Armando,
Memory associated with GISDK macro variables is freed when the variables are
set to null or when the macro exits. The only exceptions to this is when the
value is stored in a shared, static or a global variable, then the value
persists throughout the session and will not be freed until the shared variable
is set to null. If that is not done, it persists until the program shuts down.
How you resize your arrays can affect memory performance. As you note, myArray
= myArray + {value} is slower than using dim[]. In the end, the same
theoretical amount of memory would be used. However, there might be some
memory fragmentation taking place as a result.
I see you are familiar with vectors. I would encourage you to use them as they
are more efficient than arrays. Since all the vector elements are of the same
type, less memory is used for every element (the type information only needs to
be stored once for the vector, instead of once for every element). And the
vectors offer many very efficient operations. You can add them (v3 = v1 + v2),
use them in conditional expressions (w = if v>0 then 1 else 0) and you can pass
them to functions (w = 1+sin(v)). In many cases a single statement can replace
a potentially slow GISDK loop on arrays.
-Kjartan
From: [email protected] [mailto:[email protected]] On Behalf Of
Armando Scalise
Sent: Monday, February 21, 2011 12:19 PM
To: [email protected]
Subject: [Maptitude] Garbage colleciton and memory management in GISDK
I wonder wehter someone in Caliper could shred some light into memory mangement
and garbage colleciton in GISDK
I am bumping into memory issues in a macro that handles very large (millions
of records) multidimensional arrays.
My initial macro had a number of those arrays defined, so I splitted the code
and use the vectors one at a time in separate macros. The memory issues still
persist
Before rewriting my code to a disk-based data management as opposed to using
memory arrays. I would very much appreciate if you could provide some input on
the folloiwng questions:
- Does GISDK frees up all the memory macro uses (for exmaple, arrays that
are only used within the macro and not passed back as ouput) once the macro is
terminated?
- If so, when does this happen? immediately after the macro is finished?
or randomly?
- If I have a large array in a macro, and I set it to null before leaving
the macro, does that liberates memory immediately?
- Does an expression like myArray = myArray + {newvalue} when used
recursively imposes a toll on memory usage? (I know that Dim myArray[n] is
more efficient, but often times I ignore the dimension the array will end up
having)
- Are there any specific guidliness or reccomendations for using large
arrays in the DK?
Thanks
--
Armando Scalise
