactions? By: David Fanning on Tue, 09 May 2006 10:50
		Re: 6.3 reactions? By: codepod on Tue, 09 May 2006 10:30
		Re: 6.3 reactions? By: Richard French on Mon, 08 May 2006 21:23
		Re: 6.3 reactions? By: JD Smith on Mon, 08 May 2006 13:25
		Re: 6.3 reactions? By: codepod on Mon, 08 May 2006 07:29
		Re: 6.3 reactions? By: David Fanning on Fri, 05 May 2006 09:55

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