Thanks for all the helpful replies. Ken thanks for the timing results. I agree with you that it doesn't make sense if it takes liblouis 15 minutes rather than a few seconds to translate a file with around 100,000 words. However, it's hard to guess what the problem is without using a sophisticated profiler.
From what I've read and also in my own experience the biggest leverage for performance comes from using optimal algorithms. Interpreters, compilers, operating systems and hardware are getting faster all the time and, of course, computer memory continues to get larger and cheaper. For this reason, I think a discussion of algorithms is essential when planning for the future.
A very simple example where a choice of algorithms is possible occurs in braille translators that look up words in a provided list of translations and, if the word isn't found, translate it using a translation table. If using a list is faster that would suggest that a modification that adds each newly translated word to the list would be faster than retranslating it each time is encountered.
Susan For a description of the software, to download it and links to project pages go to http://www.abilitiessoft.com
