diff options
Diffstat (limited to 'vendor/pcg-cpp-0.98/include/pcg_extras.hpp')
| -rw-r--r-- | vendor/pcg-cpp-0.98/include/pcg_extras.hpp | 637 |
1 files changed, 637 insertions, 0 deletions
diff --git a/vendor/pcg-cpp-0.98/include/pcg_extras.hpp b/vendor/pcg-cpp-0.98/include/pcg_extras.hpp new file mode 100644 index 00000000..9b2e4e27 --- /dev/null +++ b/vendor/pcg-cpp-0.98/include/pcg_extras.hpp @@ -0,0 +1,637 @@ +/* + * PCG Random Number Generation for C++ + * + * Copyright 2014 Melissa O'Neill <oneill@pcg-random.org> + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + * + * For additional information about the PCG random number generation scheme, + * including its license and other licensing options, visit + * + * http://www.pcg-random.org + */ + +/* + * This file provides support code that is useful for random-number generation + * but not specific to the PCG generation scheme, including: + * - 128-bit int support for platforms where it isn't available natively + * - bit twiddling operations + * - I/O of 128-bit and 8-bit integers + * - Handling the evilness of SeedSeq + * - Support for efficiently producing random numbers less than a given + * bound + */ + +#ifndef PCG_EXTRAS_HPP_INCLUDED +#define PCG_EXTRAS_HPP_INCLUDED 1 + +#include <cinttypes> +#include <cstddef> +#include <cstdlib> +#include <cstring> +#include <cassert> +#include <limits> +#include <iostream> +#include <type_traits> +#include <utility> +#include <locale> +#include <iterator> +#include <utility> + +#ifdef __GNUC__ + #include <cxxabi.h> +#endif + +/* + * Abstractions for compiler-specific directives + */ + +#ifdef __GNUC__ + #define PCG_NOINLINE __attribute__((noinline)) +#else + #define PCG_NOINLINE +#endif + +/* + * Some members of the PCG library use 128-bit math. When compiling on 64-bit + * platforms, both GCC and Clang provide 128-bit integer types that are ideal + * for the job. + * + * On 32-bit platforms (or with other compilers), we fall back to a C++ + * class that provides 128-bit unsigned integers instead. It may seem + * like we're reinventing the wheel here, because libraries already exist + * that support large integers, but most existing libraries provide a very + * generic multiprecision code, but here we're operating at a fixed size. + * Also, most other libraries are fairly heavyweight. So we use a direct + * implementation. Sadly, it's much slower than hand-coded assembly or + * direct CPU support. + * + */ +#if __SIZEOF_INT128__ + namespace pcg_extras { + typedef __uint128_t pcg128_t; + } + #define PCG_128BIT_CONSTANT(high,low) \ + ((pcg128_t(high) << 64) + low) +#else + #include "pcg_uint128.hpp" + namespace pcg_extras { + typedef pcg_extras::uint_x4<uint32_t,uint64_t> pcg128_t; + } + #define PCG_128BIT_CONSTANT(high,low) \ + pcg128_t(high,low) + #define PCG_EMULATED_128BIT_MATH 1 +#endif + + +namespace pcg_extras { + +/* + * We often need to represent a "number of bits". When used normally, these + * numbers are never greater than 128, so an unsigned char is plenty. + * If you're using a nonstandard generator of a larger size, you can set + * PCG_BITCOUNT_T to have it define it as a larger size. (Some compilers + * might produce faster code if you set it to an unsigned int.) + */ + +#ifndef PCG_BITCOUNT_T + typedef uint8_t bitcount_t; +#else + typedef PCG_BITCOUNT_T bitcount_t; +#endif + +/* + * C++ requires us to be able to serialize RNG state by printing or reading + * it from a stream. Because we use 128-bit ints, we also need to be able + * ot print them, so here is code to do so. + * + * This code provides enough functionality to print 128-bit ints in decimal + * and zero-padded in hex. It's not a full-featured implementation. + */ + +template <typename CharT, typename Traits> +std::basic_ostream<CharT,Traits>& +operator<<(std::basic_ostream<CharT,Traits>& out, pcg128_t value) +{ + auto desired_base = out.flags() & out.basefield; + bool want_hex = desired_base == out.hex; + + if (want_hex) { + uint64_t highpart = uint64_t(value >> 64); + uint64_t lowpart = uint64_t(value); + auto desired_width = out.width(); + if (desired_width > 16) { + out.width(desired_width - 16); + } + if (highpart != 0 || desired_width > 16) + out << highpart; + CharT oldfill; + if (highpart != 0) { + out.width(16); + oldfill = out.fill('0'); + } + auto oldflags = out.setf(decltype(desired_base){}, out.showbase); + out << lowpart; + out.setf(oldflags); + if (highpart != 0) { + out.fill(oldfill); + } + return out; + } + constexpr size_t MAX_CHARS_128BIT = 40; + + char buffer[MAX_CHARS_128BIT]; + char* pos = buffer+sizeof(buffer); + *(--pos) = '\0'; + constexpr auto BASE = pcg128_t(10ULL); + do { + auto div = value / BASE; + auto mod = uint32_t(value - (div * BASE)); + *(--pos) = '0' + mod; + value = div; + } while(value != pcg128_t(0ULL)); + return out << pos; +} + +template <typename CharT, typename Traits> +std::basic_istream<CharT,Traits>& +operator>>(std::basic_istream<CharT,Traits>& in, pcg128_t& value) +{ + typename std::basic_istream<CharT,Traits>::sentry s(in); + + if (!s) + return in; + + constexpr auto BASE = pcg128_t(10ULL); + pcg128_t current(0ULL); + bool did_nothing = true; + bool overflow = false; + for(;;) { + CharT wide_ch = in.get(); + if (!in.good()) + break; + auto ch = in.narrow(wide_ch, '\0'); + if (ch < '0' || ch > '9') { + in.unget(); + break; + } + did_nothing = false; + pcg128_t digit(uint32_t(ch - '0')); + pcg128_t timesbase = current*BASE; + overflow = overflow || timesbase < current; + current = timesbase + digit; + overflow = overflow || current < digit; + } + + if (did_nothing || overflow) { + in.setstate(std::ios::failbit); + if (overflow) + current = ~pcg128_t(0ULL); + } + + value = current; + + return in; +} + +/* + * Likewise, if people use tiny rngs, we'll be serializing uint8_t. + * If we just used the provided IO operators, they'd read/write chars, + * not ints, so we need to define our own. We *can* redefine this operator + * here because we're in our own namespace. + */ + +template <typename CharT, typename Traits> +std::basic_ostream<CharT,Traits>& +operator<<(std::basic_ostream<CharT,Traits>&out, uint8_t value) +{ + return out << uint32_t(value); +} + +template <typename CharT, typename Traits> +std::basic_istream<CharT,Traits>& +operator>>(std::basic_istream<CharT,Traits>& in, uint8_t &target) +{ + uint32_t value = 0xdecea5edU; + in >> value; + if (!in && value == 0xdecea5edU) + return in; + if (value > uint8_t(~0)) { + in.setstate(std::ios::failbit); + value = ~0U; + } + target = uint8_t(value); + return in; +} + +/* Unfortunately, the above functions don't get found in preference to the + * built in ones, so we create some more specific overloads that will. + * Ugh. + */ + +inline std::ostream& operator<<(std::ostream& out, uint8_t value) +{ + return pcg_extras::operator<< <char>(out, value); +} + +inline std::istream& operator>>(std::istream& in, uint8_t& value) +{ + return pcg_extras::operator>> <char>(in, value); +} + + + +/* + * Useful bitwise operations. + */ + +/* + * XorShifts are invertable, but they are someting of a pain to invert. + * This function backs them out. It's used by the whacky "inside out" + * generator defined later. + */ + +template <typename itype> +inline itype unxorshift(itype x, bitcount_t bits, bitcount_t shift) +{ + if (2*shift >= bits) { + return x ^ (x >> shift); + } + itype lowmask1 = (itype(1U) << (bits - shift*2)) - 