Dang, someone wanting to replace C++ with J... I'd love to say you could do this, since I am a big fan of J, but if you need to squeeze the last bit of efficien

Dang, someone wanting to replace C++ with J... I'd love to say you could do this, since I am a big fan of J, but if you need to squeeze the last bit of efficiency out of a machine on a problem that can't be parallelized, C++ is probably a pretty good idea. If the "expensive in write time" logic isn't expensive in calculation time, you could wrap the expensive pieces in some verbs which call out to C. I'm often surprised though; a naive implementation of wavelets in J was quite comparable in runtime performance to a naive implementation of wavelets in C.