README for Yap 4.3 This directory contains a release of the Yap 4.2 Prolog system, originally developed at the Universidade do Porto by Luis Damas and Vitor Santos Costa, with contributions from the Edinburgh Prolog library, the C-Prolog manual authors, Ricardo Rocha, and many others. You should read the rest of this file for information on what Yap is and for instructions on how to build it. YAP 4.2 is known to build with many versions of gcc (<= gcc-2.7.2, >= gcc-2.8.1, >= egcs-1.0.1, gcc-2.95.*) and on a variety of Unix'es: SunOS 4.1, Solaris 2.*, Irix 5.2, HP-UX 10, Dec Alpha Unix, Linux 1.2 and Linux 2.* (RedHat 4.0 through 5.2, Debian 2.*) in both the x86 and alpha platforms. It has been built on Windows NT 4.0 using Cygwin from Cygnus Solutions (see README.cygwin) and using Visual C++ 6.0. The overall copyright and permission notice for Yap4.2 can be found in the Artistic file in this directory. Yap follows the Perl Artistic license, and it is thus non-copylefted freeware. The Yap distribution contains copylefted free software under the LGPL from Universidade Politecnica de Madrid, software from the Austrian Research Institute for Artificial Intelligence (OFAI) under the OFAI license, and software from Ludwig-Maximilians-Universitaet Muenchen (LMU) under the LMU license. We would like to take the opportunity to thank the developers of these packages for their kindness in allowing YAP to distribute these packages. If you have a question about this software, desire to add code, found a bug, want to request a feature, or wonder how to get further assistance, please send e-mail to yappers@ncc.up.pt. To subscribe to the mailing list, send a request to majordomo@ncc.up.pt with body "subscribe yappers". Online documentation is available for Yap at: http://www.ncc.up.pt/~vsc/Yap/ Recent versions of Yap, including both source and selected binaries, can be found from this same URL. 1. What is YAP The Yap Prolog System is a high-performance Prolog compiler developed at LIACC, Universidade do Porto. Yap provides several important features: o speed: Yap is widely considered one of the fastest available Prolog systems. o functionality: it supports stream I/O, sockets, modules, exceptions, Prolog debugger, C-interface, dynamic code, internal database, DCGs, saved states, co-routining, arrays. o we explicitly allow both commercial and non-commercial use of Yap. Yap is based on the David H. D. Warren's WAM (Warren Abstract Machine), with several optimizations for better performance. Yap follows the Edinburgh tradition, and was originally designed to be largely compatible with DEC-10 Prolog, Quintus Prolog, and especially with C-Prolog. Yap implements most of the ISO-Prolog standard. We are striving at full compatibility, and the manual describes what is still missing. The manual also includes a (largely incomplete) comparison with SICStus Prolog. 2. How to compile YAP If you are compiling YAP under VisualC++ look at README.VC. To compile YAP just do: (1) mkdir arch (2) cd arch (3) ../configure (4) check the Makefile for any extensions or changes you want to make. (5) make (6) If the compilation succeeds, try ./yap (7) Happy? make install (8) "make install-info" will create the info files in the standard info directory. (9) "make html" will create documentation in html format in the current directory. In most systems you will need to be superuser in order to do "make install" and "make info" on the standard directories. 2.1 Where to install Yap YAP uses autoconf. Recent versions of Yap try to follow GNU conventions on where to place software. o The main executable is placed at BINDIR. This executable is actually a script that calls the Prolog engine, stored at YAPLIBDIR. o LIBDIR is the directory where libraries are stored. YAPLIBDIR is a subsdirectory that contains the Prolog engine and a Prolog library. o INCLUDEDIR is used if you want to use Yap as a library. o INFODIR is where the info help files will be stored. Usually /usr/local/info, /usr/info, or /usr/share/info. 2.2 Which Yap to compile Compiling Yap with the standard options give you a plain vanilla Prolog. You can tune Yap to use extra functionality by using the following options to configure: o --enable-rational-trees=yes gives you support for infinite rational trees. o --enable-coroutining=yes gives you support for coroutining, including freezing of goals, attributed variables, and constraints. This will also enable support for infinite rational trees. o --enable-depth-limit=yes allows depth limited evaluation, say for implementing iterative deepening. o --enable-low-level-tracer=yes allows support for tracing all calls, retries, and backtracks in the system. This can help in debugging your application, but results in performance loss. o --enable-wam-profile=yes allows profiling of abstract machine instructions. This is useful when developing YAP, should not be so useful for normal users. o --enable-parallelism={env-copy,sba,a-cow} allows or-parallelism supported by one of these three forms. This is still highly experimental. o --enable-tabling={local,batched} allows one of the two forms of tabling. This is still experimental. 2.3 Porting Yap The system has been mainly tested with GCC, but we have been able to compile versions of Yap under lcc in Linux, Sun's cc compiler, IBM's xlc, SGI's cc, and Microsoft's Visual C++ 6.0. The HP-UX cc preprocessor is known to choke under Yap. 2.3.1 Yap and GCC Yap has been developed to take advantage of GCC (but not to depend on it). The major advantage of GCC is threaded code and register reservation. YAP is set by default to compile with the best compilation flags we know. Even so, a few specific options can be used depending on the architecture: 2.3.1.1 x86 The flag: YAP_EXTRAS= ... -DBP_FREE=1 tells us to use the %bp register (frame-pointer) as the emulator's program counter. This seems to be stable and should become default real soon now. 2.3.1.2 Sparc/Solaris2 Use: YAP_EXTRAS= ... -mno-app-regs -DOPTIMISE_ALL_REGS_FOR_SPARC=1 and YAP will get two extra registers! This trick does not work on SunOS 4 machines. 2.3.1.3 Tuning GCC/Yap for your machine model Versions of GCC can be tweaked for different processors, eg, 486, Pentium, PentiumPro, Ultrasparc, Supersparc. Unfortunately, some of these tweaks do may make Yap run slower or not at all in other machines with the same instruction set, so they cannot be made default. The best options also depends on the version of GCC you are using, and it is a good idea to consult the GCC manual under the menus "Invoking GCC"/"Submodel Options". We next describe a few: (a) GCC up to 2.7.*: o 486: YAP_EXTRAS= ... -m486 -DBP_FREE=1 to take advantage of 486 specific optimisations in GCC 2.7.*. o Pentium: YAP_EXTRAS= ... -m486 -malign-loops=2 -malign-jumps=2 -malign-functions=2 o PentiumPros are known not to require alignment. o Super and UltraSparcs: YAP_EXTRAS= ... -msupersparc (b) GCC 2.8.*, EGCS, GCC 2.95.* o Check -march=XXX for fun.