From 388068bc1d06b5a5b2411a982398c48e2b79aadf Mon Sep 17 00:00:00 2001
From: Avril <flanchan@cumallover.me>
Date: Sun, 16 Apr 2023 04:55:31 +0100
Subject: [PATCH] exopt::util::leven_diff(): Added working levenshtein distance
 algorithm.
MIME-Version: 1.0
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Fortune for libexopt's current commit: Half blessing − 半吉
---
 .gitignore      |   4 +
 Makefile        | 234 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/leven.h | 143 +++++++++++++++++++++++++++++
 src/leven.cpp   |  12 +++
 4 files changed, 393 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 include/leven.h
 create mode 100644 src/leven.cpp

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..f30e0fb
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,4 @@
+obj/
+lib*.so
+lib*.a
+*.o
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..99955de
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,234 @@
+# Makefile template, generic for libraries (static + shared)
+PROJECT=exopt
+DEFAULT_NAMESPACE=exopt
+VERSION=0.0.0
+
+SRC_C   = $(wildcard src/*.c)
+SRC_CXX = $(wildcard src/*.cpp)
+
+INCLUDE=include
+
+ifeq ($(PREFIX),)
+	PREFIX := /usr/local
+endif
+
+# Default archivers
+AR?=ar
+RANLIB?=ranlib
+
+# Use gcc-{ar,ranlib} when using gcc
+ifeq ($(CXX),g++)
+	AR=gcc-ar
+	RANLIB=gcc-ranlib
+endif
+
+# Link to these libraries dynamicalls
+SHARED_LIBS= 
+# Link to these libraries statically
+STATIC_LIBS=
+
+override __VERSION_SPLIT:= $(subst ., ,$(VERSION))
+override __VERSION_REVISION:=$(word 3,$(__VERSION_SPLIT)) 0
+
+VERSION_MAJOR:= $(word 1,$(__VERSION_SPLIT))
+VERSION_MINOR:= $(word 2,$(__VERSION_SPLIT))
+VERSION_BUGFIX:= $(word 3,$(__VERSION_SPLIT))
+VERSION_REVISION:= $(word 2,$(subst r, ,$(__VERSION_REVISION)))
+
+override __VERSION_SPLIT:= MAJOR:$(word 1,$(__VERSION_SPLIT)) MINOR:$(word 2,$(__VERSION_SPLIT)) BUGFIX:$(word 1,$(subst r, ,$(__VERSION_REVISION))) REVISION:$(word 2,$(subst r, ,$(__VERSION_REVISION))) REVISION_STRING:$(word 3,$(__VERSION_SPLIT))
+
+COMMON_FLAGS?= -W -Wall 
+COMMON_FLAGS+= -pipe -Wstrict-aliasing -fno-strict-aliasing $(addprefix -I,$(INCLUDE))
+COMMON_FLAGS+= $(addprefix -D_VERSION_,$(subst :,=,$(__VERSION_SPLIT))) '-D_VERSION="$(VERSION)"'
+
+ifneq ($(DEFAULT_NAMESPACE),)
+	COMMON_FLAGS+= '-D_DEFAULT_NS=$(DEFAULT_NAMESPACE)'
+endif
+
+## CPU feature flags
+CPU_FLAGS+=
+
+DEFINITIONS?=_IMPL
+
+COMMON_FLAGS+=$(addprefix -D,$(DEFINITIONS)) 
