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Merge pull request #180 from leni536/constexpr-big_int

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Constexpr big_int
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Daniel Lemire 2023-03-03 19:26:29 -05:00 committed by GitHub
commit c487a69c1b
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2 changed files with 155 additions and 71 deletions
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122
include/fast_float/bigint.h
View File

@ -50,7 +50,7 @@ struct stackvec {
stackvec &operator=(stackvec &&other) = delete;
// create stack vector from existing limb span.
stackvec(limb_span s) {
FASTFLOAT_CONSTEXPR20 stackvec(limb_span s) {
FASTFLOAT_ASSERT(try_extend(s));
}
@ -97,13 +97,13 @@ struct stackvec {
}
}
// add items to the vector, from a span, without bounds checking
void extend_unchecked(limb_span s) noexcept {
FASTFLOAT_CONSTEXPR20 void extend_unchecked(limb_span s) noexcept {
limb* ptr = data + length;
::memcpy((void*)ptr, (const void*)s.ptr, sizeof(limb) * s.len());
std::copy_n(s.ptr, s.len(), ptr);
set_len(len() + s.len());
}
// try to add items to the vector, returning if items were added
bool try_extend(limb_span s) noexcept {
FASTFLOAT_CONSTEXPR20 bool try_extend(limb_span s) noexcept {
if (len() + s.len() <= capacity()) {
extend_unchecked(s);
return true;
@ -114,6 +114,7 @@ struct stackvec {
// resize the vector, without bounds checking
// if the new size is longer than the vector, assign value to each
// appended item.
FASTFLOAT_CONSTEXPR20
void resize_unchecked(size_t new_len, limb value) noexcept {
if (new_len > len()) {
size_t count = new_len - len();
@ -126,7 +127,7 @@ struct stackvec {
}
}
// try to resize the vector, returning if the vector was resized.
bool try_resize(size_t new_len, limb value) noexcept {
FASTFLOAT_CONSTEXPR20 bool try_resize(size_t new_len, limb value) noexcept {
if (new_len > capacity()) {
return false;
} else {
@ -160,14 +161,14 @@ uint64_t empty_hi64(bool& truncated) noexcept {
return 0;
}
fastfloat_really_inline
fastfloat_really_inline FASTFLOAT_CONSTEXPR20
uint64_t uint64_hi64(uint64_t r0, bool& truncated) noexcept {
truncated = false;
int shl = leading_zeroes(r0);
return r0 << shl;
}
fastfloat_really_inline
fastfloat_really_inline FASTFLOAT_CONSTEXPR20
uint64_t uint64_hi64(uint64_t r0, uint64_t r1, bool& truncated) noexcept {
int shl = leading_zeroes(r0);
if (shl == 0) {
@ -180,19 +181,19 @@ uint64_t uint64_hi64(uint64_t r0, uint64_t r1, bool& truncated) noexcept {
}
}
fastfloat_really_inline
fastfloat_really_inline FASTFLOAT_CONSTEXPR20
uint64_t uint32_hi64(uint32_t r0, bool& truncated) noexcept {
return uint64_hi64(r0, truncated);
}
fastfloat_really_inline
fastfloat_really_inline FASTFLOAT_CONSTEXPR20
uint64_t uint32_hi64(uint32_t r0, uint32_t r1, bool& truncated) noexcept {
uint64_t x0 = r0;
uint64_t x1 = r1;
return uint64_hi64((x0 << 32) | x1, truncated);
}
fastfloat_really_inline
fastfloat_really_inline FASTFLOAT_CONSTEXPR20
uint64_t uint32_hi64(uint32_t r0, uint32_t r1, uint32_t r2, bool& truncated) noexcept {
uint64_t x0 = r0;
uint64_t x1 = r1;
@ -204,15 +205,16 @@ uint64_t uint32_hi64(uint32_t r0, uint32_t r1, uint32_t r2, bool& truncated) noe
// we want an efficient operation. for msvc, where
// we don't have built-in intrinsics, this is still
// pretty fast.
fastfloat_really_inline
fastfloat_really_inline FASTFLOAT_CONSTEXPR20
limb scalar_add(limb x, limb y, bool& overflow) noexcept {
limb z;
// gcc and clang
#if defined(__has_builtin)
#if __has_builtin(__builtin_add_overflow)
if (!cpp20_and_in_constexpr()) {
overflow = __builtin_add_overflow(x, y, &z);
return z;
}
#endif
#endif
@ -223,7 +225,7 @@ limb scalar_add(limb x, limb y, bool& overflow) noexcept {
}
// multiply two small integers, getting both the high and low bits.
fastfloat_really_inline
fastfloat_really_inline FASTFLOAT_CONSTEXPR20
limb scalar_mul(limb x, limb y, limb& carry) noexcept {
#ifdef FASTFLOAT_64BIT_LIMB
#if defined(__SIZEOF_INT128__)
@ -251,7 +253,8 @@ limb scalar_mul(limb x, limb y, limb& carry) noexcept {
// add scalar value to bigint starting from offset.
