_______ _______ __ _ ______ |______ | |______ | \ | | ____ | |_____ |______ | \_| |_____| Version: 17 I. Introduction This software is an implementation of "FLENG", a low level concurrent logic programming language descended from Prolog. A compiler is provided to translate programs written in FLENG into assembly language which can subsequently be compiled and linked into a binary executable. As FLENG is quite minimal in features, translators from "Flat Guarded Horn Clauses", "Strand" and "PCN" (other, higher- level concurrent logic languages) into FLENG are also available. FLENG programs allow for massive parallelism at a very fine grained level - goals are executed concurrently and communicate solely via single-assignment logic variables. The use of logic variables for inter-process communication offers an easy to use and convenient abstraction to implement many common patterns of synchronization and message passing in a natural manner. This implementation additionally can distribute pools of parallel processes over native OS level threads, thus taking advantage of multicore architectures. Locking overhead should be small, as data is normally not shared among processes executing on different threads. Automatic management of memory is provided using a reference-counting scheme of fixed size cells, which avoid fragmentation, avoids garbage collection pauses and keeps the overall memory required to hold live data at any point of time minimal, while providing relatively good locality. Interfacing to native code is straightforward and compiled FLENG code and the run time library support can be linked with other modules written in C or C++ without problems. The compilation tools allow cross compilation, provided the architecture is supported. The compiler generates native code, but does currently not perform a lot of optimizations, so performance-sensitive code should probably be written in C or another language. FLENG is particularly well suited as a coordination language for providing intercommunication and synchronization with reasonable overhead while calling out to C or C++ code for low-level or speed-critical operations. Suggestions for improvement or patches providing enhancements and corrections are very welcome, see the user's manual for information on how to contact the author. This software was written by Felix L. Winkelmann and has been released into the public domain. See the file "doc/LICENSE" for more information. A git[4] repository containing the sources can be found at the projects gitlab site[5]. II. Build and Installation * Requirements: The run-time system for FLENG is written in C99 with GNU extensions and should be compilable with most C compilers. The FGHC-to-FLENG and PCN-to-FLENG translators and the FLENG compiler are written in FGHC and require either a set of precompiled assembler files (included in the distribution tarball), a previously built FLENG system or a Prolog implementation that can be used to bootstrap the system. Currently, SWI[1] Prolog , GNU[2] Prolog and YAP[3] are supported. You additionally need a POSIX compliant sh(1) and optionally make(1) (GNU or BSD). The system is known to run on Linux and BSD-based UNIX systems. Supported target architectures are x86-64 armv6 (hardfp), AArch64, Apple M1 and riscv64 (R64IMAFD). Note that RISCV support is experimental and likely to be incomplete. If you are interested in ports to other platforms, please contact me. Support for graphical applications is provided by libraries interfacing to SDL2[6]. If available on the installation system, these libraries will be built and added to the module library. A higher level structured graphics toolkit with a design based on Joel Bartletts "EZDraw" system[7] provides more convenient means for programming graphical applications and is built on top of the SDL interface. At least SDL2 and SDL2_image are needed for graphics programming, SDL2_ttf and SDL2_mixer are optional. If these can't be found during the configuration phase of the build, then the system falls back on a built-in 16x8 bitmap font and font and sound-related operations silently fail. * Configuration: First run the "configure" shell script, optionally providing arguments. Enter ./configure --help to see a list of options for specifying the installation location and possibly selecting the host Prolog implementation to use. By default, the system will be installed in "/usr/local" and use GNU Prolog, if found, or, alternatively SWI Prolog. "configure" adds the contents of the environment variables "CC", "CFLAGS" and "LDFLAGS" to the default compiler and linker invocations, if set. If the libraries for graphics support are not required, pass the "--disable-sdl" option to the invocation of "configure". * Building: Once configuration has been done, you can run make(1) to build the compiler and run-time system. If you build directly from the sources of the development repository[5], you should first run make spotless to ensure no old translated files from previous check outs pollute the build. First, run make If no errors occur, you can optionally enter make check to run the test suite. make bench Runs a number of test programs and measures their run time. When building from a distribution tarball, the system is usually directly generated from precompiled assembler files. by entering make bootstrap you will force a bootstrap from the baseline Prolog compiler. A suitable Prolog system will be searched, you can override the automatic search by using the "--with-prolog" option for the "configure" script, giving it the full path to the Prolog compiler intended to use for bootstrapping. Building the system in a different directory than the one containing the source code is possible: mkdir build cd build /configure make By setting the environment variable "FLENG_PREFIX" to the current working directory, you can use the generated "fleng" driver script in-place to use or test the system without installation. * Installation: To install, enter make install If you do not have permissions to access the installation location, use sudo(1) or doas(1) when invoking "make install". The variable "$DESTDIR" will be respected when defined to further customize the installation destination. The following files will be installed: $PREFIX defaults to /usr/local |-- bin | |-- fghc2fl FHGC->FLENG compiler | |-- pcn2fl PCN->FLENG compiler | |-- fl2 FLENG->assembler compiler | `-- fleng driver script |-- include | |-- fleng-util.h utility header for C extensions | |-- fleng.h main header for C extensions | `-- pcn.h default include file for PCN code |-- share | |-- doc | | `-- fleng | | |-- MANUAL user's manual | | |-- INTERNALS documentation on some internals | | |-- LIBRARY documentation for all libraries | | |-- README this document | | |-- LICENSE license | | `-- DOCDB "flengdoc" database | | `-- ... | `-- man | |-- man1 | | |-- fleng.1 manual page for driver script | | `-- flengdoc.1 manual page for documentation tool | `-- man7 | |-- fleng.7 manual page for runtime options | `-- flengdoc.7 manual page describing documentation format `-- lib `-- libfleng.a FLENG runtime library III. Documentation The documentation is available in textual form in the files "doc/MANUAL", "LIBRARY" and "doc/INTERNALS". The "flengdoc" tool can be used to query the documentation reference database, which is created and installed along with the rest of the system. See man flengdoc for more information. IV. Get into Contact In case you need help, have suggestions or ideas, please don't hesitate to contact the author at felix AT call-with-current-continuation DOT org There is the IRC channel "#fleng" on https://libera.chat/ where you can ask questions, suggest improvements or if you just want to chat. V. References [1] http://www.swi-prolog.org [2] http://www.gprolog.org [3] https://github.com/vscosta/yap [4] https://git-scm.com/ [5] https://gitlab.com/b2495/fleng [6] https://www.libsdl.org [7] https://archive.org/download/bitsavers_dectechrep_144635/WRL-91-6.pdf