1.3 Should you be Using SWI-Prolog?

There are a number of reasons why you better choose a commercial Prolog system, or another academic product:

• SWI-Prolog is not supported
  Although I usually fix bugs shortly after a bug report arrives, I cannot promise anything. Now that the sources are provided, you can always dig into them yourself.
• Memory requirements and performance are your first concerns
  A number of commercial compilers are more keen on memory and performance than SWI-Prolog. I do not wish to sacrifice some of the nice features of the system, nor its portability to compete on raw performance.
• You need features not offered by SWI-Prolog
  In this case you may wish to give me suggestions for extensions. If you have great plans, please contact me (you might have to implement them yourself however).

On the other hand, SWI-Prolog offers some nice facilities:

• Nice environment
  This includes `Do What I Mean', automatic completion of atom names, history mechanism and a tracer that operates on single key-strokes. Interfaces to standard Unix editors are provided, as well as a facility to maintain programs (see make/0).
• Very fast compiler
  The compiler handles about 100K bytes per second on a SPARC-II processor.
• Transparent compiled code
  SWI-Prolog compiled code can be treated just as interpreted code: you can list it, trace it, assert to or retract from it, etc. This implies you do not have to decide beforehand whether a module should be loaded for debugging or not. Also, performance is much better than the performance of most interpreters.
• Profiling
  SWI-Prolog offers tools for performance analysis, which can be very useful to optimise programs. Unless you are very familiar with Prolog and Prolog performance considerations this might be more helpful than a better compiler without these facilities.
• Flexibility
  SWI-Prolog allows for easy and flexible integration with C, both Prolog calling C functions as C calling Prolog predicates. SWI-Prolog is provided in source form, which implies SWI-Prolog can be linked in with another package. Command line options and predicates to obtain information from the system and feedback into the system are provided.
• Integration with PCE
  SWI-Prolog offers a tight integration to the Object Oriented Package for User Interface Development, called PCE Anjewierden & Wielemaker, 1989. PCE is now also available for the X Window System.