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Re: SPAWN [message #8749 is a reply to message #8682]

Fri, 11 April 1997 00:00

davidf
Messages: 2866
Registered: September 1996

Senior Member

Nobuyuki Tasaka <tasaka@mr.med.ge.com> writes:

> If someone who have tried to compare SPAWN in the following
> usage, please let me know the difference in terms of data
> parsing speed, interface flexibility and routine's independency.
>
> I would like to use SPAWN for calling database retriving routine
> written in C.
>
> 1) SPAWN, "cmd", result

This is the least flexible way of using SPAWN, I think. You can
only ask one "question" at a time and then you have the problem
of parsing the "result" to get the answer you want.

> 2) SPAWN, "cmd", /UNIT

This method is much more flexible in terms of interaction with
your database, but it is restricted to UNIX platforms. If you want
to pass large amounts of data back and forth and can be slow and,
of course, you have to make two copies of every piece of data,
which is not resource friendly. Call_External would probably be
a better choice if you decided to go down this path. It would give
you the ability to share memory resources with your database
access program.

> 3) SPAWN, "cmd"
> (C routine writes data to memory map file and then IDL read it
> as a Logical Unit File)

This has several huge advantages. First, it is extremely simple
to implement. You don't need any special knowledge about
operating sytems, linking protocols, etc. And second, it works
on every platform IDL supports. You don't have to write special
code when you decide to port from your Suns to the PC or Mac.
On the downside, if you are transferring large amounts of data
it can be slower than you would like.

If you are really serious about doing this, I would look into
Call_External as a possibility. Or, perhaps even better, wait
for IDL 5 and the new database connection tools. This problem
may have already been solved for you! :-)

Cheers!

David

-----------------------------------------------------------
David Fanning, Ph.D.
Fanning Software Consulting
2642 Bradbury Court, Fort Collins, CO 80521
Phone: 970-221-0438 Fax: 970-221-4762
E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com
-----------------------------------------------------------

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[Message index]

		SPAWN By: Nobuyuki Tasaka on Tue, 08 April 1997 00:00
		Re: SPAWN By: alpha on Wed, 16 April 1997 00:00
		Re: SPAWN By: davidf on Fri, 11 April 1997 00:00
		Re: spawn By: marc schellens[1] on Thu, 17 February 2000 00:00
		Re: spawn By: marc schellens[1] on Thu, 17 February 2000 00:00
		Re: spawn By: Craig Markwardt on Wed, 16 February 2000 00:00
		Re: spawn By: Benno Puetz on Mon, 06 March 2000 00:00
		Re: Spawn By: Michael Galloy on Thu, 31 July 2008 10:21
		Re: Spawn By: mankoff on Thu, 31 July 2008 05:38
		Re: Spawn By: Joost Aan de Brugh on Thu, 31 July 2008 05:37
		Re: Spawn By: Bob[3] on Thu, 31 July 2008 05:33
		Re: Spawn By: Allan Whiteford on Thu, 31 July 2008 04:56

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