1; + itype highmask1 = ~lowmask1; + itype top1 = x; + itype bottom1 = x & lowmask1; + top1 ^= top1 >> shift; + top1 &= highmask1; + x = top1 | bottom1; + itype lowmask2 = (itype(1U) << (bits - shift)) - 1; + itype bottom2 = x & lowmask2; + bottom2 = unxorshift(bottom2, bits - shift, shift); + bottom2 &= lowmask1; + return top1 | bottom2; +} + +/* + * Rotate left and right. + * + * In ideal world, compilers would spot idiomatic rotate code and convert it + * to a rotate instruction. Of course, opinions vary on what the correct + * idiom is and how to spot it. For clang, sometimes it generates better + * (but still crappy) code if you define PCG_USE_ZEROCHECK_ROTATE_IDIOM. + */ + +template <typename itype> +inline itype rotl(itype value, bitcount_t rot) +{ + constexpr bitcount_t bits = sizeof(itype) * 8; + constexpr bitcount_t mask = bits - 1; +#if PCG_USE_ZEROCHECK_ROTATE_IDIOM + return rot ? (value << rot) | (value >> (bits - rot)) : value; +#else + return (value << rot) | (value >> ((- rot) & mask)); +#endif +} + +template <typename itype> +inline itype rotr(itype value, bitcount_t rot) +{ + constexpr bitcount_t bits = sizeof(itype) * 8; + constexpr bitcount_t mask = bits - 1; +#if PCG_USE_ZEROCHECK_ROTATE_IDIOM + return rot ? (value >> rot) | (value << (bits - rot)) : value; +#else + return (value >> rot) | (value << ((- rot) & mask)); +#endif +} + +/* Unfortunately, both Clang and GCC sometimes perform poorly when it comes + * to properly recognizing idiomatic rotate code, so for we also provide + * assembler directives (enabled with PCG_USE_INLINE_ASM). Boo, hiss. + * (I hope that these compilers get better so that this code can die.) + * + * These overloads will be preferred over the general template code above. + */ +#if PCG_USE_INLINE_ASM && __GNUC__ && (__x86_64__ || __i386__) + +inline uint8_t rotr(uint8_t value, bitcount_t rot) +{ + asm ("rorb %%cl, %0" : "=r" (value) : "0" (value), "c" (rot)); + return value; +} + +inline uint16_t rotr(uint16_t value, bitcount_t rot) +{ + asm ("rorw %%cl, %0" : "=r" (value) : "0" (value), "c" (rot)); + return value; +} + +inline uint32_t rotr(uint32_t value, bitcount_t rot) +{ + asm ("rorl %%cl, %0" : "=r" (value) : "0" (value), "c" (rot)); + return value; +} + +#if __x86_64__ +inline uint64_t rotr(uint64_t value, bitcount_t rot) +{ + asm ("rorq %%cl, %0" : "=r" (value) : "0" (value), "c" (rot)); + return value; +} +#endif // __x86_64__ + +#endif // PCG_USE_INLINE_ASM + + +/* + * The C++ SeedSeq concept (modelled by seed_seq) can fill an array of + * 32-bit integers with seed data, but sometimes we want to produce + * larger or smaller integers. + * + * The following code handles this annoyance. + * + * uneven_copy will copy an array of 32-bit ints to an array of larger or + * smaller ints (actually, the code is general it only needing forward + * iterators). The copy is identical to the one that would be performed if + * we just did memcpy on a standard little-endian machine, but works + * regardless of the endian of the machine (or the weirdness of the ints + * involved). + * + * generate_to initializes an array of integers using a SeedSeq + * object. It is given the size as a static constant at compile time and + * tries to avoid memory allocation. If we're filling in 32-bit constants + * we just do it directly. If we need a separate buffer and it's small, + * we allocate it on the stack. Otherwise, we fall back to heap allocation. + * Ugh. + * + * generate_one produces a single value of some integral type using a + * SeedSeq object. + */ + + /* uneven_copy helper, case where destination ints are less than 32 bit. */ + +template<class SrcIter, class DestIter> +SrcIter uneven_copy_impl( + SrcIter