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Parameterized fp on significand type

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This commit is contained in:
Victor Zverovich 2022-02-20 11:33:16 -08:00
parent cf940ae82e
commit 4fcacea354
2 changed files with 22 additions and 15 deletions
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23
include/fmt/format-inl.h
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@ -223,18 +223,20 @@ template <typename Float> constexpr int num_significand_bits() {
}
// A floating-point number f * pow(2, e).
struct fp {
uint64_t f;
template <typename F> struct basic_fp {
F f;
int e;
static constexpr const int num_significand_bits = bits<decltype(f)>::value;
static constexpr const int num_significand_bits = bits<F>::value;
constexpr fp() : f(0), e(0) {}
constexpr fp(uint64_t f_val, int e_val) : f(f_val), e(e_val) {}
constexpr basic_fp() : f(0), e(0) {}
constexpr basic_fp(uint64_t f_val, int e_val) : f(f_val), e(e_val) {}
// Constructs fp from an IEEE754 floating-point number. It is a template to
// prevent compile errors on systems where n is not IEEE754.
template <typename Float> explicit FMT_CONSTEXPR fp(Float n) { assign(n); }
template <typename Float> explicit FMT_CONSTEXPR basic_fp(Float n) {
assign(n);
}
template <typename Float>
using is_supported = bool_constant<std::numeric_limits<Float>::digits <= 64>;
@ -272,8 +274,11 @@ struct fp {
}
};
using fp = basic_fp<unsigned long long>;
// Normalizes the value converted from double and multiplied by (1 << SHIFT).
template <int SHIFT = 0> FMT_CONSTEXPR fp normalize(fp value) {
template <int SHIFT = 0, typename F>
FMT_CONSTEXPR basic_fp<F> normalize(basic_fp<F> value) {
// Handle subnormals.
const uint64_t implicit_bit = 1ULL << num_significand_bits<double>();
const auto shifted_implicit_bit = implicit_bit << SHIFT;
@ -289,7 +294,9 @@ template <int SHIFT = 0> FMT_CONSTEXPR fp normalize(fp value) {
return value;
}
inline bool operator==(fp x, fp y) { return x.f == y.f && x.e == y.e; }
template <typename F> inline bool operator==(basic_fp<F> x, basic_fp<F> y) {
return x.f == y.f && x.e == y.e;
}
// Computes lhs * rhs / pow(2, 64) rounded to nearest with half-up tie breaking.
FMT_CONSTEXPR inline uint64_t multiply(uint64_t lhs, uint64_t rhs) {

14
test/format-impl-test.cc
View File

@ -190,14 +190,14 @@ TEST(fp_test, get_cached_power) {
using limits = std::numeric_limits<double>;
for (auto exp = limits::min_exponent; exp <= limits::max_exponent; ++exp) {
int dec_exp = 0;
auto fp = fmt::detail::get_cached_power(exp, dec_exp);
bigint exact, cache(fp.f);
auto power = fmt::detail::get_cached_power(exp, dec_exp);
bigint exact, cache(power.f);
if (dec_exp >= 0) {
exact.assign_pow10(dec_exp);
if (fp.e <= 0)
exact <<= -fp.e;
if (power.e <= 0)
exact <<= -power.e;
else
cache <<= fp.e;
cache <<= power.e;
exact.align(cache);
cache.align(exact);
auto exact_str = fmt::format("{}", exact);
@ -211,9 +211,9 @@ TEST(fp_test, get_cached_power) {
EXPECT_EQ(diff, 0);
} else {
cache.assign_pow10(-dec_exp);
cache *= fp.f + 1; // Inexact check.
cache *= power.f + 1; // Inexact check.
exact.assign(1);
exact <<= -fp.e;
exact <<= -power.e;
exact.align(cache);
auto exact_str = fmt::format("{}", exact);
auto cache_str = fmt::format("{}", cache);