+COMMON_FLAGS+=$(addprefix -m,$(CPU_FLAGS))
+
+## For LTO and linking over all TUs in general
+BINFLAGS+=
+
+DEBUG_BINFLAGS+=
+RELEASE_BINFLAGS+= -fuse-linker-plugin
+
+# Target arch. Set to blank for generic
+ARCH?=native
+# Enable OpenMP and loop parallelisation? (dyn-links to openmp)
+PARALLEL?=yes
+
+OPT_FLAGS?= -fgraphite \
+	    -floop-interchange -ftree-loop-distribution -floop-strip-mine -floop-block \
+	    -fno-stack-check
+
+SHARED_FLAGS+=-fPIC
+SHARED_RELEASE_FLAGS+=
+SHARED_DEBUG_FLAGS+=
+
+STATIC_FLAGS+=
+STATIC_RELEASE_FLAGS+=-ffat-lto-objects
+STATIC_DEBUG_FLAGS+=
+
+ifneq ($(ARCH),)
+	OPT_FLAGS+= $(addprefix -march=,$(ARCH))
+endif
+
+ifeq ($(PARALLEL),yes)
+	SHARED_FLAGS+= -fopenmp 
+	SHARED_RELEASE_FLAGS+= -floop-parallelize-all -ftree-parallelize-loops=4
+endif
+
+CXX_OPT_FLAGS?= $(OPT_FLAGS) -felide-constructors
+
+CSTD?=gnu2x
+CXXSTD?=gnu++23
+
+CFLAGS   += $(COMMON_FLAGS) --std=$(CSTD)
+CXXFLAGS += $(COMMON_FLAGS) --std=$(CXXSTD)
+LDFLAGS  += $(addsuffix .a,$(addprefix -l:lib,$(STATIC_LIBS))) $(addprefix -l,$(SHARED_LIBS))
+
+STRIP=strip
+
+# TODO: XXX: Benchmark to see if `-fno-plt` actually helps... 
+RELEASE_COMMON_FLAGS+= -fno-plt -fno-bounds-check
+
+DEBUG_COMMON_FLAGS+= -ggdb -gz -ftrapv -fbounds-check
+# -fanalyzer
+
+ifneq ($(TARGET_SPEC_FLAGS),no)
+	RELEASE_CFLAGS?=  -O3 -flto $(OPT_FLAGS)
+	RELEASE_CXXFLAGS?= -O3 -flto $(CXX_OPT_FLAGS)
+	RELEASE_LDFLAGS?=  -Wl,-O3 -Wl,-flto
+
+	#SHARED_FLAGS+=$(SHARED_RELEASE_FLAGS)
+
+	DEBUG_CFLAGS?= -Og
+	DEBUG_CXXFLAGS?= -Og
+
+	DEBUG_LDFLAGS?=
+endif
+
+DEBUG_CFLAGS+=-DDEBUG $(DEBUG_COMMON_FLAGS)
+DEBUG_CXXFLAGS+=-DDEBUG $(DEBUG_COMMON_FLAGS) -fasynchronous-unwind-tables
+
+RELEASE_CFLAGS+=-DRELEASE $(RELEASE_COMMON_FLAGS)
+RELEASE_CXXFLAGS+=-DRELEASE $(RELEASE_COMMON_FLAGS)
+
+# Objects
+
+OBJ_C   = $(addprefix obj/c/,$(SRC_C:.c=.o))
+OBJ_CXX = $(addprefix obj/cxx/,$(SRC_CXX:.cpp=.o))
+OBJ = $(OBJ_C) $(OBJ_CXX)
+
+# Phonies
+
+.PHONY: release
+release: | dirs
+	$(MAKE) lib$(PROJECT).a
+	@$(MAKE) clean-rebuild >> /dev/null
+	@$(MAKE) dirs >> /dev/null
+	$(MAKE) lib$(PROJECT).so
+
+.PHONY: debug
+debug: | dirs
+	$(MAKE) lib$(PROJECT)-debug.a
+	@$(MAKE) clean-rebuild >> /dev/null
+	@$(MAKE) dirs >> /dev/null
+	$(MAKE) lib$(PROJECT)-debug.so
+
+# Rebuild both release and debug targets from scratch
+.PHONY: all
+all: | clean
+	@$(MAKE) release
+	@$(MAKE) clean-rebuild
+	@$(MAKE) debug
+
+.PHONY: install
+.PHONY: uninstall
+
+.PHONY: test
