Fixes for handing of popcnt and for compilation on non-x86 architectures

LICENSE

@@ -1,6 +1,8 @@
 The MIT License (MIT)
 
+Copyright (c) 2013-2018 Ronald de Man
 Copyright (c) 2015 basil00
+Copyright (c) 2016-2024 by Jon Dart
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

Makefile

@@ -0,0 +1,34 @@
+MKDIR_P = mkdir -p
+RM      = rm
+INSTALL = install
+
+CC     ?= gcc
+CFLAGS  = -std=gnu99 -O2 -Wall -Wshadow -Isrc
+LDFLAGS = $(CFLAGS)
+
+PREFIX  = /usr/local
+LIBDIR  = $(PREFIX)/lib64
+INCDIR  = $(PREFIX)/include
+
+libfathom.so: obj/tbprobe.o
+	$(CC) $(LDFLAGS) -shared $^ -o $@
+
+obj/tbprobe.o: src/tbprobe.c src/tbchess.c src/stdendian.h src/tbprobe.h
+	@$(MKDIR_P) obj
+	$(CC) $(CFLAGS) -fPIC -c $< -o $@
+
+clean:
+	$(RM) -f libfathom.so
+	$(RM) -rf obj
+
+install: libfathom.so
+	$(MKDIR_P) $(DESTDIR)$(LIBDIR)
+	$(MKDIR_P) $(DESTDIR)$(INCDIR)
+	$(INSTALL) -m 0644 libfathom.so $(DESTDIR)$(LIBDIR)
+	$(INSTALL) -m 0644 src/{stdendian,tbconfig,tbprobe}.h $(DESTDIR)$(INCDIR)
+
+uninstall:
+	$(RM) -f $(DESTDIR)$(LIBDIR)/libfathom.so
+	$(RM) -f $(DESTDIR)$(INCDIR)/{stdendian,tbconfig,tbprobe}.h
+
+.PHONY: clean install uninstall

README.md

@@ -5,9 +5,22 @@ Fathom is a stand-alone Syzygy tablebase probing tool.  The aims of Fathom
 are:
 
 * To make it easy to integrate the Syzygy tablebases into existing chess
-  engines;
+  engines
 * To make it easy to create stand-alone applications that use the Syzygy
-  tablebases;
+  tablebases
+
+Fathom is compilable under either C99 or C++ and supports a variety of
+platforms, including at least Windows, Linux, and MacOS.
+
+Building the library
+--------------------
+It is possible to build and install Fathom as a shared library on Unix-like
+systems. Simply run the commands
+
+    make
+    make install
+
+in the top level directory.
 
 Tool
 ----
@@ -26,79 +39,112 @@ The tool will print out a PGN representation of the probe result, including:
 * WinningMoves: The list of all winning moves
 * DrawingMoves: The list of all drawing moves
 * LosingMoves: The list of all losing moves
-* A pseudo "principle variation" of Syzygy vs. Syzygy for the input position.
+* A pseudo "principal variation" of Syzygy vs. Syzygy for the input position.
 
 For more information, run the following command:
 
     fathom --help
 
-Pre-compiled versions of `fathom` (for all platforms) are available from here:
-
-* https://github.com/basil00/Fathom/releases
-
 Programming API
 ---------------
 
-Fathom provides a simple API.  There are three main function calls:
+Fathom provides a simple API. Following are the main function calls:
 
-* `tb_init` initializes the tablebase
-* `tb_probe_wdl` probes the Win-Draw-Loss (WDL) table for a given position
+* `tb_init` initializes the tablebases.
+* `tb_free` releases any resources allocated by Fathom.
+* `tb_probe_wdl` probes the Win-Draw-Loss (WDL) table for a given position.
 * `tb_probe_root` probes the Distance-To-Zero (DTZ) table for the given
-  position.
-
-All of the API functions use basic integer types, i.e. there is no need to
-create and initialize data-structures.  Fathom does not require the callee
-to provide any additional functionality (e.g. move generation) unlike the
-traditional `tbprobe` code.  However, chess engines can opt to replace some
-of the functionality of Fathom for better performance (see below).
-
-Chess Engines
+   position. It returns a recommended move, and also a list of unsigned
+   integers, each one encoding a possible move and its DTZ and WDL values.
+* `tb_probe_root_dtz` probes the Distance-To-Zero (DTZ) at the root position.
+   It returns a score and a rank for each possible move.
+* `tb_probe_root_wdl` probes the Win-Draw-Loss (WDL) at the root position.
+   it returns a score and a rank for each possible move.
+
+Fathom does not require the callee to provide any additional functionality
+(e.g. move generation). A simple set of chess-related functions including move
+generation is provided in file `tbchess.c`. However, chess engines can opt to
+replace some of this functionality for better performance (see below).
+
+Chess engines
 -------------
 