// used in grade school multiplication
template <uint16_t size>
inline bool small_add_from(stackvec<size>& vec, limb y, size_t start) noexcept {
inline FASTFLOAT_CONSTEXPR20
bool small_add_from(stackvec<size>& vec, limb y, size_t start) noexcept {
size_t index = start;
limb carry = y;
bool overflow;
@ -268,13 +271,15 @@ inline bool small_add_from(stackvec<size>& vec, limb y, size_t start) noexcept {
// add scalar value to bigint.
template <uint16_t size>
fastfloat_really_inline bool small_add(stackvec<size>& vec, limb y) noexcept {
fastfloat_really_inline FASTFLOAT_CONSTEXPR20
bool small_add(stackvec<size>& vec, limb y) noexcept {
return small_add_from(vec, y, 0);
}
// multiply bigint by scalar value.
template <uint16_t size>
inline bool small_mul(stackvec<size>& vec, limb y) noexcept {
inline FASTFLOAT_CONSTEXPR20
bool small_mul(stackvec<size>& vec, limb y) noexcept {
limb carry = 0;
for (size_t index = 0; index < vec.len(); index++) {
vec[index] = scalar_mul(vec[index], y, carry);
@ -288,6 +293,7 @@ inline bool small_mul(stackvec<size>& vec, limb y) noexcept {
// add bigint to bigint starting from index.
// used in grade school multiplication
template <uint16_t size>
FASTFLOAT_CONSTEXPR20
bool large_add_from(stackvec<size>& x, limb_span y, size_t start) noexcept {
// the effective x buffer is from `xstart..x.len()`, so exit early
// if we can't get that current range.
@ -318,12 +324,14 @@ bool large_add_from(stackvec<size>& x, limb_span y, size_t start) noexcept {
// add bigint to bigint.
template <uint16_t size>
fastfloat_really_inline bool large_add_from(stackvec<size>& x, limb_span y) noexcept {
fastfloat_really_inline FASTFLOAT_CONSTEXPR20
bool large_add_from(stackvec<size>& x, limb_span y) noexcept {
return large_add_from(x, y, 0);
}
// grade-school multiplication algorithm
template <uint16_t size>
FASTFLOAT_CONSTEXPR20
bool long_mul(stackvec<size>& x, limb_span y) noexcept {
limb_span xs = limb_span(x.data, x.len());
stackvec<size> z(xs);
@ -352,6 +360,7 @@ bool long_mul(stackvec<size>& x, limb_span y) noexcept {
// grade-school multiplication algorithm
template <uint16_t size>
FASTFLOAT_CONSTEXPR20
bool large_mul(stackvec<size>& x, limb_span y) noexcept {
if (y.len() == 1) {
FASTFLOAT_TRY(small_mul(x, y[0]));
@ -361,21 +370,52 @@ bool large_mul(stackvec<size>& x, limb_span y) noexcept {
return true;
}
template <typename = void>
struct pow5_tables {
static constexpr uint32_t large_step = 135;
static constexpr uint64_t small_power_of_5[] = {
1UL, 5UL, 25UL, 125UL, 625UL, 3125UL, 15625UL, 78125UL, 390625UL,
1953125UL, 9765625UL, 48828125UL, 244140625UL, 1220703125UL,
6103515625UL, 30517578125UL, 152587890625UL, 762939453125UL,
3814697265625UL, 19073486328125UL, 95367431640625UL, 476837158203125UL,
2384185791015625UL, 11920928955078125UL, 59604644775390625UL,
298023223876953125UL, 1490116119384765625UL, 7450580596923828125UL,
};
#ifdef FASTFLOAT_64BIT_LIMB
constexpr static limb large_power_of_5[] = {
1414648277510068013UL, 9180637584431281687UL, 4539964771860779200UL,
10482974169319127550UL, 198276706040285095UL};
#else
constexpr static limb large_power_of_5[] = {
4279965485U, 329373468U, 4020270615U, 2137533757U, 4287402176U,
1057042919U, 1071430142U, 2440757623U, 381945767U, 46164893U};
#endif
};
template <typename T>
constexpr uint32_t pow5_tables<T>::large_step;
template <typename T>
constexpr uint64_t pow5_tables<T>::small_power_of_5[];
template <typename T>
constexpr limb pow5_tables<T>::large_power_of_5[];
// big integer type. implements a small subset of big integer
// arithmetic, using simple algorithms since asymptotically
// faster algorithms are slower for a small number of limbs.
