question: public static Resource computeTotalResourceChange ( TopologyAPI . Topology topology , Map < String , Integer > componentChanges , Resource defaultInstanceResources , ScalingDirection scalingDirection ) { double cpu = 0 ; long ram = 0 ; long disk = 0 ; Map < String , Long > ramMap = TopologyUtils . getComponentRamMapConfig ( topology ) ; Map < String , Integer > componentsToScale = PackingUtils . getComponentsToScale ( componentChanges , scalingDirection ) ; for ( String component : componentsToScale . keySet ( ) ) { int parallelismChange = Math . abs ( componentChanges . get ( component ) ) ; cpu += parallelismChange * defaultInstanceResources . getCpu ( ) ; disk += parallelismChange * defaultInstanceResources . getDisk ( ) ; if ( ramMap . containsKey ( component ) ) { ram += parallelismChange * ramMap . get ( component ) ; } else { ram += parallelismChange * defaultInstanceResources . getRam ( ) ; } } return new Resource ( cpu , ram , disk ) ; }
target:  Identifies the resources reclaimed by the components that will be scaled down