| Re: Running processes in parallel [message #49338 is a reply to message #49243] |
Wed, 12 July 2006 16:12  |
Roberto Monaco
Messages: 11
Registered: August 2002
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Junior Member |
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I had a similar problem (to stop a time consuming process by pressing a
button) and wanted to experiment with IDL_IDLBridge, so created a program
that calls David's progressbar and sets a shared memory flag when the
"cancel" button is pressed. It is called through a IDL_IDLbridge (as a
separate process) before entering the loop, for example:
oBridge = OBJ_NEW("IDL_IDLBridge") ; create the child process
; create shared memory (2 elements array: a flag and the value to pass
; to progressbar to show progress)
SHMMAP, 'progressbar_shm', 2, /INTEGER
shm_var = shmvar('progressbar_shm')
shm_var[0] = 0
; lauch a progress bar
oBridge->EXECUTE, "progressbar_bridge", /NOWAIT
; the loop ends if shm_var[0] is set (the cancel button was pressed)
i = 0
WHILE i LT 10 AND NOT shm_var[0] DO BEGIN
shm_var[1] = i*10.0
i = i + 1
; here comes the time consuming thing inside the loop (simulated by
wait)
WAIT, 10
ENDWHILE
;; destroy the object and unmap shared memory
OBJ_DESTROY, oBridge
SHMUNMAP, 'progressbar_shm'
PRO progressbar_bridge, TEXT=text
; create a 2-element fix array shared memory block
; progressbar_shm[0] = flag (=1 if <CANCEL> was pressed, =0 otherwise)
; progressbar_shm[1] = progress (the fix number to update the
progressbar)
SHMMAP, 'progressbar_shm', 2, /INTEGER
shm_var = SHMVAR('progressbar_shm') ;
shm_var[1] = 0 ; starts with progress = 0%
pbar = OBJ_NEW('progressbar', TEXT=text)
pbar->Start
WHILE NOT shm_var[0] DO BEGIN
pbar->Update, shm_var[1]
IF pbar->CheckCancel() THEN $
shm_var[0] = 1 ; set flag=1
WAIT, 0.1 ; refresh every 10th of second
ENDWHILE
pbar->Destroy
SHMUNMAP, 'progressbar_shm'
END
I had done some adaptation to progressbar time ago, so I am not sure this
works with the original... anyhow I hope it helps or gives some ideas.
Roberto
"Michael Galloy" <mgalloy@gmail.com> wrote in message
news:7Ladnc67C4kgxyjZnZ2dnUVZ_tWdnZ2d@comcast.com...
> WorkerAnt wrote:
>> Currently, there is a for loop in my program that takes anywhere from a
>> couple of seconds to a couple of minutes. (The procedure runs a step by
>> step animation using the wait function). It's called from an event
>> handler whenever a button in the widget is pushed. I want to be able to
>> stop anytime in the middle of the animation when another button is
>> pressed. (As opposed to the ctrl break method).
>> However, the event handler is unable to process the stop button getting
>> pushed until the for loop procedure is complete, thus defeating the
>> purpose. Is there any way to run two procedures in parallel? Or a time
>> independent way to have one take priority over another?
>> Barring these two possibilities working, is there any other way of
>> having the animation stop?
>>
>
> Yes there is a way to do this: use timer events. You'll need someplace to
> store data (like a "state" structure, member variables of an object, etc.)
> The basic steps would be, in your current event handler:
>
> 1. If the event was a "stop" button, then set a "stop" flag and exit.
> 2. If the "stop" flag is set, exit.
> 2. Do one step and record that you did the step (so you know which step
> to do the next time).
> 3. Set a timer (using "WIDGET_CONTROL, id, TIMER=t" instead of using
> "WAIT, t").
>
> You could probably do this using the IDL_IDLBridge now, in a way that is
> more in line with your original strategy. I don't have a lot of experience
> using it, but it seems like there is a fair amount of overhead in using
> it.
>
> Mike
> --
> www.michaelgalloy.com
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