Leo Hsu and Regina Obe: Writing PostGIS raster Map Algebra Callback Functions in PL/V8

I've read from many that PL/V8 mathematic operations are generally faster than what you get with SQL functions and PL/pgsql functions. One area where I thought this speed would be really useful was for writing Map Algebra call-back functions. A PostGIS 2.1+ map algebra callback function signature looks like: func_name(double precision[][][] value, integer[][] pos, text[] VARIADIC userargs)