Benchmark: timing 10 iterations of AssembleByArray, AssembleByHash...
AssembleByArray: 10 wallclock secs ( 9.64 usr +  0.04 sys =  9.68 CPU) @  1.03/s (n=10)
AssembleByHash:  1 wallclock secs ( 1.31 usr +  0.00 sys =  1.31 CPU) @  7.63/s (n=10)
                  Rate AssembleByArray  AssembleByHash
AssembleByArray 1.03/s              --            -86%
AssembleByHash  7.63/s            639%              --