Initialization and memory allocation

Describes how memory is allocated to data initialization.

In OPL, the initialization mode you choose affects memory allocation. Namely, external initialization from a .dat file, while enabling a more modular design, may have a significant impact on memory usage.

Internal initialization

Internal data (directly from the model file) is initialized when first used. This is also called lazy initialization. Unused internal data elements are not allocated any memory. In other words, internal data is pulled from OPL as needed.

Example of lazy initialization

int a=2;
int b=2;

int a2=2*a;
int b2=2*b;

execute
{
 a2;
 
 a++;
 b++;
 writeln(a2);
 writeln(b2);
}

assert a2==4;
assert b2==6;

External initialization

In contrast, data from a data file is initialized while the .dat file is parsed and is allocated memory whether it is used by the model or not. In other words, external data is pushed to OPL.