1. A method for tracking the stability of a data set for multiple observers comprising: accessing a data set for use by a code, the code to modify the data set and to use data in the data set to obtain a result for a calculation; determining whether the data set is modified by the code; in the event the data set is modified by the code: setting a current data set tracker to a value, the value indicating only that the data set has been modified; and in the event the data set is not modified by the code: comparing a stored data set tracker value with the current data set tracker value; determining the stored data set tracker value is the same as the current data set tracker value; and using a cached result previously calculated by the code as the result for the calculation instead of recalculating the result.