+test:
+	@rm -f $(PROJECT)-test
+	@$(MAKE) $(PROJECT)-test
+
+# Targets
+
+dirs:
+	@mkdir -p obj/c{,xx}/src{,/rng}
+
+obj/c/%.o: %.c
+	$(CC) -c $< $(CFLAGS) -o $@ $(LDFLAGS)
+
+obj/cxx/%.o: %.cpp
+	$(CXX) -c $< $(CXXFLAGS) -o $@ $(LDFLAGS)
+
+lib$(PROJECT)-release.a: CFLAGS+= $(RELEASE_CFLAGS) $(STATIC_FLAGS) $(STATIC_RELEASE_FLAGS)
+lib$(PROJECT)-release.a: CXXFLAGS += $(RELEASE_CXXFLAGS) $(STATIC_FLAGS) $(STATIC_RELEASE_FLAGS)
+lib$(PROJECT)-release.a: LDFLAGS += $(RELEASE_LDFLAGS)
+lib$(PROJECT)-release.a: $(OBJ)
+	$(AR) rcs $@ $^
+	$(RANLIB) $@
+
+lib$(PROJECT)-debug.a: CFLAGS+= $(DEBUG_CFLAGS) $(STATIC_FLAGS) $(STATIC_DEBUG_FLAGS)
+lib$(PROJECT)-debug.a: CXXFLAGS += $(DEBUG_CXXFLAGS) $(STATIC_FLAGS) $(STATIC_DEBUG_FLAGS)
+lib$(PROJECT)-debug.a: LDFLAGS += $(DEBUG_LDFLAGS)
+lib$(PROJECT)-debug.a: $(OBJ)
+	$(AR) rcs $@ $^ 
+	$(RANLIB) $@
+
+lib$(PROJECT)-release.so: CFLAGS+= $(RELEASE_CFLAGS) $(SHARED_FLAGS) $(SHARED_RELEASE_FLAGS)
+lib$(PROJECT)-release.so: CXXFLAGS += $(RELEASE_CXXFLAGS) $(SHARED_FLAGS) $(SHARED_RELEASE_FLAGS)
+lib$(PROJECT)-release.so: LDFLAGS += $(RELEASE_LDFLAGS)
+lib$(PROJECT)-release.so: BINFLAGS += $(RELEASE_BINFLAGS)
+lib$(PROJECT)-release.so: $(OBJ)
+	$(CXX) -shared $^ $(BINFLAGS) $(CXXFLAGS) -o $@ $(LDFLAGS)
+	$(STRIP) $@
+
+lib$(PROJECT)-debug.so: CFLAGS+= $(DEBUG_CFLAGS) $(SHARED_FLAGS) $(SHARED_DEBUG_FLAGS)
+lib$(PROJECT)-debug.so: CXXFLAGS += $(DEBUG_CXXFLAGS) $(SHARED_FLAGS) $(SHARED_DEBUG_FLAGS)
+lib$(PROJECT)-debug.so: LDFLAGS += $(DEBUG_LDFLAGS)
+lib$(PROJECT)-debug.so: BINFLAGS += $(DEBUG_BINFLAGS)
+lib$(PROJECT)-debug.so: $(OBJ)
+	$(CXX) -shared $^ $(BINFLAGS) $(CXXFLAGS) -o $@ $(LDFLAGS)
+
+lib$(PROJECT).a: lib$(PROJECT)-release.a
+	ln -f $< $@
+
+lib$(PROJECT).so: LDFLAGS+= -Wl,-soname,lib$(PROJECT).so.$(VERSION_MAJOR)
+lib$(PROJECT).so: lib$(PROJECT)-release.so
+	ln -f $< $@.$(VERSION)
+	ln -sf $@.$(VERSION) $@.$(VERSION_MAJOR)
+	ln -sf $@.$(VERSION_MAJOR) $@
+
+clean-rebuild:
+	rm -rf obj
+
+clean: clean-rebuild
+	rm -f lib$(PROJECT){,-{release,debug,pgo}}.{a,so{,.*}}
+	rm -f $(PROJECT)-test
+
+install:
+	install -d $(DESTDIR)$(PREFIX)/lib/
+	install -m 644 lib$(PROJECT).a $(DESTDIR)$(PREFIX)/lib/
+	install -s -m 755 lib$(PROJECT).so.$(VERSION) $(DESTDIR)$(PREFIX)/lib/
+	ln -sf lib$(PROJECT).so.$(VERSION) $(DESTDIR)$(PREFIX)/lib/lib$(PROJECT).so.$(VERSION_MAJOR)
+	ln -sf lib$(PROJECT).so.$(VERSION_MAJOR) $(DESTDIR)$(PREFIX)/lib/lib$(PROJECT).so
