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PROBLEM:
I noticed that when I work with strings, particular LARGE strings, the time that is involved to build them can be quite long. Some of my routines take up to 1 minute 53 seconds to build up the result. Since this is done in a web environment, there are two problems:
1) The response is very late causing people to close the browser, navigate away etc
2) Sometimes we run in a time-out (set to 2 minutes) and people get an error
ANSWER:
When you work with large strings you are working with memory allocations/reallocations and copying. Speed all depends on paging/caching, how efficient the memory manager is at allocating small/large chunks of memory as well as disposing the memory (i.e. freeing up memory).
If your program does something like:
Move '' To sLongString
For iLoop From 1 to 1000000
Move (sLongString + 'x') to sLongString
Loop
it is much slower than when you do:
Move '' To sLongString
For iLoop From 1 to 1000
Move '' to sTemp
For iLoop2 From 1 to 1000
Move (sTemp + 'x') to sTemp
Loop
Move (sLongString + sTemp) To sLongString
Loop
In the above example we found a difference in the order of 50 times -- where the first routine took 53 seconds, the second one took just over 1 second to complete.
NOTE:
This is NOT specific to (Visual) DataFlex. It happens in other programming environments as well, such as Javascript, XSLT scripts, 'C' etc.
Contributed By:
Vincent Oorsprong
Company: Data Access Worldwide
email: vincent.oorsprong@dataaccess.eu
Web Site: http://www.dataaccess.eu
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