ILOG OPL Development Studio Language Reference Manual

Initialization and memory allocationIn OPL, the initialization mode you choose affects memory allocation. Namely, externalinitialization from a .dat file, while enabling a more modular design, may have a significantimpact on memory usage.Internal initializationInternal 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 otherwords, internal data is “pulled” from OPL as needed.Example of lazy initializationint 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 initializationIn contrast, data from a data file is initialized while the .dat file is parsed and is allocatedmemory whether it is used by the model or not. In other words, external data is “pushed” toOPL.I L O G O P L D E V E L O P M E N T S T U D I O L A N G U A G ER E F E R E N C E M A N U A L53