Som v 4.2

This is a small experiment on lex. Lex is implemented as a built-in function (via syscall 16). The hope is that this will accelerate the compiler.

lex2.c is written based on token-s.txt (lex in Som). An experimental version is lex0.c. It has a better buffering. However, it is more complex. lex0.c uses buffering to reduce the number of fread() call. lex2.c reads one line at a time.

It is quite interesting to see how the new lex is interfaced to the old token-s.txt in a simple way.

Note: the interactive mode does not work. Only compile and run is available at present (due to some bugs in lex on stdin).

Performance measurement

compiling som v3.1 (as a benchmark)

noi runtime (ms)

v41 4798780 266

v42 3757236 265

therefore, noi v42/v41 = 0.78, 1-v42/v41 = 0.22 (or 22% faster)

but the actual running time is the same. (running time is measured on Hp n6400, core 2 duo, 2 GHz)

Also this release celebrate the triple 9, ie. 9 September 2009 or 9/9/2009.

9/9/2009