+	install -d $(DESTDIR)$(PREFIX)/include/$(PROJECT)/
+	install -m 644 $(wildcard $(INCLUDE)/*.*) $(DESTDIR)$(PREFIX)/include/$(PROJECT)/
+uninstall:
+	-rm $(DESTDIR)$(PREFIX)/lib/lib$(PROJECT).{a,so{,.*}}
+	cd $(INCLUDE) && find . -type f | xargs -I {} rm "$(DESTDIR)$(PREFIX)/include/$(PROJECT)/{}"
+	-rmdir $(DESTDIR)$(PREFIX)/include/$(PROJECT)
+
+$(PROJECT)-test: LDFLAGS+= -lfmt -lstdc++
+$(PROJECT)-test: CFLAGS+= -Og -g
+$(PROJECT)-test: lib$(PROJECT)-debug.a
+	$(CC) $(CFLAGS) src/test/*.c -o $@ -l:$< $(LDFLAGS)
+	-valgrind ./$@
diff --git a/include/leven.h b/include/leven.h
new file mode 100644
index 0000000..0eb26f8
--- /dev/null
+++ b/include/leven.h
@@ -0,0 +1,143 @@
+#ifndef _LEVEN_H
+#define _LEVEN_H
+
+#ifdef __cplusplus
+
+#include <string_view>
+#include <concepts>
+#include <vector>
+#include <span>
+#include <tuple>
+
+extern "C" {
+#endif
+
+#ifdef __cplusplus
+}
+
+namespace exopt { namespace util [[gnu::visibility("internal")]] {
+#if 0
+	void** allocate_array(size_t elem, size_t d1, size_t d2) [[gnu::returns_nonnull]];
+	void deallocate_array(void** array) noexcept;
+
+	/*constexpr auto min(auto const& a, auto const& b) noexcept
+		-> std::common_type_t<decltype(a), decltype(b)> 
+		 requires(requires(decltype(a) _a, decltype(b) _b) {
+		{ _a < _b } -> std::convertible_to<bool>;
+	}) {
+		return a < b ? a : b;
+	}*/
+
+	/// Compute the levenshtein distance.
+	constexpr auto leven_diff(std::convertible_to<std::string_view> auto const& a, std::convertible_to<std::string_view> auto const& b) noexcept {
+		std::string_view s = a,
+				t = b;
+		const signed long n = long(s.size());
+		const signed long m = long(t.size());
+
+		if(__builtin_expect(!n, 0)) return m;
+		if(__builtin_expect(!m, 0)) return n;
+
+		//constexpr 
+		auto&& work_on_d = [&](auto& d) {
+			for(long i=0; i <= n ; d[i][0] = i) i+=1;
+			for(long i=0; i <= m ; d[0][i] = i) i+=1;
+
+			for(long i=1; i <= n; i++) {
+				for(long j=1; j<=m; j++)
+				{
+					using std::min;
+					const auto cost = std::type_identity_t<signed long>(! (t[j-1] == s[i-1]));
+					d[i][j] = min(
+						min(d[i-1][j] + 1, d[i][j-1] + 1)
+						, d[i-1][j-1] + cost);
+				}
+			}
+			return d[n][m];
+		};
+		//TODO: XXX Multidimensional array not working... fuck THIS
+		if consteval {
+			using Vec2 = std::vector<std::vector<signed long>>;
+			struct vec : public Vec2 ///TODO: XXX: best way to do this? We just want the `d`` ctor overload...
