SOFTWARE DESIGN OF LANDIS 4.0

LANDIS 4.0 is a new generation program based on earlier versions of LANDIS (Mladenoff and He 1999). LANDIS 4.0 uses a component-based approach to conduct simulation, which breaks the monolithic program into multiple small, stand-alone, and functionally more specific components (He et al. 2002).

A component in a model is like a mini-model; it comes packaged as a binary code that is compiled, linked, and ready to perform certain tasks for the entire model. Components connect with each other at run time to form a complete model. With a component-based model, it is possible to replace some components while maintaining the integrity of the model. In LANDIS 4.0, each component (module) simulates a particular process and collectively they simulate forest landscape change under natural and anthropogenic disturbances.

Breaking up a single monolithic program into several logically independent modules has following advantages (He et al. 2002): 1) modifying and testing a component is a much smaller task than tackling a whole model; 2) keeping the logic of an ecological process contained within a single module ensures that changes to a module will not have unintended effects in other parts of the model; 3) components can be developed by different groups or in other programming languages; 4) upgrading the model is easier because existing components can easily be replaced by new components. This reduces the number of largely redundant versions of the model and allows the modeling community to focus on significant conceptual advances rather than managing cumbersome code. These advantages truly allow more groups to participate in the modeling work. For example, a disturbance may have several designs and implementations from different groups in the dynamically linked libraries format, which can be plugged into LANDIS 4.0 and run without recoding and recompiling the whole model. This provides an ideal platform for scientists to compare and analyze different disturbance module designs. Therefore, a component-based model can be more rigorously tested, evaluated, and modified than a monolithic model, and these processes can be conducted not only by the original developers, but by the larger modeling community (He et al. 2002).

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