For example , if we are running code on a 2-processor system ( CPUs A and B ) in a parallel computing environment , and we want to do a task on some data D , it is possible to tell CPU A to do that task on one part of D and CPU B on another part of D simultaneously ( at the same time ) , in order to reduce the runtime of the execution . For instance , consider a 2-processor system ( CPUs A and B ) in a parallel environment , and we wish to do a task on some data . It is possible to tell CPU A to do that task on one part of and CPU B on another part simultaneously , thereby reducing the duration of the execution .