src_first, DestIter dest_first, DestIter dest_last, + std::true_type) +{ + typedef typename std::iterator_traits<SrcIter>::value_type src_t; + typedef typename std::iterator_traits<DestIter>::value_type dest_t; + + constexpr bitcount_t SRC_SIZE = sizeof(src_t); + constexpr bitcount_t DEST_SIZE = sizeof(dest_t); + constexpr bitcount_t DEST_BITS = DEST_SIZE * 8; + constexpr bitcount_t SCALE = SRC_SIZE / DEST_SIZE; + + size_t count = 0; + src_t value; + + while (dest_first != dest_last) { + if ((count++ % SCALE) == 0) + value = *src_first++; // Get more bits + else + value >>= DEST_BITS; // Move down bits + + *dest_first++ = dest_t(value); // Truncates, ignores high bits. + } + return src_first; +} + + /* uneven_copy helper, case where destination ints are more than 32 bit. */ + +template<class SrcIter, class DestIter> +SrcIter uneven_copy_impl( + SrcIter src_first, DestIter dest_first, DestIter dest_last, + std::false_type) +{ + typedef typename std::iterator_traits<SrcIter>::value_type src_t; + typedef typename std::iterator_traits<DestIter>::value_type dest_t; + + constexpr auto SRC_SIZE = sizeof(src_t); + constexpr auto SRC_BITS = SRC_SIZE * 8; + constexpr auto DEST_SIZE = sizeof(dest_t); + constexpr auto SCALE = (DEST_SIZE+SRC_SIZE-1) / SRC_SIZE; + + while (dest_first != dest_last) { + dest_t value(0UL); + unsigned int shift = 0; + + for (size_t i = 0; i < SCALE; ++i) { + value |= dest_t(*src_first++) << shift; + shift += SRC_BITS; + } + + *dest_first++ = value; + } + return src_first; +} + +/* uneven_copy, call the right code for larger vs. smaller */ + +template<class SrcIter, class DestIter> +inline SrcIter uneven_copy(SrcIter src_first, + DestIter dest_first, DestIter dest_last) +{ + typedef typename std::iterator_traits<SrcIter>::value_type src_t; + typedef typename std::iterator_traits<DestIter>::value_type dest_t; + + constexpr bool DEST_IS_SMALLER = sizeof(dest_t) < sizeof(src_t); + + return uneven_copy_impl(src_first, dest_first, dest_last, + std::integral_constant<bool, DEST_IS_SMALLER>{}); +} + +/* generate_to, fill in a fixed-size array of integral type using a SeedSeq + * (actually works for any random-access iterator) + */ + +template <size_t size, typename SeedSeq, typename DestIter> +inline void generate_to_impl(SeedSeq&& generator, DestIter dest, + std::true_type) +{ + generator.generate(dest, dest+size); +} + +template <size_t size, typename SeedSeq, typename DestIter> +void generate_to_impl(SeedSeq&& generator, DestIter dest, + std::false_type) +{ + typedef typename std::iterator_traits<DestIter>::value_type dest_t; + constexpr auto DEST_SIZE = sizeof(dest_t); + constexpr auto GEN_SIZE = sizeof(uint32_t); + + constexpr bool GEN_IS_SMALLER = GEN_SIZE < DEST_SIZE; + constexpr size_t FROM_ELEMS = + GEN_IS_SMALLER + ? size * ((DEST_SIZE+GEN_SIZE-1) / GEN_SIZE) + : (size + (GEN_SIZE / DEST_SIZE) - 1) + / ((GEN_SIZE / DEST_SIZE) + GEN_IS_SMALLER); + // this odd code ^^^^^^^^^^^^^^^^^ is work-around for + // a bug: http://llvm.org/bugs/show_bug.cgi?id=21287 + + if (FROM_ELEMS <= 1024) { + uint32_t buffer[FROM_ELEMS]; + generator.generate(buffer, buffer+FROM_ELEMS); + uneven_copy(buffer, dest, dest+size); + } else { + uint32_t* buffer = (uint32_t*) malloc(GEN_SIZE * FROM_ELEMS); + generator.generate(buffer, buffer+FROM_ELEMS); + uneven_copy(buffer, dest, dest+size); + free(buffer); + } +} + +template <size_t size, typename SeedSeq, typename DestIter> +inline void generate_to(SeedSeq&& generator, DestIter dest) +{ + typedef typename std::iterator_traits<DestIter>::value_type dest_t; + constexpr bool IS_32BIT = sizeof(dest_t) == sizeof(uint32_t); + + generate_to_impl<size>(std::forward<SeedSeq>(generator), dest, + std::integral_constant<bool, IS_32BIT>{}); +} + +/* generate_one, produce