Small speed improvements

benchmark                  old ns/op    new ns/op    delta
BenchmarkWordsDecode1e3         9490         9487   -0.03%
BenchmarkWordsDecode1e4        96773        96801   +0.03%
BenchmarkWordsDecode1e5      1005181      1005075   -0.01%
BenchmarkWordsDecode1e6      9267462      9273850   +0.07%
BenchmarkWordsEncode1e3        16890        16329   -3.32%
BenchmarkWordsEncode1e4       143161       138926   -2.96%
BenchmarkWordsEncode1e5      1503192      1454598   -3.23%
BenchmarkWordsEncode1e6     12707867     12481181   -1.78%
Benchmark_UFlat0              431901       431704   -0.05%
Benchmark_UFlat1             3973120      3975975   +0.07%
Benchmark_UFlat2               35847        36110   +0.73%
Benchmark_UFlat3              144321       144520   +0.14%
Benchmark_UFlat4             1052956      1053473   +0.05%
Benchmark_UFlat5              157574       157537   -0.02%
Benchmark_UFlat6               77308        77294   -0.02%
Benchmark_UFlat7               25250        25250   +0.00%
Benchmark_UFlat8             6569766      6571532   +0.03%
Benchmark_UFlat9             1405489      1404630   -0.06%
Benchmark_UFlat10            1206250      1205543   -0.06%
Benchmark_UFlat11            3786819      3785146   -0.04%
Benchmark_UFlat12            4963379      4959895   -0.07%
Benchmark_UFlat13            1846102      1845247   -0.05%
Benchmark_UFlat14             264426       264340   -0.03%
Benchmark_UFlat15              31943        31946   +0.01%
Benchmark_UFlat16             418485       418417   -0.02%
Benchmark_UFlat17            1327690      1327488   -0.02%
Benchmark_ZFlat0              573266       571356   -0.33%
Benchmark_ZFlat1             6993135      6428089   -8.08%
Benchmark_ZFlat2             1287888       899989  -30.12%
Benchmark_ZFlat3              890052       676929  -23.95%
Benchmark_ZFlat4             1088903      1188597   +9.16%
Benchmark_ZFlat5              274841       256050   -6.84%
Benchmark_ZFlat6              112702       109099   -3.20%
Benchmark_ZFlat7               40879        38929   -4.77%
Benchmark_ZFlat8             8072023      7994052   -0.97%
Benchmark_ZFlat9             2087487      2000266   -4.18%
Benchmark_ZFlat10            1836140      1749272   -4.73%
Benchmark_ZFlat11            5579367      5374859   -3.67%
Benchmark_ZFlat12            7447378      7123935   -4.34%
Benchmark_ZFlat13            2395367      2404353   +0.38%
Benchmark_ZFlat14             438720       411076   -6.30%
Benchmark_ZFlat15              54808        51187   -6.61%
Benchmark_ZFlat16             553975       556510   +0.46%
Benchmark_ZFlat17            1605651      1618518   +0.80%

benchmark                   old MB/s     new MB/s  speedup
BenchmarkWordsDecode1e3       105.37       105.40    1.00x
BenchmarkWordsDecode1e4       103.33       103.30    1.00x
BenchmarkWordsDecode1e5        99.48        99.50    1.00x
BenchmarkWordsDecode1e6       107.90       107.83    1.00x
BenchmarkWordsEncode1e3        59.21        61.24    1.03x
BenchmarkWordsEncode1e4        69.85        71.98    1.03x
BenchmarkWordsEncode1e5        66.53        68.75    1.03x
BenchmarkWordsEncode1e6        78.69        80.12    1.02x
Benchmark_UFlat0              237.09       237.20    1.00x
Benchmark_UFlat1              176.71       176.58    1.00x
Benchmark_UFlat2             3541.65      3515.83    0.99x
Benchmark_UFlat3              653.61       652.71    1.00x
Benchmark_UFlat4              389.00       388.81    1.00x
Benchmark_UFlat5              156.14       156.17    1.00x
Benchmark_UFlat6              144.23       144.25    1.00x
Benchmark_UFlat7              147.36       147.36    1.00x
Benchmark_UFlat8              156.74       156.70    1.00x
Benchmark_UFlat9              108.21       108.28    1.00x
Benchmark_UFlat10             103.78       103.84    1.00x
Benchmark_UFlat11             112.69       112.74    1.00x
Benchmark_UFlat12              97.08        97.15    1.00x
Benchmark_UFlat13             278.00       278.13    1.00x
Benchmark_UFlat14             144.61       144.66    1.00x
Benchmark_UFlat15             132.33       132.31    1.00x
Benchmark_UFlat16             283.37       283.42    1.00x
Benchmark_UFlat17             138.83       138.85    1.00x
Benchmark_ZFlat0              178.63       179.22    1.00x
Benchmark_ZFlat1              100.40       109.22    1.09x
Benchmark_ZFlat2               98.58       141.07    1.43x
Benchmark_ZFlat3              105.98       139.35    1.31x
Benchmark_ZFlat4              376.16       344.61    0.92x
Benchmark_ZFlat5               89.52        96.09    1.07x
Benchmark_ZFlat6               98.93       102.20    1.03x
Benchmark_ZFlat7               91.02        95.58    1.05x
Benchmark_ZFlat8              127.57       128.81    1.01x
Benchmark_ZFlat9               72.86        76.03    1.04x
Benchmark_ZFlat10              68.18        71.56    1.05x
Benchmark_ZFlat11              76.49        79.40    1.04x
Benchmark_ZFlat12              64.70        67.64    1.05x
Benchmark_ZFlat13             214.25       213.45    1.00x
Benchmark_ZFlat14              87.16        93.02    1.07x
Benchmark_ZFlat15              77.12        82.58    1.07x
Benchmark_ZFlat16             214.07       213.09    1.00x
Benchmark_ZFlat17             114.79       113.88    0.99x