In Grasshopper, solutions refer both to the computed data associated with a specific file and the process of computing that data. Whenever a file is modified, e.g. by adding or removing a component, by creating or deleting a wire, or by modifying the state of an existing component, the current solution expires and the calculations required for the new solution begin. It may take an exceedingly long time to complete a solution—minutes, or in extreme cases even hours—and during this update process the old expired solution will remain loaded.