a value of integral type using a SeedSeq + * (optionally, we can have it produce more than one and pick which one + * we want) + */ + +template <typename UInt, size_t i = 0UL, size_t N = i+1UL, typename SeedSeq> +inline UInt generate_one(SeedSeq&& generator) +{ + UInt result[N]; + generate_to<N>(std::forward<SeedSeq>(generator), result); + return result[i]; +} + +template <typename RngType> +auto bounded_rand(RngType& rng, typename RngType::result_type upper_bound) + -> typename RngType::result_type +{ + typedef typename RngType::result_type rtype; + rtype threshold = (RngType::max() - RngType::min() + rtype(1) - upper_bound) + % upper_bound; + for (;;) { + rtype r = rng() - RngType::min(); + if (r >= threshold) + return r % upper_bound; + } +} + +template <typename Iter, typename RandType> +void shuffle(Iter from, Iter to, RandType&& rng) +{ + typedef typename std::iterator_traits<Iter>::difference_type delta_t; + auto count = to - from; + while (count > 1) { + delta_t chosen(bounded_rand(rng, count)); + --count; + --to; + using std::swap; + swap(*(from+chosen), *to); + } +} + +/* + * Although std::seed_seq is useful, it isn't everything. Often we want to + * initialize a random-number generator some other way, such as from a random + * device. + * + * Technically, it does not meet the requirements of a SeedSequence because + * it lacks some of the rarely-used member functions (some of which would + * be impossible to provide). However the C++ standard is quite specific + * that actual engines only called the generate method, so it ought not to be + * a problem in practice. + */ + +template <typename RngType> +class seed_seq_from { +private: + RngType rng_; + + typedef uint_least32_t result_type; + +public: + template<typename... Args> + seed_seq_from(Args&&... args) : + rng_(std::forward<Args>(args)...) + { + // Nothing (else) to do... + } + + template<typename Iter> + void generate(Iter start, Iter finish) + { + for (auto i = start; i != finish; ++i) + *i = result_type(rng_()); + } + + constexpr size_t size() const + { + return (sizeof(typename RngType::result_type) > sizeof(result_type) + && RngType::max() > ~size_t(0UL)) + ? ~size_t(0UL) + : size_t(RngType::max()); + } +}; + +/* + * Sometimes you might want a distinct seed based on when the program + * was compiled. That way, a particular instance of the program will + * behave the same way, but when recompiled it'll produce a different + * value. + */ + +template <typename IntType> +struct static_arbitrary_seed { +private: + static constexpr IntType fnv(IntType hash, const char* pos) { + return *pos == '\0' + ? hash + : fnv((hash * IntType(16777619U)) ^ *pos, (pos+1)); + } + +public: + static constexpr IntType value = fnv(IntType(2166136261U ^ sizeof(IntType)), + __DATE__ __TIME__ __FILE__); +}; + +// Sometimes, when debugging or testing, it's handy to be able print the name +// of a (in human-readable form). This code allows the idiom: +// +// cout << printable_typename<my_foo_type_t>() +// +// to print out my_foo_type_t (or its concrete type if it is a synonym) + +template <typename T> +struct printable_typename {}; + +template <typename T> +std::ostream& operator<<(std::ostream& out, printable_typename<T>) { + const char *implementation_typename = typeid(T).name(); +#ifdef __GNUC__ + int status; + const char* pretty_name = + abi::__cxa_demangle(implementation_typename, NULL, NULL, &status); + if (status == 0) + out << pretty_name; + free((void*) pretty_name); + if (status == 0) + return out; +#endif + out << implementation_typename; + return out; +} + +} // namespace pcg_extras + +#endif // PCG_EXTRAS_HPP_INCLUDED |