The daily work on Truffle compiler team and the time I got when traveling from Snowcamp at Grenoble gave me a chance to speed Bck2Brwsr up. The sieve being a nice - e.g. small and focused - benchmark. Originally the algorithm couldn't be finished in a reasonable time when running on old version of Bck2Brwsr, but knowing what optimizing compilers seek for, it was relatively easy to speed it up ten times.
With great pleasure I announce that Bck2Brwsr, the most complete Java VM in browser (that can run Javac as shown by Dew project) has been sped up many times being at most three times slower than HotSpot. Given the primary goal of Bck2Brwsr is modularity and not speed, I consider it a good sped up even knowing there is a room to make it even faster.
Enjoy the Bck2Brwsr 0.17's speed!