| Re: Multithreading in IDL [message #44875] |
Tue, 26 July 2005 07:25  |
Marc Reinig
Messages: 30
Registered: June 2004
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Member |
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"Tiago St�rmer Daitx" <tdaitx@gmail.com> wrote in message
news:1122379580.769915.254950@g43g2000cwa.googlegroups.com.. .
> IDL itself can be set to run multithread even on a single processor
> system. Simply run CPU, TPOOL_NTHREADS = NumThreads and you're set.
>
> So far my experience says that on Linux there'll be a process for each
> thread and on Windows all I could get was a single process, no matter
> what - maybe I'm doing something wrong, but my guess is that is the way
> multithreading works on Windows (note that I neither own a SMP system
> nor have access to one).
On Windows, processes are ~the equivalent of a program that you run. The
process can, in turn, have multiple threads. They all share the same
address space and resources. They can also run simultaneously on multiple
processors.
IDL supports multiple threads internally on Windows for some operations.
FFT is one. We have an 8 processor machine. When it hits the FFT's all 8
come alive. When it goes back to regular code, only one is active. There
are probably some Matrix operations that are also mutli threaded.
You can do your own multi threading using a DLM to spawn separate threads in
Windows, but I haven't done it to use IDL functions.
Marc Reinig
System Solutions
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| Re: Multithreading in IDL [message #44878 is a reply to message #44875] |
Tue, 26 July 2005 05:06  |
tdaitx
Messages: 5
Registered: July 2005
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Junior Member |
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IDL itself can be set to run multithread even on a single processor
system. Simply run CPU, TPOOL_NTHREADS = NumThreads and you're set.
So far my experience says that on Linux there'll be a process for each
thread and on Windows all I could get was a single process, no matter
what - maybe I'm doing something wrong, but my guess is that is the way
multithreading works on Windows (note that I neither own a SMP system
nor have access to one).
Now, if you're asking about threading support for your code, I must say
that IDL doesn't provide any means to do it (someone please correct me
if I'm wrong here). If you want your code to spawn some threads and get
a handle of it you'll have to wait till RSI decides to support thread
programming.
A creepy way I can think of to let a piece of code running in the
background while a main program runs (or not if you want so) is
creating a base widget with Map 0 and register it with Xmanager using
the No_Block keyword, since Xmanager can run tasks in the background.
It's an ugly workaround and I didn't dare to try it (yet), but it's
there if someone wants to give it a shot.
And, finally, you can always choose to use call_external or link_image,
but it's almost the same as using the Xmanager trick, what you get is
multiprocessing, not multithreading. Take a look at the Multithreading
topic
( http://groups-beta.google.com/group/comp.lang.idl-pvwave/bro wse_thread/thread/f49fb0d9810cd530/b51116bb6b96cf71)
Regards,
Tiago S Daitx
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| Re: Multithreading in IDL [message #44953 is a reply to message #44878] |
Fri, 29 July 2005 06:20 |
Ricardo Bugalho
Messages: 22
Registered: March 2005
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Junior Member |
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On Tue, 26 Jul 2005 05:06:20 -0700, Tiago St�rmer Daitx wrote:
> So far my experience says that on Linux there'll be a process for each
> thread and on Windows all I could get was a single process, no matter what
> - maybe I'm doing something wrong, but my guess is that is the way
> multithreading works on Windows (note that I neither own a SMP system nor
> have access to one).
Actually, that's a flaw of old threads implementation in Linux. You should
not see one process per thread. Threads should be part of the process. The
modern threads implementation doesn't have that bizarre effect.
>
> A creepy way I can think of to let a piece of code running in the
> background while a main program runs (or not if you want so) is creating a
> base widget with Map 0 and register it with Xmanager using the No_Block
> keyword, since Xmanager can run tasks in the background. It's an ugly
> workaround and I didn't dare to try it (yet), but it's there if someone
> wants to give it a shot.
Doesn't work, XMANAGER is a loop running everything in the same thread.
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