<email@example.com>was added. Here is what he wrote about it:
Caching is turned on by running waisserver with the flag -cachesyn.
For those of you who have fairly large synonym files (> 10Kb) and are running the software on a machine that supports shared memory (all the UNIX boxes that I have worked with do now), enabling this feature will speed up the waisserver response time by a significant factor.
For those of you who do not have shared memory, I have rewritten the memory allocation part of synonym.c so that bigger memory chunks are allocated and used rather than allocating memory for each word and synonym, so the code should be a little faster for you too.
You can find a brief explanation of how caching works in the header of synonym.c.