// all operations assume the big-integer is normalized.
struct bigint {
struct bigint : pow5_tables<> {
// storage of the limbs, in little-endian order.
stackvec<bigint_limbs> vec;
bigint(): vec() {}
FASTFLOAT_CONSTEXPR20 bigint(): vec() {}
bigint(const bigint &) = delete;
bigint &operator=(const bigint &) = delete;
bigint(bigint &&) = delete;
bigint &operator=(bigint &&other) = delete;
bigint(uint64_t value): vec() {
FASTFLOAT_CONSTEXPR20 bigint(uint64_t value): vec() {
#ifdef FASTFLOAT_64BIT_LIMB
vec.push_unchecked(value);
#else
@ -387,7 +427,7 @@ struct bigint {
// get the high 64 bits from the vector, and if bits were truncated.
// this is to get the significant digits for the float.
uint64_t hi64(bool& truncated) const noexcept {
FASTFLOAT_CONSTEXPR20 uint64_t hi64(bool& truncated) const noexcept {
#ifdef FASTFLOAT_64BIT_LIMB
if (vec.len() == 0) {
return empty_hi64(truncated);
@ -419,7 +459,7 @@ struct bigint {
// positive, this is larger, otherwise they are equal.
// the limbs are stored in little-endian order, so we
// must compare the limbs in ever order.
int compare(const bigint& other) const noexcept {
FASTFLOAT_CONSTEXPR20 int compare(const bigint& other) const noexcept {
if (vec.len() > other.vec.len()) {
return 1;
} else if (vec.len() < other.vec.len()) {
@ -440,7 +480,7 @@ struct bigint {
// shift left each limb n bits, carrying over to the new limb
// returns true if we were able to shift all the digits.
bool shl_bits(size_t n) noexcept {
FASTFLOAT_CONSTEXPR20 bool shl_bits(size_t n) noexcept {
// Internally, for each item, we shift left by n, and add the previous
// right shifted limb-bits.
// For example, we transform (for u8) shifted left 2, to:
@ -466,7 +506,7 @@ struct bigint {
}
// move the limbs left by `n` limbs.
bool shl_limbs(size_t n) noexcept {
FASTFLOAT_CONSTEXPR20 bool shl_limbs(size_t n) noexcept {
FASTFLOAT_DEBUG_ASSERT(n != 0);
if (n + vec.len() > vec.capacity()) {
return false;
@ -487,7 +527,7 @@ struct bigint {
}
// move the limbs left by `n` bits.
bool shl(size_t n) noexcept {
FASTFLOAT_CONSTEXPR20 bool shl(size_t n) noexcept {
size_t rem = n % limb_bits;
size_t div = n / limb_bits;
if (rem != 0) {
@ -500,7 +540,7 @@ struct bigint {
}
// get the number of leading zeros in the bigint.
int ctlz() const noexcept {
FASTFLOAT_CONSTEXPR20 int ctlz() const noexcept {
if (vec.is_empty()) {
return 0;
} else {
@ -515,45 +555,27 @@ struct bigint {
}
// get the number of bits in the bigint.
int bit_length() const noexcept {
FASTFLOAT_CONSTEXPR20 int bit_length() const noexcept {
int lz = ctlz();
return int(limb_bits * vec.len()) - lz;
}
bool mul(limb y) noexcept {
FASTFLOAT_CONSTEXPR20 bool mul(limb y) noexcept {
return small_mul(vec, y);
}
bool add(limb y) noexcept {
FASTFLOAT_CONSTEXPR20 bool add(limb y) noexcept {
return small_add(vec, y);
}
// multiply as if by 2 raised to a power.
bool pow2(uint32_t exp) noexcept {
FASTFLOAT_CONSTEXPR20 bool pow2(uint32_t exp) noexcept {
return shl(exp);
}
// multiply as if by 5 raised to a power.