-Chess engines can be `tb_probe_wdl` to get the WDL value during search.  The
-`tb_probe_root` functional can be used to help pick the best move at the root.
-Note that `tb_probe_root` is slower and therefore should only be used at the
-root.
-
-Chess engines can opt for a tighter integration of Fathom by configuring
-`tbconfig.h`.  Specifically, the chess engines can define `TB_*_ATTACKS`
-macros that replace the default definitions with the engine's own definitions,
-avoiding duplication of functionality.
-
-Credits
--------
-
-The Syzygy tablebases were created by Ronald de Man.  Much of the probing code
-`tbprobe.c` is a modified version of Ronald's `tbprobe.cpp` for Stockfish (all
-Stockfish-specific code has been removed).  The `tbcore.c` file is virtually
-unchanged from Ronald's original version.
+Chess engines can use `tb_probe_wdl` to get the WDL value during
+search. This function is thread safe (unless TB_NO_THREADS is
+set). The various "probe_root" functions are intended for probing only
+at the root node, but are also theread-safe.
+
+Chess engines and other clients can modify some features of Fathom and
+override some of its internal functions by configuring
+`tbconfig.h`. `tbconfig.h` is included in Fathom's code with angle
+brackets. This allows a client of Fathom to override tbconfig.h by
+placing its own modified copy in its include path before the Fathom
+source directory.
+
+One option provided by `tbconfig.h` is to define macros that replace
+some aspects of Fathom's functionality, such as calculating piece
+attacks, avoiding duplication of functionality.  If doing this,
+however, be careful with including typedefs or defines from your own
+code into `tbconfig.h`, since these may clash with internal definitions
+used by Fathom. I recommend instead interfacing to external
+functions via a small module, with an interface something like this:
+
+```
+#ifndef _TB_ATTACK_INTERFACE
+#define _TB_ATTACK_INTERFACE
+
+#ifdef __cplusplus
+#include <cstdint>
+#else
+#include <stdint.h>
+#endif
+
+extern tb_knight_attacks(unsigned square);
+extern tb_king_attacks(unsigned square);
+extern tb_root_attacks(unsigned square, uint64_t occ);
+extern tb_bishop_attacks(unsigned square, uint64_t occ);
+extern tb_queen_attacks(unsigned square, uint64_t occ);
+extern tb_pawn_attacks(unsigned square, uint64_t occ);
+
+#endif
+```
+
+You can add if wanted other function definitions such as a popcnt
+function based on the chess engine's native popcnt support.
+
+`tbconfig.h` can then reference these functions safety because the
+interface depends only on types defined in standard headers. The
+implementation, however, can use any types from the chess engine or
+other client that are necessary. (A good optimizer with link-time
+optimization will inline the implementation code even though it is not
+visible in the interface).
+
+History and Credits
+-------------------
+
+The Syzygy tablebases were created by Ronald de Man. The original version of Fathom
+(https://github.com/basil00/Fathom) combined probing code from Ronald de Man, originally written for
+Stockfish, with chess-related functions and other support code from Basil Falcinelli.
+That codebase is no longer being maintained. This repository was originaly a fork of
+that codebase, with additional modifications by Jon Dart.
+
+However, the current Fathom code in this repository is no longer
+derived directly from the probing code written for Stockfish, but
+instead derives from tbprobe.c, which is a component of the Cfish
+chess engine (https://github.com/syzygy1/Cfish), a Stockfish
+derivative. tbprobe.c includes 7-man tablebase support. It was written
+by Ronald de Man and released for unrestricted distribution and use.
+
+This fork of Fathom replaces the Cfish board representation and move
+generation code used in tbprobe.c with simpler, MIT-licensed code from the original
+Fathom source by Basil. The code has been reorganized so that
+`tbchess.c` contains all move generation and most chess-related typedefs
+and functions, while `tbprobe.c` contains all the tablebase probing
+code. The code replacement and reorganization was done by Jon Dart.
 
 License
 -------
 
-(C) 2013-2015 Ronald de Man (original code)
-(C) 2015 basil (new modifications)
-
-Ronald de Man's original code can be "redistributed and/or modified without
-restrictions".
-
-The new modifications are released under the permissive MIT License:
-
-Permission is hereby granted, free of charge, to any person obtaining a copy of
-this software and associated documentation files (the "Software"), to deal in
-the Software without restriction, including without limitation the rights to
-use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
-of the Software, and to permit persons to whom the Software is furnished to do
-so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.
+This version of Fathom is released under the MIT License. See the LICENSE file for
+details.
 

src/apps/Makefile

@@ -5,9 +5,9 @@ endif
 ifeq ($(UNAME),Darwin)
     TARGET=fathom.macosx
 endif
-CC=clang
+CC?=gcc
 STRIP=strip
-CFLAGS=-std=gnu99 -O2 -Wall -D TB_NO_THREADS -D TB_NO_HW_POP_COUNT -I..
+CFLAGS=-std=gnu99 -O2 -Wall -Wshadow -DTB_NO_THREADS -I..
 
 main: $(TARGET)