1. A method, comprising: performing by a computer: writing a value to a shared data object in memory, wherein the shared data object comprises a plurality of data elements whose values collectively represent the value written to the shared data object; determining whether said writing changed a summary value associated with the shared data object, wherein the summary value is dependent on a mathematical or logical combination of the values of the plurality of data elements; and in response to determining that said writing changed the summary value associated with the shared data object, modifying a value of a shared indicator object such that the modified value reflects the changed summary value.