bool pow5(uint32_t exp) noexcept {
FASTFLOAT_CONSTEXPR20 bool pow5(uint32_t exp) noexcept {
// multiply by a power of 5
static constexpr uint32_t large_step = 135;
static constexpr uint64_t small_power_of_5[] = {
1UL, 5UL, 25UL, 125UL, 625UL, 3125UL, 15625UL, 78125UL, 390625UL,
1953125UL, 9765625UL, 48828125UL, 244140625UL, 1220703125UL,
6103515625UL, 30517578125UL, 152587890625UL, 762939453125UL,
3814697265625UL, 19073486328125UL, 95367431640625UL, 476837158203125UL,
2384185791015625UL, 11920928955078125UL, 59604644775390625UL,
298023223876953125UL, 1490116119384765625UL, 7450580596923828125UL,
};
#ifdef FASTFLOAT_64BIT_LIMB
constexpr static limb large_power_of_5[] = {
1414648277510068013UL, 9180637584431281687UL, 4539964771860779200UL,
10482974169319127550UL, 198276706040285095UL};
#else
constexpr static limb large_power_of_5[] = {
4279965485U, 329373468U, 4020270615U, 2137533757U, 4287402176U,
1057042919U, 1071430142U, 2440757623U, 381945767U, 46164893U};
#endif
size_t large_length = sizeof(large_power_of_5) / sizeof(limb);
limb_span large = limb_span(large_power_of_5, large_length);
while (exp >= large_step) {
@ -579,7 +601,7 @@ struct bigint {
}
// multiply as if by 10 raised to a power.
bool pow10(uint32_t exp) noexcept {
FASTFLOAT_CONSTEXPR20 bool pow10(uint32_t exp) noexcept {
FASTFLOAT_TRY(pow5(exp));
return pow2(exp);
}

100
include/fast_float/float_common.h
View File

@ -7,6 +7,25 @@
#include <cstring>
#include <type_traits>
#ifdef __has_include
#if __has_include(<version>)
#include <version>
#endif
#endif
#if __cpp_lib_bit_cast >= 201806L
#include <bit>
#define FASTFLOAT_HAS_BIT_CAST 1
#else
#define FASTFLOAT_HAS_BIT_CAST 0
#endif
#if __cpp_lib_is_constant_evaluated >= 201811L
#define FASTFLOAT_HAS_IS_CONSTANT_EVALUATED 1
#else
#define FASTFLOAT_HAS_IS_CONSTANT_EVALUATED 0
#endif
#if (defined(__x86_64) || defined(__x86_64__) || defined(_M_X64) \
|| defined(__amd64) || defined(__aarch64__) || defined(_M_ARM64) \
|| defined(__MINGW64__) \
@ -98,8 +117,25 @@
#define FASTFLOAT_CONSTEXPR14
#endif
// Testing for relevant C++20 constexpr library features
#if FASTFLOAT_HAS_IS_CONSTANT_EVALUATED \
&& FASTFLOAT_HAS_BIT_CAST \
&& __cpp_lib_constexpr_algorithms >= 201806L /*For std::copy and std::fill*/
#define FASTFLOAT_CONSTEXPR20 constexpr
#else
#define FASTFLOAT_CONSTEXPR20
#endif
namespace fast_float {
fastfloat_really_inline constexpr bool cpp20_and_in_constexpr() {
#if FASTFLOAT_HAS_IS_CONSTANT_EVALUATED
return std::is_constant_evaluated();
#else
return false;
#endif
}
// Compares two ASCII strings in a case insensitive manner.
