One thread:
1024000 numbers: 191 ms
2048000 numbers: 380 ms
8192000 numbers: 1638 ms
Two threads:
1024000 numbers: 112 ms
2048000 numbers: 252 ms
8192000 numbers: 953 ms
Four threads:
1024000 numbers: 83 ms
2048000 numbers: 167 ms
8192000 numbers: 672 ms