+			{
+//TODO: for below ctor of inner (size_t, constT&), since it's ambiguous and chooses the incorrect one no matter what
+				using Vec2::Vec2;//(size_t, signed long const&, Vec2::allocator_type const&);
+				vec(signed long, signed long) = delete;
+				vec(signed long, size_t) = delete;
+				vec(size_t) = delete;
+
+				constexpr ~vec() noexcept = default;
+
+
+				constexpr operator Vec2&&() && noexcept { return std::move(*static_cast<Vec2*>(this)); }
+				constexpr operator Vec2&() const&& = delete;
+			};
+
+			const auto inner = std::vector<signed long>{ size_t(m) + 1 };
+			std::vector<std::vector<signed long>> d{ static_cast<Vec2&&>(std::move(vec{size_t(n) + 1, inner})) };
+			return work_on_d(d);
+		} else {
+			auto** d = reinterpret_cast<signed long**>(allocate_array(sizeof(signed long), m+1, n+1));
+			try {
+				return work_on_d(d);
+			} catch(...) {
+				deallocate_array(reinterpret_cast<void**>(d));
+				throw;
+			}
+		}
+	}
+#endif
+	constexpr auto leven_diff(std::string_view s1, std::string_view s2) noexcept {
+		const size_t 
+			m(s1.size()),
+			n(s2.size());
+
+		if(__builtin_expect(!m, false)) return n;
+		if(__builtin_expect(!n, false)) return m;
+
+		auto&& work_on_d = [&](auto&& costs) {
+			for(size_t i=0;i <= n; i++) costs[i] = i;
+			
+			size_t i{0};
+			for(auto const& c1: s1) {
+				costs[0] = i + 1;
+				size_t	corner	{ i },
+					j	{ 0 };
+				
+				for(auto const& c2: s2) {
+					size_t upper { costs[j+1] };
+					if( c1 == c2 ) costs[j+1] = corner;
+					else {
+						using std::min;
+						size_t t{min(upper, corner)};//upper<corner ? upper : corner
+						costs[j+1] = min(costs[j], t) + 1;
+						
+					}
+					corner = upper;
+					j += 1;
+				}
+				i += 1;
+			}
+			return costs[n];
+		};
+
+		if consteval {
+			return work_on_d(std::vector<size_t>(n + 1));
+		} else {
+			thread_local static std::vector<size_t> d;
+			const size_t n1 = n + 1;
+			if(__builtin_expect(d.size() < n1, false)) d.resize(n1);
+			// We don't need to clear the buffer, it will be reinitialised by `work_on_d()`.
+			return work_on_d(std::span<size_t>{d.begin(), n1});
+		}
+	}
+	template<std::convertible_to<std::string_view> S1, std::convertible_to<std::string_view> S2>
+	constexpr decltype(auto) leven_diff(const S1& sa, const S2& sb) noexcept {
+		using str = std::string_view;
+		return leven_diff(str{sa}, str{sb});
+	}
+
+} }
+#endif
+
+#endif /* _LEVEN_H */
diff --git a/src/leven.cpp b/src/leven.cpp
new file mode 100644
index 0000000..83bd798
--- /dev/null
+++ b/src/leven.cpp
@@ -0,0 +1,12 @@
+
+#include <cstdlib>
+#include <cstring>
+
+#include <leven.h>
+
+namespace exopt {
+	namespace util [[gnu::visibility("internal")]] {	
+		static_assert(leven_diff("hello world", "Hello World") == 2, "Levelshtein distance incorrect for non-matching strings");
+		static_assert(leven_diff("hello world", "hello world") == 0, "Levelshtein distance incorrect for matching strings");
+	}
+}