inline FASTFLOAT_CONSTEXPR14 bool
fastfloat_strncasecmp(const char *input1, const char *input2, size_t length) {
@ -139,9 +175,27 @@ struct value128 {
constexpr value128() : low(0), high(0) {}
};
/* Helper C++11 constexpr generic implementation of leading_zeroes */
fastfloat_really_inline constexpr
int leading_zeroes_generic(uint64_t input_num, int last_bit = 0) {
return (
((input_num & uint64_t(0xffffffff00000000)) && (input_num >>= 32, last_bit |= 32)),
((input_num & uint64_t( 0xffff0000)) && (input_num >>= 16, last_bit |= 16)),
((input_num & uint64_t( 0xff00)) && (input_num >>= 8, last_bit |= 8)),
((input_num & uint64_t( 0xf0)) && (input_num >>= 4, last_bit |= 4)),
((input_num & uint64_t( 0xc)) && (input_num >>= 2, last_bit |= 2)),
((input_num & uint64_t( 0x2)) && (input_num >>= 1, last_bit |= 1)),
63 - last_bit
);
}
/* result might be undefined when input_num is zero */
fastfloat_really_inline int leading_zeroes(uint64_t input_num) {
fastfloat_really_inline FASTFLOAT_CONSTEXPR20
int leading_zeroes(uint64_t input_num) {
assert(input_num > 0);
if (cpp20_and_in_constexpr()) {
return leading_zeroes_generic(input_num);
}
#ifdef FASTFLOAT_VISUAL_STUDIO
#if defined(_M_X64) || defined(_M_ARM64)
unsigned long leading_zero = 0;
@ -150,31 +204,20 @@ fastfloat_really_inline int leading_zeroes(uint64_t input_num) {
_BitScanReverse64(&leading_zero, input_num);
return (int)(63 - leading_zero);
#else
int last_bit = 0;
if(input_num & uint64_t(0xffffffff00000000)) input_num >>= 32, last_bit |= 32;
if(input_num & uint64_t( 0xffff0000)) input_num >>= 16, last_bit |= 16;
if(input_num & uint64_t( 0xff00)) input_num >>= 8, last_bit |= 8;
if(input_num & uint64_t( 0xf0)) input_num >>= 4, last_bit |= 4;
if(input_num & uint64_t( 0xc)) input_num >>= 2, last_bit |= 2;
if(input_num & uint64_t( 0x2)) input_num >>= 1, last_bit |= 1;
return 63 - last_bit;
return leading_zeroes_generic(input_num);
#endif
#else
return __builtin_clzll(input_num);
#endif
}
#ifdef FASTFLOAT_32BIT
// slow emulation routine for 32-bit
fastfloat_really_inline constexpr uint64_t emulu(uint32_t x, uint32_t y) {
return x * (uint64_t)y;
}
// slow emulation routine for 32-bit
#if !defined(__MINGW64__)
fastfloat_really_inline constexpr uint64_t _umul128(uint64_t ab, uint64_t cd,
uint64_t *hi) {
fastfloat_really_inline FASTFLOAT_CONSTEXPR14
uint64_t umul128_generic(uint64_t ab, uint64_t cd, uint64_t *hi) {
uint64_t ad = emulu((uint32_t)(ab >> 32), (uint32_t)cd);
uint64_t bd = emulu((uint32_t)ab, (uint32_t)cd);
uint64_t adbc = ad + emulu((uint32_t)ab, (uint32_t)(cd >> 32));
@ -184,14 +227,28 @@ fastfloat_really_inline constexpr uint64_t _umul128(uint64_t ab, uint64_t cd,
(adbc_carry << 32) + !!(lo < bd);
return lo;
}
#ifdef FASTFLOAT_32BIT
// slow emulation routine for 32-bit
#if !defined(__MINGW64__)
fastfloat_really_inline FASTFLOAT_CONSTEXPR14
uint64_t _umul128(uint64_t ab, uint64_t cd, uint64_t *hi) {
return umul128_generic(ab, cd, hi);
}
#endif // !__MINGW64__
#endif // FASTFLOAT_32BIT
// compute 64-bit a*b
fastfloat_really_inline value128 full_multiplication(uint64_t a,
uint64_t b) {
fastfloat_really_inline FASTFLOAT_CONSTEXPR20
value128 full_multiplication(uint64_t a, uint64_t b) {
if (cpp20_and_in_constexpr()) {
value128 answer;
answer.low = umul128_generic(a, b, &answer.high);
return answer;
}
value128 answer;
#if defined(_M_ARM64) && !defined(__MINGW32__)
// ARM64 has native support for 64-bit multiplications, no need to emulate
@ -205,7 +262,7 @@ fastfloat_really_inline value128 full_multiplication(uint64_t a,
answer.low = uint64_t(r);
answer.high = uint64_t(r >> 64);
#else
#error Not implemented
answer.low = umul128_generic(a, b, &answer.high);
#endif
return answer;
}
@ -442,12 +499,17 @@ template <> inline constexpr binary_format<double>::equiv_uint
}
template<typename T>
fastfloat_really_inline void to_float(bool negative, adjusted_mantissa am, T &value) {
fastfloat_really_inline FASTFLOAT_CONSTEXPR20
void to_float(bool negative, adjusted_mantissa am, T &value) {
using uint = typename binary_format<T>::equiv_uint;
uint word = (uint)am.mantissa;
word |= uint(am.power2) << binary_format<T>::mantissa_explicit_bits();
word |= uint(negative) << binary_format<T>::sign_index();
#if FASTFLOAT_HAS_BIT_CAST
value = std::bit_cast<T>(word);
#else
::memcpy(&value, &word, sizeof(T));
#endif
}
#if FASTFLOAT_SKIP_WHITE_SPACE // disabled by default