CMP.10:4.4 - Count the complete computation under an explicit cost model

Compare construction and conversion, the intended reads and updates, reconstruction or output, and peak storage. A useful first comparison is construction cost + sum of operation costs for the workload. Keep several resource dimensions separate when no accepted trade-off combines them.

State what one elementary operation costs. Arithmetic on a bounded machine word can be treated as constant in an appropriate model; multiplying or comparing integers whose encoded lengths grow needs the corresponding bit cost. A symbolic expression that shares subexpressions can be small while its fully expanded output is large.

If transfers between memory levels dominate, analyze blocks moved as well as abstract pointer or arithmetic operations. A representation with contiguous access can outperform one with fewer but scattered accesses. Realization measurements can distinguish close candidates; they need not precede a decision already settled by an adequate cost argument.

Include invalidation and synchronization when shared updates are part of the workload. An operation that is correct in sequential use does not acquire a concurrent guarantee merely because its representation is shared.