| Re: Dereferencing a large array in a structure [message #50295] |
Tue, 26 September 2006 14:26  |
btt
Messages: 345
Registered: December 2000
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Senior Member |
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Braedley wrote:
> In one of my widget programs, I have a tab widget, and the bases that
> belong to it store a fair amout of data concerning that tab in their
> uvalues. When a tab is selected, all the data in the uvalue must be
> dereferenced and loaded into common block variables. This was done so
> that other widgets within the program have quick and easy access to the
> data of the currently open tab.
>
> Enter the problem: Some of the data can be very large. One field in
> the uvalue structure can be as large as a 20 by 50000 double array (or
> larger), and it obviously can take some time to copy, especially with
> memory running low with other similarly large structures for other
> tabs. I've already set the no_copy keyword in calls to widget_control
> when setting and getting the uvalues to help reduce the load on memory
> and help out with some speed, but the million element array still needs
> referencing into the structure to be set, and dereferenced from the
> structure of the newly selected tab, which is taking up a large portion
> of the time spent. Are the any faster ways of doing this? Bonus
> points for reducing the load on memory and not making me rewrite every
> subwidget (ie not messing with the common blocks).
>
Hello,
How about storing a pointer to your data in your UVALUE instead of a
copy of the data itself.
In the widget contructor you can ...
pData = PTR_NEW(myBigData)
myStuff = {DATANAME: 'baggage',PDATA :pDATA, FLAVOR: 'vanilla'}
WIDGET_CONTROL, myBaseWidgetID, SET_UVALUE = myStuff
In the event handler you can then ...
WIDGET_CONTROL, ev.TOP, GET_UVALUE = myStuff
*(myStuff).pData = doSomething(*(myStuff).pData, FLAVOR = myStuff.flavor)
WIDGET_CONTROL, ev.TOP, SET_UVALUE = myStuff
Don't forget to free the pointer memory when the widget hierarchy dies
(or when ever you want it to.)
The common block stuff is throwing me off a bit. This isn't an IDL EPA
quiz is it? (http://www.dfanning.com/misc_tips/iepa.html)
Cheers,
Name Withheld Just In Case It Is A Quiz
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