Dang, someone wanting to replace C++ with J... I&#x27;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&#x27;t be parallelized, C++ is probably a pretty good idea. If the &quot;expensive in write time&quot; logic isn&#x27;t expensive in calculation time, you could wrap the expensive pieces in some verbs which call out to C.<p>I&#x27;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.