> I think you misunderstood codedivine. His point was not that applications that use STM and make use of a single thread are slower than sequential implementations of the same application.

And the experience has been exactly the same in locks-based GIL-removal tests in Python: David Beazley recently "unearthed" and tested a GIL-removal patch from the 1.4 days[0]...

> To test threads, I wrote a small sample that subdivided the work across two worker threads is an embarrassingly parallel manner (note: this code is a little wonky due to the fact that Python-1.4 doesn't implement thread joining--meaning that you have to do it yourself with the included binary-semaphore lock).

> [...]

> If you run this code with the GIL, the execution time is about 2.5 seconds or approximately 1.3 times slower than the single-threaded version (1.9 seconds). Using the GIL-less Python, the execution time is 18.5 seconds or approximately 1.45 times slower than the single-threaded version (12.7 seconds). Just to emphasize, the GIL-less Python running with two-threads is running more than 7 times slower than the version with a GIL.

[0] http://dabeaz.blogspot.com/2011/08/inside-look-at-gil-remova...